Teriparatide (Forteo): Denser Bones, Not a Taller You
A daily PTH 1-34 injection that measurably strengthens the spine in osteoporosis. The trials measured fractures and bone density, not height gain, and adult growth plates have already fused.
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How It Works
Teriparatide is recombinant human parathyroid hormone 1-34, a 34-amino-acid fragment given as a daily self-injection. Given intermittently, PTH acts as an anabolic (bone-building) agent and is approved for women and men at high fracture risk (PMID 14713402).
Bones grow longer only at the growth plate. The growth plate narrows through childhood and disappears at the end of puberty, replaced by bone, and longitudinal growth stops (PMID 21540578). Teriparatide acts on bone mass and strength; an adult skeleton has no growth plate left for it to lengthen.
In developing bone, PTHrP acts on PTH/PTHrP receptors on growth-plate chondrocytes and keeps them proliferating (PMID 16831900). That biology belongs to growing cartilage in a developing skeleton. It does not show that a PTH injection lengthens adult bones, and no study we found tested that.
In the Fracture Prevention Trial, worsening spinal fracture burden was associated with greater height loss and back pain. Teriparatide 20 µg cut the share of patients whose spinal fracture severity score rose by more than 1, 2 or 3 grades by 85%, 80% and 80% (PMID 15961357). The best case here is less height lost to spinal fractures, not height gained.
What the Data Shows
Key Takeaways
- Teriparatide 20 µg/day reduced new vertebral fractures (5% vs 14% on placebo) and nonvertebral fragility fractures in postmenopausal women with prior vertebral fractures (PMID 11346808).
- It raised lumbar-spine bone density by 9 percentage points more than placebo at 20 µg (PMID 11346808).
- In severe osteoporosis it beat risedronate on new vertebral fractures: 5.4% vs 12.0% over 24 months (PMID 29129436).
- The viral "-86% spinal fractures" figure is the abaloparatide (Tymlos) result from the ACTIVE trial, a different PTHrP-analog drug (PMID 27612281).
- Adult long bones stop lengthening once the growth plate is replaced by bone at the end of puberty (PMID 21540578).
- Large registry studies found osteosarcoma rates in teriparatide users within the expected background range, and the US boxed warning was removed in 2020 (PMID 35318162, PMID 36111201).
- We found no trial measuring height gain in adults on teriparatide; the pivotal trials measured fractures and bone density (PMID 11346808, PMID 29129436).
- Whether it restores height already lost to spinal fractures has not been shown. The evidence covers slowing further fracture burden, which is linked to height loss (PMID 15961357).
- We could not trace the thread's "+11.2% lumbar BMD" figure to a source. The teriparatide pivotal abstract reports lumbar-spine density 9 percentage points above placebo at 20 µg (PMID 11346808); we did not confirm the 11.2% figure for either drug.
- Osteosarcoma estimates in humans remain imprecise because the cancer is so rare (PMID 35318162).
- Long-term data in healthy young adults without osteoporosis do not exist; the trials enrolled postmenopausal women at high fracture risk (PMID 11346808, PMID 29129436).
Frequently Asked Questions
Can teriparatide make you taller?
No evidence says so. Adult bones lengthen only at growth plates, which are replaced by bone at the end of puberty (PMID 21540578). Teriparatide trials measured fractures and bone density, not height gain (PMID 11346808). Its documented height-related benefit is indirect: fewer worsening spinal fractures, which are linked to height loss (PMID 15961357).
Where does the "86% fewer spinal fractures" number come from?
That figure comes from the ACTIVE trial of abaloparatide (Tymlos), a different drug that activates the same PTH1 receptor: an 86% reduction in new vertebral fractures vs placebo over 18 months (PMID 27612281). Teriparatide's own pivotal trial showed a 65% reduction at 20 µg (relative risk 0.35, PMID 11346808).
Is teriparatide safe for teenagers who are still growing?
Clinical reviews state that children and young adults with open epiphyses are at higher risk for osteosarcoma and should not be given PTH (PMID 14713402). In children with hypoparathyroidism, long-term PTH 1-34 used as hormone replacement kept height velocity in the normal range rather than boosting it (PMID 30470382).
Does teriparatide cause bone cancer?
High doses caused osteosarcoma in rats treated for near their whole lifetime, which led to the original boxed warning. Large US registry studies later found osteosarcoma rates in teriparatide users within the expected background range, and the label was updated in 2020 to remove the boxed warning (PMID 36111201, PMID 35318162).
Can teriparatide restore height lost to osteoporosis?
That has not been shown. In the Fracture Prevention Trial, increasing spinal fracture burden was associated with greater height loss, and teriparatide sharply reduced the share of patients whose fracture burden increased (PMID 15961357). That points to slowing future height loss, not regaining height.
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Teriparatide is a prescription osteoporosis drug. Decisions about it belong with a qualified clinician.