Teriparatide (PTH 1-34)

The first 34 amino acids of the body's own parathyroid hormone, made in a lab. The sequence is verified against UniProt P01270, where mature PTH occupies positions 32–115 of the precursor; positions 32–65 match the teriparatide sequence exactly.

Sold as

Injection under the skin.

Legal status in the EU

An approved prescription medicine in the EU since 2003 for osteoporosis in post-menopausal women, in men at increased risk of fracture, and during long-term steroid treatment. Biosimilars exist, for example Movymia, approved on 11 January 2017 with Forsteo as the reference medicine.

It switches on the PTH-1 receptor on bone-building cells. Continuously raised parathyroid hormone breaks bone down, but giving it in short bursts does the opposite — bone building outpaces bone breakdown. That is what separates teriparatide from bisphosphonates, which instead slow the breakdown.

Part of the bodyWhat happensHow it is knownKind of evidence

Bone, and why the injection has to be daily

This is the whole drug in one sentence: the same hormone does opposite things depending on whether it arrives as a spike or as a steady level. When parathyroid hormone stays high all the time — which is what happens in the condition called overactive parathyroid glands — bone is broken down and lost. When it arrives once a day and is gone again within hours, the cells that build bone get the upper hand over the cells that break it down, and new bone is laid on the surfaces of existing bone. Teriparatide leaves the body fast enough to make that spike: after an injection under the skin its half-life is about an hour. A slow-release version of the same molecule would strip bone rather than build it.

The European product information states directly that the skeletal effects depend on the pattern of exposure, and that once-daily injection lays down new bone by favouring the building cells over the breaking-down cells. The one-hour half-life after injection under the skin is measured and printed in the same document. The opposite effect of continuously raised hormone is the textbook description of overactive parathyroid glands, set out in a 2017 review of teriparatide.

Measured in people

Source [07]Source [08]

The spine

The spine is where the drug does most of its work, and it is where the bone is of the spongy kind that responds fastest. The measured density of the lower spine on a scan starts rising within three months and keeps rising for the full two years. Nothing about this is felt: a person notices only that fewer bones break.

Measured by scan in 1,085 postmenopausal women over a median of 19 months. Lower-spine density rose 9.7% on teriparatide against 1.1% on dummy injections. Rises were statistically significant by three months. 96% of women gained lower-spine density, 72% gained at least 5% and 44% gained 10% or more. In a separate study of 503 women with severe osteoporosis treated up to 24 months, lower-spine density rose 10.5% from the start — that study had no comparison group, so the figure includes whatever the calcium, the vitamin D and the passage of time did — and 1.4% of the rise came in the last six months alone.

Measured in people

Source [07]Source [09]

The hip, and the wrist

Away from the spine the picture is weaker and, at one site, it goes the wrong way. Hip density rises, but by a fraction of what the spine gains. At the shaft of the forearm bone — where the bone is dense and tube-like rather than spongy — density falls slightly on the drug. The forearm is also where the drug's effect is most often misread: the fall is small, it is thought to reflect bone being remodelled rather than lost, and it has not translated into more wrist fractures. It has never been shown to prevent a broken hip.

Measured by scan in the same 1,085 women over a median of 19 months. Total hip density rose 2.6% against a fall of 1.0% on dummy injections; the neck of the thigh bone rose 2.8% against a fall of 0.7%; the shaft of the forearm bone fell 2.1% on the drug against a fall of 1.3% on dummy injections. The European product information states flatly that a significant reduction in hip fractures has not been demonstrated. In the trial, hip fractures happened to 0.2% of women on the drug and 0.7% on dummy injections — real numbers, but far too few to settle anything.

Measured in people

Source [07]Source [09]

Calcium in the blood

Every injection pushes blood calcium up for a few hours and then it comes back down. That is not a side effect — it is the hormone doing what parathyroid hormone does, pulling calcium out of bone and holding on to more of it in the kidney. It matters for two practical reasons. A blood calcium test taken too soon after an injection reads high and means nothing, and anyone whose calcium is already high before starting should not take the drug at all.

Measured directly: blood calcium peaks 4 to 6 hours after each dose and is back to where it started by 16 to 24 hours. The European product information instructs that blood samples for calcium be taken at least 16 hours after the most recent injection, and says routine calcium monitoring is not required. At least one transient high reading in the 4 to 6 hours after a dose happened in 11% of women and 6% of men on the drug, against 2% of women and 0% of men on dummy injections; it was confirmed on a repeat measurement in 3% of women and 1% of men.

Measured in people

Source [07]Source [09]

Blood pressure when you stand up

In the first few doses some people's blood pressure drops when they get up, and they feel faint or actually faint. It comes on within about four hours of the injection, settles by itself in minutes to hours, and does not usually mean stopping. It matters more here than it would in most people, because everyone taking this drug has bones that break easily and a faint means a fall.

Seen in 5% of healthy volunteers in short-term studies of the drug's action. In the osteoporosis trials, low blood pressure and fainting were both listed as common — fainting was reported by 2.6% of 691 people on the drug against 1.4% of 691 on dummy injections. Both labels instruct that the first doses be given somewhere the person can sit or lie down.

Measured in people

Source [07]Source [09]

Arms, legs and back, in the hours after the injection

Pain in a limb is the single most common thing recorded on this drug — more common than feeling sick. Leg cramps come with it. Separately, and more sharply, some people get a cramp or pain in the back within minutes of injecting, which then eases. The European regulator lists back cramp and pain as uncommon but attaches a footnote saying serious cases have been reported within minutes of the injection, which is an unusual thing for a product information to say about an uncommon event.

