Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library

Parathyroid hormone (PTH 1-84, Natpara): what the evidence says

Name: Parathyroid hormone (PTH 1-84, Natpara)
Published: 2026-10-27

At a glance

What it is: the full 84-amino-acid human parathyroid hormone, made recombinantly. It was approved as Natpara for hypoparathyroidism, but Takeda stopped making it at the end of 2024. ^{R1, R2, R3}

What the evidence says: Human in REPLACE (134 adults), 53% met the main goal (cutting calcium and active vitamin D by half while keeping calcium normal) vs 2% with placebo. ^R4 A later 1-year open-label study (22 patients) kept calcium in range in most patients. ^R5

Biggest risks: carried a boxed warning for osteosarcoma (bone cancer, seen in rats) and was available only through a restricted program (REMS). ^R3

Rating


Human Human evidence	Moderate: one phase 3 RCT (n = 134) plus a small open-label study ^{R4, R5}
Animal Animal / lab evidence	Not reviewed
Regulatory	FDA-licensed (BLA125511) but discontinued by the maker ^{R1, R2} · not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page ^{R6, R7, R8} · not named by WADA ^R9
Established human dose	Yes, former label dose (see Study details)

Evidence verdict: Hypoparathyroidism: Moderate (one phase 3 RCT; product discontinued) · Osteoporosis or other uses: No human data reviewed

This page reports what studies used. It is not dosing advice.

Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source

About the evidence: one pivotal RCT on a surrogate endpoint (lower supplement needs); the product is no longer made.

What is it?

Related pages: palopegteriparatide, teriparatide, abaloparatide.

Does it work?

Human REPLACE (24 weeks): 53% vs 2% met the composite goal. ^{R4, R10}
🟨 Phase 4 open-label study (1 year, 22 patients): 95.5% had calcium in the target range at the end. ^R5

Is it safe?

Boxed warning: osteosarcoma; REMS-restricted. ^R3
Low and high blood calcium were common risks in trials. ^R4

Gray-market vials: extra risks

A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe.

Is it legal?

US: Natpara (BLA125511) was discontinued; Takeda ended manufacturing at the end of 2024. openFDA still lists the application. ^{R1, R2, R3} Palopegteriparatide (Yorvipath) is the current approved PTH replacement.
Compounding: not on FDA's 503A or 503B bulk-substance category lists and not on FDA's compounding safety-risk page. ^{R6, R7, R8}
Sport: not named on WADA's 2026 Prohibited List. ^R9

Study details

These are amounts researchers used, not recommendations.

Study	People / model	Route	Amount used	Follow-up	Reported	Citation
REPLACE 2013	134 adults with hypoparathyroidism	SC	Titrated, per former label	24 weeks	53% vs 2% met goal	PMID 24622413
Khan 2024 (phase 4 extension of PARALLAX)	22 adults	SC	Titrated, per study	1 year, open-label	95.5% calcium in target range	PMID 38741607

Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 27, 2026)

^R1 Drugs@FDA, Natpara (parathyroid hormone), application BLA125511 (openFDA drugsfda record checked Oct 27, 2026). https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=BLA125511
^R2 Takeda. Takeda to discontinue manufacturing of NATPAR/NATPARA (parathyroid hormone) for injection at the end of 2024. Statement, Oct 4, 2022. https://www.takeda.com/en-us/newsroom/statements/2022/takeda-to-discontinue-manufacturing-of-natpar-natpara/
^R3 FDA. Letter to patients about the discontinuation of Natpara (parathyroid hormone) for injection. https://www.fda.gov/media/182120/download
^R4 Mannstadt M, et al. Lancet Diabetes Endocrinol. 2013. PMID 24622413
^R5 Khan AA, et al. JBMR Plus. 2024. PMID 38741607
^R6 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
^R7 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
^R8 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
^R9 WADA. The 2026 Prohibited List, full list checked; compound not named. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
^R10 ClinicalTrials.gov NCT00732615, REPLACE, phase 3, completed (CT.gov API v2, checked Oct 27, 2026). https://clinicaltrials.gov/study/NCT00732615

Disclaimer

This page is for education and harm reduction, not medical advice or a recommendation to use Parathyroid hormone (PTH 1-84, Natpara). This is a prescription medicine. Use it only under the care of a licensed clinician; do not buy it from research-chemical or gray-market sellers. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).