A 34-amino-acid peptide identical to the N-terminal active fragment of human parathyroid hormone (PTH 1-34, CAS 52232-67-4). It binds the same receptors as endogenous PTH, and its effect on bone depends on the pattern of exposure: intermittent exposure stimulates bone formation by favoring osteoblast over osteoclast activity, while continuous PTH excess can favor resorption. FDA-approved for osteoporosis as Forteo and as generic teriparatide injection.
For research purposes only. Not medical advice.
Teriparatide is the 1-34 fragment of human parathyroid hormone (PTH). Its receptor is the PTH type 1 receptor (PTH1R), which also mediates the actions of the hormone's second endogenous ligand, PTH-related peptide (PTHrP). The Forteo label states that teriparatide and the 34 N-terminal amino acids of PTH bind these receptors with the same affinity and have the same physiological actions on bone and kidney.
The Hormonal category covers why exposure timing decides its effect on bone. The label describes the anabolic side in humans as an increase in skeletal mass, in markers of both bone formation and resorption, and in bone strength.
Abaloparatide, approved in 2017 as Tymlos, is the closest mechanistic comparison. Its label describes a synthetic 34-amino-acid analog of PTHrP(1-34) that acts as an agonist at PTH1R and shares 41% homology with hPTH(1-34). In cell assays published in 2016 by its developer, Radius Health, abaloparatide bound the receptor's RG conformation more selectively than PTH(1-34) did and produced shorter-lived cAMP responses. It is an in vitro finding, not a clinical comparison.
The Fracture Prevention Trial, the placebo-controlled study in Eli Lilly's Forteo application, was reported by Neer and colleagues in the New England Journal of Medicine in 2001. It randomized 1,637 postmenopausal women with prior vertebral fractures to one of two teriparatide dose arms or placebo, with a median observation of 21 months. Comparing spine radiographs taken at baseline and at study end, new vertebral fractures occurred in 14% of women on placebo and in 5% and 4% of the two teriparatide arms, relative risks of 0.35 and 0.31. New nonvertebral fragility fractures occurred in 6% on placebo and 3% in each teriparatide arm. The Forteo label reports only the arm matching the approved product, counting 444 of its 541 women, and gives 5.0% against 14.3%, a 65% relative reduction.
VERO, a Lilly-funded double-blind trial reported by Kendler and colleagues in The Lancet in 2018, compared teriparatide with oral risedronate in 1,360 postmenopausal women with severe osteoporosis over 24 months, with new radiographic vertebral fractures as the primary outcome. New vertebral fractures occurred in 5.4% of the teriparatide group and 12.0% of the risedronate group (risk ratio 0.44). The difference in nonvertebral fragility fractures, 4.0% against 6.1%, was not statistically significant.
FDA approved Forteo, listed in its approval package as teriparatide (rDNA origin), on November 26, 2002 (NDA 021318). The current label says it is made in a strain of Escherichia coli modified by recombinant DNA technology.
The 2002 label opened with a boxed warning: in male and female rats, teriparatide increased the incidence of osteosarcoma, a malignant bone tumor, and the label called the finding's relevance to humans uncertain. On November 16, 2020, FDA approved a Lilly supplement whose letter lists "Removal of the Boxed Warning regarding osteosarcoma" and a revision reflecting long-term osteosarcoma surveillance studies. The current label keeps osteosarcoma as a warning and says an increased risk has not been observed in observational studies in humans. Its two US claims-database studies found three cases among 379,283 Forteo users and none among 153,316, and the label cautions that those data sources cannot fully control for confounders.
As of October 22, 2026, Drugs@FDA lists five other teriparatide injections in prescription status. Two are NDAs filed under the 505(b)(2) pathway: Bonsity (NDA 211939, October 2019) and a teriparatide injection approved under NDA 218771 on June 4, 2024, which relies on FDA's findings for Forteo. FDA's review of NDA 218771 says it uses the chemistry and manufacturing approved under NDA 211939, a teriparatide made in Pseudomonas fluorescens. The other three are ANDAs, the first two approved November 16, 2023.
FDA's regulations define a protein as an amino acid polymer greater than 40 amino acids in size (21 CFR 600.3(h)(6)). At 34, teriparatide falls under that line, and Forteo is still listed in Drugs@FDA as an NDA. FDA's May 2021 guidance on synthetic peptide ANDAs named teriparatide as one of five rDNA-origin products, teduglutide among them, and called all five peptides rather than proteins. FDA withdrew that guidance on July 28, 2026, the day it published revised draft product-specific guidances for generic peptides, two of them for teriparatide. The July 2026 guidance analysis covers that lane.
Because teriparatide holds current approvals, the 503A bulks-list and Category 2 process is not where its status is decided. It appears in neither table of FDA's Category 2 page (content current as of April 22, 2026), nor in the 503A nominations categories list updated May 14, 2026 or the 503B list updated March 21, 2025.
The labels call it teriparatide and describe it as a recombinant human parathyroid hormone analog (PTH 1-34). The 2001 trial report uses parathyroid hormone (1-34), Lilly-authored papers use rhPTH(1-34), and animal studies from 1999 to 2001 identify recombinant human PTH(1-34) by the code LY333334.
Forteo, from Eli Lilly, was approved on November 26, 2002 under NDA 021318. As of October 22, 2026, Drugs@FDA also lists two other NDAs filed under the 505(b)(2) pathway, Bonsity (NDA 211939) and a teriparatide injection under NDA 218771, plus three ANDAs for generic teriparatide injection. These approvals cover the licensed injection products, not research-grade powder.
No. Forteo was approved in 2002 with a boxed warning because teriparatide increased the incidence of osteosarcoma, a malignant bone tumor, in rats. FDA approved a supplement removing the boxed warning on November 16, 2020. The current label keeps osteosarcoma as a warning based on the rat finding and states that an increased risk has not been observed in observational studies in humans.
The trial, reported by Neer and colleagues in the New England Journal of Medicine in 2001, randomized 1,637 postmenopausal women with prior vertebral fractures to two teriparatide dose arms or placebo, with a median observation of 21 months. Comparing spine radiographs at baseline and study end, new vertebral fractures occurred in 14% of women on placebo and in 5% and 4% of the two teriparatide arms, relative risks of 0.35 and 0.31.
Both are 34-amino-acid peptides that act at the PTH type 1 receptor. Teriparatide has the sequence of human parathyroid hormone 1-34. Abaloparatide, approved as Tymlos in 2017, is a synthetic analog of PTH-related peptide 1-34 that its label says shares 41% homology with human PTH 1-34. In 2016 cell assays by its developer, abaloparatide bound one receptor conformation more selectively than PTH 1-34 and gave shorter cAMP signals, an in vitro difference rather than a clinical comparison.
No. FDA defines a protein as an amino acid polymer of more than 40 amino acids, and teriparatide has 34, so it is regulated as a drug even though Forteo is made by recombinant DNA technology. Forteo is approved under a new drug application, NDA 021318, rather than a biologics license.
Teriparatide's CAS Registry Number is 52232-67-4.