The European product information classes pain in a limb as very common — at least 1 person in 10 — and muscle cramps as common. The US label counts joint pain in 10.1% of 691 people on the drug against 8.4% of 691 on dummy injections, and leg cramps in 2.6% against 1.3%. The footnote about back cramp within minutes of injecting is in the European table itself. On the US regulator's public side-effect file, pain in an extremity is the third most reported term for teriparatide with 8,349 reports and back pain the eighth with 5,919.

Measured in people

Source [07]Source [09]Source [10]

Bone in rats, given the drug for most of their lives

This is the finding that shaped the drug's first eighteen years on the market, and it belongs in the body section because it is a real biological effect, not a rumour. Rats given daily injections for most of their lifespan grew far more bone than normal, and a proportion of them developed a rare bone cancer. The effect depended on both how much and for how long. It has not been found in monkeys, and it has not been found in people — but it happened, and it happened at doses not far above the human one.

Two carcinogenicity studies in Fischer 344 rats. In the first, rats were given 5, 30 or 75 micrograms per kilogram per day for 24 months from two months of age — 3, 20 and 60 times the exposure a person gets from a 20-microgram dose. Bone cancer appeared at every dose and reached 40% to 50% of animals in the highest group. No untreated control rat developed one. The second study showed the effect depended on duration and on the age at which treatment started: no tumours appeared in mature six-month-old rats given the lowest dose for 6 or 20 months. No bone tumours appeared in monkeys whose ovaries had been removed and who were treated for 18 months and then followed for three years.

Only seen in animals

Source [07]Source [09]

The Fracture Prevention Trial (Neer et al., NEJM 2001) randomised 1,637 post-menopausal women with at least one previous spinal fracture, followed for a median of 21 months. In the group given 20 micrograms, new spinal fractures occurred in 5 per cent versus 14 per cent on placebo (relative risk 0.35; 95 per cent confidence interval 0.22–0.55), and fractures elsewhere in 3 versus 6 per cent (relative risk 0.47; 0.25–0.88). The European regulator states that an effect on hip fracture has not been shown. Forsteo was approved in the EU on 10 June 2003.

Hours, then months, then a cliff. Each injection raises blood calcium to a peak at 4 to 6 hours and it is back to baseline by 16 to 24 hours; the drug itself has a half-life of about an hour after injection under the skin. That daily spike is the treatment. Bone-building markers in the blood rise within days of the first injection, peak somewhere between 6 and 12 months, and stay above where they started for the whole two years; the markers of bone being broken down rise later and catch up, which is why the gap between building and breaking — and with it the rate of gain — narrows as the course goes on. Bone density at the lower spine is measurably up by three months and keeps climbing to the end: in women treated for a full 24 months, 1.4% of the total 10.5% spine gain came in the last six months alone. Fractures follow more slowly. In ordinary European practice the odds of a break coming to clinical attention were 47% lower in months 12 to 18 than in the first six months, with no further significant drop in months 18 to 24. Back pain improves through the course and keeps improving afterwards: on a 100 mm scale it went from 50.2 mm at the start to 27.8 mm at 24 months and 22.3 mm at 42 months. Then the drug stops, and this is the part a reader most needs to plan for. Bone loss after stopping is faster than ordinary ageing — a review of the discontinuation studies puts it at 2.2% to 4.4% at the lower spine in the first year, against the 0.5% to 1.0% a year an untreated postmenopausal woman loses. In the women who started a bone-preserving drug promptly, density barely moved: 1.2% down at the spine and 0.8% at the hip over about 15 months, against 10.0% and 4.5% in those who took nothing. The fracture protection lasts longer than the density: over a median of 18 months after the pivotal trial ended there were still 41% fewer women with a new spinal break than in the group that had been on dummy injections, although other treatments were allowed in that period. Going back for a second course later works less well: after a year off, the same people gained 5.2% at the spine against 12.5% the first time, and 0.2% at the neck of the thigh bone against 2.8%.

What was measuredWhat happenedIn whomHow it is known

New breaks in the spine, against a dummy injection

5.0% of women on teriparatide had at least one new break in a spinal bone against 14.3% on dummy injections — a relative risk of 0.35 (95% CI 0.22 to 0.55). Two or more new breaks: 1.1% against 4.9% (relative risk 0.23, 95% CI 0.09 to 0.60). The regulator states that 11 women had to be treated for a median of 19 months to prevent one or more new spinal breaks. Most of these breaks are found on an X-ray rather than felt, which is why the trial X-rayed everybody at the start and at the end.

1,637 postmenopausal women, mean age 69.5 years, 90% of whom already had at least one spinal break; fractures counted in the 444 on the drug and 448 on dummy injections who had both X-rays; median 19 months of treatment

Measured in people

Source [01]Source [07]

Breaks anywhere other than the spine, against a dummy injection

2.6% of women on the drug broke a bone somewhere other than the spine in a fall from standing height or less, against 5.5% on dummy injections (relative risk 0.47, 95% CI 0.25 to 0.87). Counting only the breaks that matter most — hip, wrist, upper arm, ribs and pelvis — 1.5% against 3.9% (relative risk 0.38, 95% CI 0.17 to 0.86). The New England Journal paper rounds the same result to 3% against 6%.

The same 1,637 women, median 19 months of treatment

Measured in people

Source [01]Source [07]

Broken hips specifically

Not shown, and the regulator says so in the product information rather than leaving it to be inferred. In the pivotal trial, 0.2% of women on the drug broke a hip against 0.7% on dummy injections — a difference in the right direction built on a handful of events, in a trial that was stopped early and was never large enough to answer the question. A 2025 network analysis of 17 studies found abaloparatide, a close relative of teriparatide, did better than teriparatide on hip fractures (odds ratio 0.81, 95% CI 0.71 to 0.93) and on breaks outside the spine (odds ratio 0.87, 95% CI 0.80 to 0.95).

