Teriparatide is the first 34 amino acids of human parathyroid hormone, made by recombinant DNA. That fragment, often written PTH(1-34), keeps the receptor-binding business end of the full hormone. The FDA approved it in November 2002 under the brand Forteo (Eli Lilly), and it was the first anabolic, or bone-building, drug cleared for osteoporosis. A second brand, Bonsity, and several biosimilars followed. You may also see the development codes LY 333334 or ZT-034, or the CAS number 52232-67-4.
Most osteoporosis drugs, like bisphosphonates, are antiresorptive: they slow the cells that break bone down. Teriparatide works the other way. It tells the body to make new bone.
How it works
The mechanism turns on a quirk of how the body reads PTH. Continuous high PTH exposure, as in hyperparathyroidism, drives bone loss. But a brief, once-daily spike does the opposite and stimulates bone formation. Teriparatide is given as a daily subcutaneous injection (20 mcg) precisely to recreate that intermittent pattern.
At the cellular level it binds the PTH type 1 receptor on osteoblasts, the bone-forming cells. According to StatPearls, that signal upregulates growth factors such as IGF-1, suppresses sclerostin (a brake on the bone-building Wnt pathway), and helps osteoblasts live longer instead of dying off. Net result: more bone gets laid down than removed, at least early in treatment.
What the research shows
The evidence here is unusually solid for a peptide. The pivotal study was the Fracture Prevention Trial, published by Neer and colleagues in the *New England Journal of Medicine* (2001). It randomized 1,637 postmenopausal women with prior vertebral fractures to teriparatide or placebo. Over a median of 21 months, the 20-mcg dose cut new vertebral fractures by 65 percent and nonvertebral fragility fractures by 53 percent versus placebo, while raising lumbar spine bone density by roughly 10 percent. A 40-mcg dose added density but not fracture protection, and caused more side effects, which is why 20 mcg became the approved dose.
Later trials extended the indication to men with osteoporosis and to glucocorticoid-induced osteoporosis, where teriparatide outperformed the bisphosphonate alendronate on bone density and vertebral fractures (Saag et al., *NEJM* 2007).
Regulatory and safety notes
Teriparatide is a prescription drug, not a research chemical, approved by the FDA and EMA for specific high-fracture-risk patients. Early rat studies showed osteosarcoma at high lifetime doses, which produced a boxed warning and a two-year treatment cap. In 2020 the FDA removed both, citing a 15-year postmarketing surveillance study that found no increased osteosarcoma signal in people (review in *JBMR Plus*, 2022). It is still avoided in patients with conditions that predispose to bone tumors.
For athletes: teriparatide is a peptide hormone with anabolic action on bone. WADA's Prohibited List covers peptide hormones and substances with similar biological effects, so anyone in tested sport should confirm current status through Global DRO rather than assume.
The buyer angle: identity and purity
Because teriparatide is a real approved injectable, the pharmaceutical product comes with a known sequence, defined strength, and manufacturer quality control. Material sold through gray-market "research" channels does not carry those guarantees. For a 34-residue peptide, the things worth checking on a certificate of analysis are identity (is the sequence actually PTH 1-34, confirmed by mass spec), purity (HPLC percentage, and what the impurities are), and whether the COA is batch-specific and traceable to a named lab rather than a generic PDF. peptideone aggregates third-party COA and vendor-rating data so these claims can be compared instead of taken on faith.
Nothing here is medical or dosing advice. Research-grade peptides are sold for laboratory use only and are not for human consumption; the approved drug is a separate, prescription-only product.