All peptides / Muscle and bone
Parathyroid hormone
PTH (recombinant)
Also Natpara, PTH, rhPTH(1-84), rhPTH 1-84, Parathyroid hormone 1-84, Recombinant parathyroid hormone
- Evidence
- AStrong human evidence
- FDA status
- FDA approvedas of 2026-10-26
- Route
- Injection
- Studies cited
- 1 human0 animal or cell
An injection for people whose body makes too little parathyroid hormone, so they need fewer calcium pills. In 134 adults it worked, but it is no longer made.
Sold for
Natpara was the first hormone replacement for hypoparathyroidism, promising freedom from the calcium and vitamin D pill burden.
Studies say
A 24-week placebo-controlled trial showed about half of patients could cut their supplements by half or more while keeping calcium normal, supporting the approval; supply problems ended the product, and efficacy was not the cause.
Why grade A. The approval rests on REPLACE, a randomized, double-blind, placebo-controlled phase 3 trial in 134 adults with hypoparathyroidism, which met its primary endpoint of reducing conventional therapy while holding calcium in range. The grade applies to that use. The drug's practical availability, not its evidence, is what has collapsed. 1
FDA. Recombinant parathyroid hormone was approved in 2015 as Natpara for hypocalcemia in hypoparathyroidism that cannot be controlled with calcium and active vitamin D alone, with a boxed warning for osteosarcoma and a restricted distribution program. Takeda recalled it in the United States in 2019 over particles from the cartridge septum and announced in 2022 that manufacturing would end globally at the end of 2024. 12
Written from 2 cited sources. Fact-checked 2026-10-27: 12 claims checked, 1 corrected. Last refreshed 2026-10-27. Not physician reviewed.
What this means for you
- What people take it for
- Keeping calcium normal with fewer pills.
- Can a US doctor prescribe it?
- No. It was approved in 2015 for low calcium from underactive parathyroid glands, but it is being discontinued worldwide.
- Properly tested in people?
- Yes, in large controlled trials: a 134-adult trial.
Evidence checklist
- Randomised controlled trial REPLACE, double-blind, placebo-controlledyes
- Human study over 100 people REPLACE 134 adultsyes
- More than one research group One pivotal trial citedno information
- Clinical outcomes, not surrogate markers Lower supplement need; calcium stayed in rangeno
- Human safety data beyond case reports Trial data and osteosarcoma boxed warningyes
Drawn from the cited studies below. A dash means the sources give no information.
What it is
Parathyroid hormone is the 84-amino-acid hormone made by four small glands behind the thyroid. It is the body's main regulator of blood calcium. The recombinant drug, PTH(1-84), is identical to the natural molecule and was developed by NPS Pharmaceuticals, later acquired by Shire and then Takeda, as a once-daily injection called Natpara. 12
Hypoparathyroidism, most often caused by damage to the glands during thyroid surgery, leaves patients with low calcium and high phosphate. Before Natpara it was the last classic hormone deficiency without a replacement therapy; patients relied on large doses of oral calcium and the active vitamin D compound calcitriol, which often fails to prevent symptoms and raises urinary calcium. 1
How it works
PTH raises blood calcium through three routes: it releases calcium from bone, it makes the kidney reabsorb calcium and excrete phosphate, and it activates the enzyme that converts vitamin D into its active form so the gut absorbs more calcium. Replacing the hormone restores all three at once, which is why patients on it can cut back the supplements that only addressed intake. The limitation of a once-daily injection is that natural PTH is secreted continuously, so levels on Natpara rose and fell through the day. 1
What human research shows
REPLACE enrolled 134 adults with hypoparathyroidism and randomized them to PTH(1-84) or placebo for 24 weeks, with active vitamin D and calcium tapered as the study drug was adjusted. The primary endpoint was a 50 percent or greater reduction in both oral calcium and active vitamin D while keeping blood calcium in the target range. About 53 percent of patients on PTH met it against about 2 percent on placebo. Many patients on PTH were able to stop active vitamin D entirely. 1
The trial did not show improvement in urinary calcium, which some had hoped for, and later analyses of blood calcium through the day showed considerable fluctuation. These gaps are part of why the longer-acting successor palopegteriparatide was developed. 1
| Study | Model | Finding |
|---|---|---|
| REPLACE phase 3 (Mannstadt 2013) | Humans, n=134 adults with hypoparathyroidism, randomized double-blind placebo-controlled, 24 weeks | About 53 percent on PTH(1-84) versus 2 percent on placebo cut oral calcium and active vitamin D by half or more while maintaining normal blood calcium. 1 |
| Takeda discontinuation statement 2022 | Manufacturer announcement | Global manufacturing of Natpara to end at the close of 2024 after an unresolved particulate problem that caused the 2019 US recall. 2 |
Safety
Common adverse events in REPLACE were tingling and numbness, headache, nausea, and both high and low calcium, mostly during dose adjustment. Low calcium after a missed dose could be abrupt, because patients had reduced their supplements. The boxed warning for osteosarcoma comes from rat studies of PTH analogs; no human cases were attributed to the drug, but the FDA restricted it to patients who could not be managed otherwise and required enrollment in a risk-management program. 1
The 2019 US recall was a manufacturing problem: rubber particles shed from the cartridge septum into the drug. Takeda was unable to fix it, and in October 2022 said it would stop manufacturing worldwide at the end of 2024 and would not return the product to the US market, supplying remaining doses to existing patients under a special-use program until stock ran out. 2
Questions for your clinician
- Is any form of parathyroid hormone still available for me?
- How should my calcium be managed now?
- What does the osteosarcoma warning mean for me?
Questions people ask
Is Natpara still available?
Not for new patients. It was recalled in the United States in 2019, and Takeda announced that manufacturing would stop at the end of 2024 with remaining supply going to existing patients until it ran out. Palopegteriparatide (Yorvipath) was approved in 2024 as a replacement. 2
Why does PTH carry a cancer warning?
Rats given PTH or its analogs daily for most of their lives developed osteosarcoma. Humans have not shown this with two decades of teriparatide use, but the FDA requires the warning on the class and restricted Natpara to patients who could not be controlled on conventional therapy. 1
Is parathyroid hormone the same as teriparatide?
Teriparatide is the first 34 amino acids of the 84-amino-acid hormone and keeps the calcium-regulating activity. Natpara was the full-length molecule. Teriparatide is approved for osteoporosis; Natpara was approved for hypoparathyroidism. 1
Citations
- Mannstadt 2013, Lancet Diabetes Endocrinol: efficacy and safety of recombinant human parathyroid hormone (1-84) in hypoparathyroidism (REPLACE) doi.org
- Takeda 2022: statement on discontinuing manufacturing of Natpar/Natpara at the end of 2024 takeda.com