The 1,637-woman trial for the direct figures; 17 studies — 11 randomised trials and 6 real-world studies — for the comparison with abaloparatide

Measured in people

Source [07]Source [09]Source [11]

Head to head against risedronate, an ordinary weekly bone tablet

This is the most useful comparison on the record, because almost nobody is choosing between teriparatide and nothing. New breaks in the spine happened to 28 of 516 women on teriparatide (5.4%) against 64 of 533 on risedronate (12.0%) — a relative risk of 0.44 (95% CI 0.29 to 0.68, p<0.0001). Breaks that came to clinical attention, spine or elsewhere: 30 of 680 (4.8%) against 61 of 680 (9.8%), hazard ratio 0.48 (95% CI 0.32 to 0.74, p=0.0009). Breaks outside the spine went the same way but the range crossed no difference, so that comparison answered nothing: 4.0% against 6.1% (hazard ratio 0.66, p=0.10).

1,360 postmenopausal women with established osteoporosis, mean age 72.1 years, a median of 2 existing spinal breaks; 57.9% had already been on a bone tablet and 18.8% were on long-term steroids; 24 months, 1,013 (74.5%) completed. Funded by Lilly, which makes the drug.

Measured in people

Source [07]Source [12]

Head to head against alendronate, in people on long-term steroid tablets

Lower-spine density rose 7.2% on teriparatide against 3.4% on alendronate at 18 months (p<0.001); total hip 3.6% against 2.2% (p<0.01); the neck of the thigh bone 3.7% against 2.1% (p<0.05). At 36 months, new spinal breaks had happened to 3 of 173 people on teriparatide (1.7%) against 13 of 169 on alendronate (7.7%), p=0.01. Breaks elsewhere were identical: 16 of 214 (7.5%) against 15 of 214 (7.0%), p=0.84.

428 men and women taking steroid tablets — the equivalent of 5 mg of prednisone a day or more — for at least 3 months — 277 postmenopausal women, 67 premenopausal women and 83 men; 28% already had a spinal break; 69% completed the 18-month main phase

Measured in people

Source [07]

Head to head against romosozumab, in women coming off bone tablets

Teriparatide lost. Over 12 months total hip density rose 2.6% on romosozumab (95% CI 2.2 to 3.0) and fell 0.6% on teriparatide (95% CI −1.0 to −0.2), a difference of 3.2 percentage points (95% CI 2.7 to 3.8, p<0.0001). This is the clearest published demonstration that years of prior bone tablets blunt what teriparatide can do, particularly at the hip. Side effects were broadly similar between the groups, with one exception: high blood calcium in 10% on teriparatide against under 1% on romosozumab.

436 postmenopausal women aged 55 to 90 who had been on bone tablets for at least three years; 206 analysed on romosozumab and 209 on teriparatide; 12 months, open-label

Measured in people

Source [13]

Back pain

New or worsening back pain was about a third less likely on teriparatide than on whatever it was compared with: relative risk 0.66 (95% CI 0.55 to 0.80) for any back pain, 0.60 (95% CI 0.48 to 0.75) for moderate or severe, and 0.44 (95% CI 0.28 to 0.68) for severe. The comparators were dummy injections in two trials, alendronate in two, and hormone replacement therapy in one. There was no difference between the 20 and 40 microgram amounts.

5 randomised double-blind trials pooled — four in postmenopausal women with osteoporosis, one in men

Measured in people

Source [14]

Bone density and fractures in men

Density rose; fractures were not answered. After 12 months, lower-spine density was 5% higher and total hip 1% higher than on dummy injections. The regulator states plainly that no significant effect on fracture rates was demonstrated — the trial was too short and too small, with a median treatment exposure of about 10 months. This is the reason the European indication for men is worded as treatment of osteoporosis in men at increased risk of fracture rather than as fracture prevention.

437 men, mean age 58.7 years, with either low testosterone or osteoporosis of no known cause; 151 received the 20-microgram amount; at the start 35% had a spinal break and 59% a break elsewhere

Measured in people

Source [07]Source [09]

What happened after the injections stopped

The protection outlasted the drug, but the bone density did not. In the follow-up of the pivotal trial, over a median of 18 months after stopping there were 41% fewer people with at least one new spinal break than in the group that had been on dummy injections (p=0.004) — although other bone treatments were allowed during that period, so this is not a clean picture of stopping and taking nothing. On density the picture is clearer and worse: a review of the field puts the loss at the lower spine at 2.2% to 4.4% in the first year off the drug, against the 0.5% to 1.0% a year an untreated postmenopausal woman would lose anyway.

1,262 of the original 1,637 women entered the post-treatment follow-up study; the density figures come from a 2017 review of the published discontinuation studies

Measured in people

Source [07]Source [08]

Whether starting another bone drug straight afterwards makes a difference

It makes the difference. In the women who took nothing after stopping, density fell 10.0% at the spine (±5.4), 4.5% at the total hip (±3.6) and 4.2% at the neck of the thigh bone (±4.3). In the women who started a bone-preserving drug, the falls were 1.2% (±4.7), 0.8% (±3.1) and 0.6% (±2.7) — p<0.001 at every site. One caveat matters and is usually dropped: the untreated group had stopped either teriparatide or denosumab — a twice-yearly injection that works the opposite way round, by slowing bone breakdown — and the thigh-bone loss was much steeper in the denosumab stoppers (5.8% ±4.0) than in the teriparatide stoppers (0.8% ±2.6, p=0.008). So the drop is real, but the biggest numbers in this study are not all teriparatide's.

50 postmenopausal women followed a mean of 15.4 months (±3.5) after a randomised trial ended — 22 who took nothing afterwards and 28 who started a bone-preserving drug a mean of 3.8 months later

Measured in people

Source [15]

Back pain and quality of life outside a trial

Back pain, rated by patients on a 100 mm line, fell from 50.2 mm at the start to 27.8 mm at 24 months and 22.3 mm at 42 months — and it kept improving after the injections had stopped. A general quality-of-life score rose from 0.50 to 0.73 at 24 months and 0.78 at 42 months, with the biggest gains in pain and in being able to do ordinary daily things. Odds of a break coming to clinical attention were 47% lower in months 12 to 18 than in the first six months (p=0.013). About 98% of patients went on to another bone medicine after stopping — 51% to a bone tablet or infusion, 22% to denosumab, the twice-yearly injection that slows bone breakdown.

1,531 patients analysed of 1,611 enrolled across eight European countries, 90.7% women, mean age 70.3 years, median 23.6 months of treatment; 65.2% completed the full 42 months. This is an observational study run by the manufacturer, with no control group.

Measured in people

Source [18]

Bone cancer in people, after fifteen years of looking for it

Three cases where four were expected. A surveillance study ran from 1 January 2003 to 31 December 2016 through 30 US cancer registries, identifying 3,808 people with the rare bone cancer seen in the rats and interviewing 1,173 of them. Three said they had taken teriparatide before their diagnosis, and all three exposures were verified. The expected number, from the background rate, was 4.17 — giving a ratio of 0.72 (90% CI 0.20 to 1.86). The study was designed to be able to detect a threefold increase in risk, which would have meant one extra case per 156,000 people treated per year. Two separate US insurance-claims studies linked to cancer registries found 0 cases among 153,316 users and 3 among 379,283, against 3 versus 6 and 3 versus 9 in their comparison groups. A Nordic study across Denmark, Finland, Iceland, Norway and Sweden found 109 cases of the cancer and none with any record of teriparatide.

US cancer registry cases 2003–2016 with 1,173 interviews; two US claims cohorts totalling 532,599 teriparatide users against 2,679,577 comparators; 109 Nordic cases

Measured in people

Source [04]Source [22]

A once-weekly version, tested in China

A weekly injection of a larger amount raised lower-spine density 5.01% against 4.20% for weekly alendronate tablets over 48 weeks, a difference of 0.80 percentage points (p=0.025); hip density rose 3.27% against 1.67% (p<0.001). The safety trade is stark: 77.3% of the teriparatide group had a side effect judged drug-related against 39.9% on alendronate, and 5.0% stopped because of one against 0.8%. This weekly regimen is licensed in Japan and now studied in China. It is not the medicine sold in Europe or the United States, where teriparatide is a daily injection only.

493 Chinese postmenopausal women at 37 centres — 243 on weekly teriparatide, 250 on weekly alendronate — 48 weeks, open-label; 407 completed

Measured in people

Source [23]

How long people actually stay on it

The published answers do not agree, and the gap between them is the size of a whole clinical question. In US insurance claims, 67.1% of people had stopped teriparatide within 12 months and 87.9% within 24 — worse than denosumab, the twice-yearly injection, at 48.8% by 12 months, and about the same as the other injected bone drugs. In a Japanese claims database, 34.9% were still on it at 12 months, and 34.0% went on to no bone medicine at all. But in five Italian specialist osteoporosis centres, 86.85% were still taking it at 18 months. The likeliest explanation is not the drug but the setting: specialist clinics that supply, train and follow people up get very different numbers from an insurance database.

778 US patients starting teriparatide between 2008 and 2012, inside a cohort of 4,756 starting an injectable bone drug; 553 patients in a Japanese claims database 2005 to 2017; 475 patients at five Italian centres, 441 of whom completed 18 months

Studies in people disagree

Source [19]Source [20]Source [21]

Whether a second course works as well as the first

It does not. In the same people, a second 12-month course after a year off produced about half the gain at the spine and almost none at the hip: lower-spine density rose 12.5% (±1.5) in the first course and 5.2% (±0.8) in the retreatment; the neck of the thigh bone rose 2.8% (±1.3) and then 0.2% (±0.8). A separate study in people who stayed on alendronate throughout found the second course closer to the first, at 6.2% and then 4.7% at the spine. Nobody has measured whether a second course prevents fractures.

21 people — 12 men and 9 women, mean age 60 — given 24 months of teriparatide, then 12 months off, then 12 months of it again; and 27 people who completed a second course while continuing alendronate

One small study

Source [16]Source [17]

The product information lists pain in the limbs, nausea, dizziness and a drop in blood pressure on standing. In rat studies at high doses a type of bone cancer developed, which for a long time carried a boxed warning in the US and a two-year limit on treatment. After observational studies covering around 2.47 million patients, the FDA removed the warning on 16 November 2020 and replaced the absolute two-year limit with a risk-based judgement for people who remain at high fracture risk.

EffectWhat it feels likeHow often

A rare bone cancerSerious

This is the most important entry on the record and the one most often got wrong. Rats given near-lifetime daily injections developed it at up to 50% in the highest-dose group. That produced a boxed warning and an absolute two-year lifetime limit when the drug was approved in 2002 — and it stopped the pivotal trial early, at a median of 19 months, which is why nobody has a longer randomised dataset. Fifteen years of looking in people did not find it, and on 16 November 2020 the US regulator removed both the boxed warning and the absolute limit. What remains in the US label is a plain warning that the cancer occurred in rats, that cases have been reported since marketing, that observational studies have not found an increased risk, and that there is limited data beyond two years. Europe kept the 24-month cap.

Not found above the background rate in people. Three cases against 4.17 expected across fifteen years of US surveillance, a ratio of 0.72 (90% CI 0.20 to 1.86). Reported rarely since the drug went on sale: 26 mentions of it among 111,637 teriparatide reports on the US regulator's public file, which has no denominator and cannot be turned into a rate.

Source [04]Source [09]Source [10]

Too much calcium in the bloodSerious

Thirst, needing to pass water often, constipation, feeling sick, confusion. Anyone whose calcium is already high must not take the drug at all, and the US label warns that readings above 13 mg/dL have been reported since marketing. It also raises the risk of poisoning by digoxin, a heart tablet, because high calcium makes the heart more sensitive to it. High calcium is the 15th most reported term on the US regulator's public file for teriparatide, with 550 reports.

A reading above 2.76 mmol/L is uncommon — fewer than 1 in 100. Above 3.25 mmol/L is rare — fewer than 1 in 1,000. Transient rises in the hours after a dose are much commoner: at least one in 11% of women and 6% of men on the drug, against 2% of women and 0% of men on dummy injections, confirmed on repeat in 3% and 1%. In the head-to-head against romosozumab it was recorded in 10% of the teriparatide group.

Source [07]Source [09]Source [10]

Calcium deposits forming in small blood vessels in the skinSerious

Painful patches of skin that can break down into ulcers that heal badly. The US label names the people it happens to: those with an autoimmune disease, kidney failure, or who are taking warfarin or steroid tablets. It instructs that the drug be stopped if this appears or if existing calcium deposits in the skin get worse. It is not in the European table.

No rate published. It appears in the US label as something reported since the drug went on sale, not as something counted in a trial.

Source [09]

A whole-body allergic reactionSerious

Sudden difficulty breathing, swelling of the mouth or face, a rash over the body, chest pain, swelling of the ankles. The US label lists swelling under the skin and anaphylaxis among the reactions reported since marketing, and hypersensitivity to teriparatide is the only outright bar on the US label.

Rare — fewer than 1 in 1,000. The European table also carries a separate rare entry for possible allergic events soon after injection.

Source [07]Source [09]

Kidney failure or worsening kidney functionSerious

The drug is barred outright in Europe for anyone with severe kidney impairment and used with caution in moderate impairment. On kidney stones the trials found no difference from dummy injections, but the drug was never tested in anyone who had stones at the time, so both labels advise caution in anyone with active or recent stones. In the US trials, no clinically important kidney effects were seen on any measure.

Rare — fewer than 1 in 1,000 in the European table. Kidney stones are listed separately as uncommon, fewer than 1 in 100.

Source [07]Source [09]

A cramp or pain in the back within minutes of injectingSerious

It arrives fast, it can be severe, and it eases on its own. The reason this is separated out from ordinary back pain is that footnote — regulators rarely annotate an uncommon entry, and this one is there because the pattern is distinctive enough to be recognised. Back pain is the eighth most reported term for teriparatide on the US regulator's public file, with 5,919 reports.

Back cramp and back pain are listed as uncommon — fewer than 1 in 100 — but the European table attaches a footnote of its own: serious cases have been reported within minutes of the injection.

Source [07]Source [10]

Pain in an arm or leg

The defining nuisance of this drug, and the hardest to interpret, because everyone taking it has painful bones already. It is the third most reported term on the US regulator's public file, with 8,349 reports. The European regulator lists it among the reactions that were at least 1 percentage point commoner than on dummy injections, so at least part of it is the drug.

Very common — at least 1 in 10, the only entry in the European table at that frequency. Joint pain 10.1% against 8.4% on dummy injections; leg cramps 2.6% against 1.3%.

Source [07]Source [09]Source [10]

Feeling sick

Named by the European regulator as one of the four commonest reactions, alongside limb pain, headache and dizziness, and one of only six listed as at least 1 percentage point commoner than on dummy injections. It is the single most reported term for teriparatide on the US regulator's public file, with 8,982 reports. Vomiting is listed as common too.

Common. 8.5% of 691 people on the drug against 6.7% of 691 on dummy injections. Much higher in people also on long-term steroid tablets: 14% against 7% on a daily bone tablet.

Source [07]Source [09]

Dizziness and fainting

Mostly this is the blood pressure dropping when standing, in the four hours after a dose. It settles by itself. It carries more weight in this population than the percentages suggest, because a faint in someone with fragile bones is a fall, and a fall is the thing the drug is there to prevent the consequences of. Falls are the fifth most reported term on the US regulator's public file for teriparatide, with 7,893 reports — though that file cannot separate falls caused by the drug from falls that were the reason the drug was prescribed.

Dizziness 8.0% against 5.4% on dummy injections; a spinning sensation 3.8% against 2.7%; fainting 2.6% against 1.4%.

Source [09]Source [10]

Low mood

Listed by the European regulator as one of the six reactions at least 1 percentage point commoner than on dummy injections, which is why it is here rather than being written off as the mood of someone with painful spinal fractures. In the trial in people on long-term steroid tablets, anxiety was reported by 4% against 1% and sleeplessness by 5% against 1%.

Common. 4.1% of people on the drug against 2.7% on dummy injections. Trouble sleeping 4.3% against 3.6%.

Source [07]Source [09]

Reactions where the needle goes in

The commonest practical complaint of a daily injection, and it accumulates: there are four separate injection-site terms in the top fifteen on the US regulator's public file for teriparatide — redness (5,052 reports), pain (4,815), bruising (4,768) and bleeding (4,497). The injection goes into the thigh or the belly, and the site is meant to be varied.

Common — mild and short-lived pain, swelling, redness, bruising, itching and minor bleeding. Redness and other injection-site reactions as named events are uncommon.

Source [07]Source [10]

Uric acid rising in the blood

This is worth knowing about only because of what it did not cause. Raised uric acid is what produces gout, and the European regulator states explicitly that the rise did not produce any increase in gout, joint pain or kidney stones. It is an abnormal number on a blood test that went nowhere.

2.8% of people on the drug had a level above the upper limit of normal against 0.7% on dummy injections. The US label rounds this to 3% against 1%.

Source [07]Source [09]

The body making antibodies against the drug

Antibodies generally appeared after 12 months of treatment and faded once the drug was stopped. Both regulators state there was no sign of allergic reactions, no effect on blood calcium and no effect on how much bone density improved. This is an immune response that appears to do nothing.

Detected in 2.8% of women in the European figures and 3% — 15 of 541 — in the US figures.

Source [07]Source [09]

Everything else, taken together

This row exists because the individual percentages above are easy to read as an alarming list, and the totals say something the list does not. On every summary measure the trials recorded, teriparatide was indistinguishable from a dummy injection, or slightly better. In people on long-term steroid tablets the picture is less comfortable: 21% had a serious event against 18% on a daily bone tablet, and 15% stopped early against 12%.

82.8% of people on teriparatide reported at least one adverse event of some kind — against 84.5% of the people on dummy injections. Serious events happened to 16% on the drug against 19% on dummy injections. 7% stopped early because of a side effect against 6%. Death from any cause: 1% in each group.

Source [07]Source [09]

These are the amounts the studies below gave their participants, and they are here as facts about those studies. They are not a recommendation, not a starting point and not a range to pick from. What a person should take, if anything, is a question for a doctor who knows them.

The Fracture Prevention Trial, the pivotal study, in 1,637 postmenopausal women who had already broken a bone in the spine

20 or 40 micrograms once a day, injected under the skin, against a dummy injection; everyone was also given 1,000 mg of calcium and at least 400 IU of vitamin D a day. Only the 20-microgram amount was later approved.

Planned for up to 24 months and stopped early; median treatment exposure 19 months, median observation 21 months. It was stopped because of the bone cancer found in rats.

Source [01]Source [07]

VERO, the head-to-head against risedronate, in 1,360 postmenopausal women with severe osteoporosis

20 micrograms once a day injected under the skin plus a weekly dummy tablet, against 35 mg of risedronate once a week plus a daily dummy injection

24 months

Source [12]

The trial in 428 men and women on long-term steroid tablets, against alendronate

20 micrograms once a day injected under the skin, against 10 mg of alendronate a day; everyone was also given 1,000 mg of calcium and 800 IU of vitamin D a day

36 months in total, with an 18-month main phase

Source [07]

The trial in 437 men with osteoporosis, either from low testosterone or of no known cause

20 micrograms once a day injected under the skin, given to 151 of the men, against a dummy injection

Median treatment exposure about 10 months

Source [07]Source [09]

The open-label study in 503 postmenopausal women with severe osteoporosis who had broken a bone in the previous three years, 83% of whom had already been on another bone treatment

20 micrograms once a day, injected under the skin

Up to 24 months

Source [07]

STRUCTURE, the head-to-head against romosozumab in 436 women coming off long-term bone tablets

20 micrograms of teriparatide once a day injected under the skin, against 210 mg of romosozumab injected once a month

12 months

Source [13]

ExFOS, the European observational study of ordinary practice in 1,531 patients across eight countries

20 micrograms once a day injected under the skin, as prescribed by the patients' own doctors rather than assigned by a trial

Median 23.6 months on the drug, then 18 months of follow-up after stopping

Source [18]

The retreatment study in 21 people — 12 men and 9 women — that tested whether a second course works

20 micrograms once a day, injected under the skin, in both courses

24 months, then 12 months with no treatment, then 12 months of it again

Source [16]

The Chinese phase 3 study of a once-weekly regimen — a different schedule of the same molecule, licensed in Japan and not sold in Europe or the United States

56.5 micrograms once a week injected under the skin, against 70 mg of alendronate once a week by mouth

48 weeks

Source [23]

What people report

• Whether it prevents broken hips — the pivotal trial saw 0.2% against 0.7% on dummy injections, far too few events to answer, and the European regulator states the reduction has not been demonstrated
• Whether taking it for longer than two years is safe — the pivotal trial was stopped early at a median of 19 months because of the rat finding, so no randomised data beyond 24 months exists in any population, and the US label says exactly that
• Whether it prevents fractures in men — the only trial in men ran a median of about ten months and measured bone density, not breaks
• Whether a second course prevents any fractures — two small studies measured only bone density, and one found the density response roughly halved after a year off the drug
• Why the bone-building effect fades after 6 to 12 months — a 2026 review sets out five competing explanations, from running out of bone-building precursor cells to the bone sensing it no longer needs more, and concludes that most of the evidence is indirect and comes from animals
• Whether the small fall in density at the shaft of the forearm bone matters — it has been measured repeatedly and never linked to a fracture either way
• How often the severe back cramp within minutes of injecting actually happens — the European regulator flags serious cases in a footnote but attaches no rate to it, and nobody has counted them
• What causes it in the people it does happen to, and whether it predicts anything — no published study has followed up the people who report it
• Whether the fridge requirement, the daily needle or the cost is what makes people stop — the published persistence figures range from 34.9% still taking it at 12 months to 86.85% at 18, and none of the studies asked anybody why they left
• Whether it is safe in pregnancy — Europe bars it outright, the US label states there are no human data at all, and the animal work found skeletal variations in mice at 60 times the human dose
• What it does in liver disease — the European product information states there are no data in impaired liver function, which is why it is used with caution rather than barred
• Whether it works in people who have been on bone tablets for years — the one head-to-head that looked found hip density falling on teriparatide in exactly that group, and no trial has tested whether that translates into more fractures
• Whether the once-weekly regimen licensed in Japan prevents fractures — the Chinese trial published in 2026 measured bone density over 48 weeks, and its rate of drug-related side effects was nearly twice the comparator's
• Whether stopping without starting another bone drug leads to more broken bones, rather than just lower scan readings — the cleanest study of stopping measured density in 50 women and was never designed to count fractures

Will it give me bone cancer?

This was investigated for fifteen years and the answer is that it has not been found in people. Rats given daily injections for most of their lives developed a rare bone cancer, at up to 50% in the highest-dose group, and that produced a boxed warning and a strict two-year lifetime limit when the drug was approved in 2002. From 2003 to 2016 a surveillance study worked through 30 US cancer registries, found 3,808 people with that cancer and interviewed 1,173 of them: three had taken teriparatide, where 4.17 were expected from the background rate. Two insurance-claims studies linked to cancer registries found 0 cases among 153,316 users and 3 among 379,283. A Nordic study found 109 cases of the cancer and none with any record of the drug. On 16 November 2020 the US regulator removed the boxed warning and the absolute limit. What remains is an ordinary warning: the cancer occurred in rats, cases have been reported since marketing, observational studies have not found an increased risk, and there is limited data beyond two years.

Source [04]Source [09]Source [22]

Why does it have to be every day?

Because the effect depends entirely on the shape of the dose, not just the amount. Parathyroid hormone kept high all the time takes bone apart — that is what happens in people whose parathyroid glands are overactive. The same hormone delivered as a short daily spike does the opposite: the cells that build bone get ahead of the cells that break it down and new bone is laid on. Teriparatide clears the body fast enough to make that spike, with a half-life of about an hour after injection under the skin, and blood calcium is back to normal within 16 to 24 hours. A long-acting version would not be a more convenient teriparatide; it would be a drug that takes bone away. A once-weekly regimen at a larger amount does exist and is licensed in Japan, but it is a different product and is not sold in Europe or the United States.

Source [07]Source [08]

What happens when the two years are up?

The bone you gained starts coming off unless something else is started. In the women who stopped and took nothing, spine density fell 10.0% and total hip density 4.5% over about fifteen months. In the women who started a bone-preserving drug promptly, the same measurements fell 1.2% and 0.8%. A review of the field puts the spine loss at 2.2% to 4.4% in the first year off the drug, against the 0.5% to 1.0% a year an untreated postmenopausal woman loses anyway. The fracture protection lasts longer than the density does — over a median of 18 months after the pivotal trial there were still 41% fewer women with a new spinal break — but other treatments were allowed in that period, so that is not a picture of stopping and taking nothing. In practice most people are moved onto a bone tablet, a yearly infusion or denosumab: in the European observational study about 98% went onto something, 51% to one of the common bone tablets or infusions and 22% to denosumab. In a Japanese claims database, 34.0% went onto nothing.

Source [07]Source [15]Source [18]Source [20]

Why can I only have two years of it in Europe when Americans can have more?

Because the two regulators read the same evidence differently and one of them acted on it. Both capped treatment at two years in 2002 because of the rat cancer. In November 2020 the US regulator, having seen the surveillance and claims studies, removed the absolute limit and replaced it with a judgement: more than two years should only be considered if a person remains at, or has returned to, high risk of fracture. The current European product information still says the maximum total duration is 24 months and that the course must not be repeated in a patient's lifetime, and it gives its reason plainly — rats developed the cancer with long-term dosing, and until further clinical data are available the 24-month limit should not be exceeded. The European text was last revised as of a page update on 28 January 2026, so this is the current position and not an oversight.

Source [02]Source [07]Source [09]

Is it actually better than the ordinary bone tablets?

For breaks in the spine, in people who already have severe osteoporosis, yes and by a clear margin. Tested directly against risedronate in 1,360 women over two years, new spinal breaks happened to 5.4% on teriparatide against 12.0% on the tablet, and breaks that came to clinical attention to 4.8% against 9.8%. Against alendronate in people on long-term steroid tablets, new spinal breaks at three years were 1.7% against 7.7%. But the advantage does not extend everywhere. Breaks outside the spine were 4.0% against 6.1% in the head-to-head — a difference that could have been chance. Breaks elsewhere in the steroid trial were identical, 7.5% against 7.0%. And against romosozumab, a monthly injection, teriparatide lost outright at the hip in women coming off long-term tablets: hip density rose 2.6% on romosozumab and fell 0.6% on teriparatide.

Source [07]Source [12]Source [13]

Will it stop me breaking a hip?

Nobody knows, and the European regulator says so on the label rather than letting it be assumed. In the pivotal trial 0.2% of women on the drug broke a hip against 0.7% on dummy injections — a difference of the right shape, built on a handful of events, in a trial stopped early. The product information states that a significant reduction in hip fractures has not been demonstrated, and the indication is worded around that. Hip density does rise, but by 2.6% against the spine's 9.7%. A 2025 analysis of 17 studies found abaloparatide, a close relative, did better than teriparatide specifically on hip fractures.

Source [07]Source [09]Source [11]

Will it help the back pain I already have?

The evidence is about new or worsening back pain, not about pain you already have, and on that it is consistent. Pooling five randomised trials, new or worsening back pain was about a third less likely on teriparatide than on whatever it was compared with — a relative risk of 0.66 for any back pain, 0.60 for moderate or severe and 0.44 for severe. In ordinary European practice, patients rated their back pain at 50.2 mm on a 100 mm line at the start, 27.8 mm at 24 months and 22.3 mm at 42 months, and it carried on improving after the injections stopped. That observational study had no control group, and spinal fractures hurt most while they are healing, so some of that improvement would have happened anyway.

Source [14]Source [18]

Does it work for men?

It raises bone density in men and it has never been shown to prevent a fracture in them. In 437 men followed for a median of about ten months, lower-spine density was 5% higher and total hip 1% higher than on dummy injections, and the rise at the spine was already significant at three months. The regulator states that no significant effect on fracture rates was demonstrated — the trial was not built to answer that. The European indication for men is worded as treatment of osteoporosis in men at increased risk of fracture, not as fracture prevention, and that wording is doing real work.

Source [07]Source [09]

Can I have a second course later?

In Europe, no — the product information says the 24-month course must not be repeated over a patient's lifetime. In the United States the absolute bar was lifted in November 2020, and more than two years may be considered if someone remains at or returns to high fracture risk. What the evidence shows is that a repeat works less well. In 21 people given a second twelve-month course after a year off, lower-spine density rose 5.2% against 12.5% the first time, and the neck of the thigh bone rose 0.2% against 2.8%. In people who stayed on alendronate throughout, the second course came closer to the first — 4.7% against 6.2% at the spine. No study has measured whether a second course prevents fractures.

Source [07]Source [09]Source [16]

Is it a difficult drug to tolerate?

On the trial totals, no — and this is the number most likely to surprise someone reading the side-effect list. 82.8% of people on teriparatide reported at least one adverse event of some kind, against 84.5% of the people on dummy injections. Serious events happened to 16% on the drug and 19% on the dummy. 7% stopped early because of a side effect, against 6%. Only six things were at least 1 percentage point commoner than on a dummy injection: a spinning sensation, feeling sick, pain in a limb, dizziness, low mood and breathlessness. In people also taking long-term steroid tablets the balance is worse — 15% stopped early against 12% on a daily bone tablet, and nausea was reported by 14% against 7%. Whether people stay on it outside a trial is a separate question with a much worse answer.

Source [07]Source [09]

Has anything changed recently?

Two things. The first generic version was approved in the United States on 15 December 2025 — Amphastar's teriparatide injection, judged equivalent to Forteo, in a market worth about $585 million in the twelve months to 30 September 2025. Copies have been available in Europe for longer: Movymia and Terrosa were approved in January 2017 as biosimilars — near-identical versions of a medicine grown in living cells, which cannot be copied exactly the way a chemical tablet can — followed by Livogiva, Sondelbay and Kauliv. The UK charity now lists five brands. The second is what has not changed: the European 24-month cap and lifetime no-repeat rule are still in the current product information, more than five years after the US dropped its equivalent.

Source [05]Source [24]Source [25]

Each letter represents one amino acid.

1. [01]Effect of parathyroid hormone (1-34) on fractures and bone mineral density in postmenopausal women with osteoporosis, NEJM (2001)
2. [02]EMA – Forsteo (teriparatide), EPAR: approved 10 June 2003 (2003)
3. [03]UniProt P01270 – Parathyroid hormone, Homo sapiens (moget PTH = position 32–115)
4. [04]Teriparatide and Osteosarcoma Risk: History, Science, Elimination of Boxed Warning, and Other Label Updates, JBMR Plus (2022)
5. [05]EMA – Movymia (teriparatide), biosimilar to Forsteo, approved 11 January 2017 (2017)
6. [06]WADA International Standard Prohibited List 2026 (teriparatide and parathyroid hormone do not appear on the list) (2026)
7. [07]European Medicines Agency — Forsteo (teriparatide) product information, section 5.1 Pharmacodynamic effects and section 5.2 Distribution
8. [08]Eastell R, Walsh JS. Anabolic treatment for osteoporosis: teriparatide. Clinical Cases in Mineral and Bone Metabolism (2017)
9. [09]DailyMed / Lilly — FORTEO (teriparatide) injection, US prescribing information, Table 3 and Clinical Studies 14.1
10. [10]openFDA drug adverse event counts for teriparatide, reaction terms by frequency (data last updated 28 April 2026) (2026)
11. [11]PTH1 receptor agonists for fracture risk: a systematic review and network meta-analysis. Osteoporosis International (2025)
12. [12]Kendler DL et al. Effects of teriparatide and risedronate on new fractures in post-menopausal women with severe osteoporosis (VERO): a multicentre, double-blind, double-dummy, randomised controlled trial. Lancet (2018)
13. [13]Langdahl BL et al. Romosozumab (sclerostin monoclonal antibody) versus teriparatide in postmenopausal women with osteoporosis transitioning from oral bisphosphonate therapy (STRUCTURE): a randomised, open-label, phase 3 trial. Lancet (2017)
14. [14]Nevitt MC et al. Reduced risk of back pain following teriparatide treatment: a meta-analysis. Osteoporosis International (2005)
15. [15]Leder BZ et al. Importance of prompt antiresorptive therapy in postmenopausal women discontinuing teriparatide or denosumab (DATA-Follow-up). Bone (2017)
16. [16]Finkelstein JS et al. Effects of teriparatide retreatment in osteoporotic men and women. J Clin Endocrinol Metab (2009)
17. [17]Cosman F et al. Retreatment with teriparatide one year after the first teriparatide course in patients on continued long-term alendronate. J Bone Miner Res (2009)
18. [18]Napoli N et al. Effects of teriparatide in patients with osteoporosis in clinical practice: 42-month results during and after discontinuation of treatment from the European Extended Forsteo Observational Study (ExFOS). Calcified Tissue International (2018)
19. [19]Modi A et al. Frequency of discontinuation of injectable osteoporosis therapies in US patients over 2 years. Osteoporosis International (2017)
20. [20]Persistence of and switches from teriparatide treatment among women and men with osteoporosis in the real world: a claims database analysis. Archives of Osteoporosis (2018)
21. [21]Evaluation of persistence and adherence to teriparatide treatment in patients affected by severe osteoporosis (PATT): a multicenter observational real life study. Clinical Cases in Mineral and Bone Metabolism (2013)
22. [22]Gilsenan A et al. Teriparatide did not increase adult osteosarcoma incidence in a 15-year US postmarketing surveillance study. J Bone Miner Res (2021)
23. [23]Efficacy of once-weekly teriparatide versus alendronate in Chinese postmenopausal osteoporosis: a randomised, open-label, active-controlled, 48-week, multicentre phase III study. Journal of Orthopaedic Translation (2026)
24. [24]Amphastar announces FDA approval for teriparatide injection, 15 December 2025 (2025)
25. [25]Royal Osteoporosis Society — teriparatide, brands available in the UK