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FDA-approved
Bones & muscles
Parathyroid hormone
Also called PTH(1-84)
Parathyroid hormone (Natpara) is an FDA-approved replacement for hypoparathyroidism. Learn how it works, trial results, and the boxed warning.
- Reviewed by
- William Maish, MD MBA MPH, Clinical Product Lead
- Published
- October 5, 2026
- Last updated
- October 5, 2026
Key takeaway
Parathyroid hormone (the full-length rhPTH(1-84) product, sold as Natpara) is a hormone replacement for people with hypoparathyroidism, a condition in which the parathyroid glands do not make enough of the hormone that controls calcium. It replaces the missing hormone to help maintain blood calcium. As of 2026 it has been FDA-approved in the U.S. since 2015, carries a boxed warning about a rat bone-cancer signal, and its U.S. supply has been limited as the manufacturer winds the product down.
What is parathyroid hormone?
The parathyroid hormone product Natpara is a recombinant copy of the full 84-amino-acid human hormone, rhPTH(1-84), that the parathyroid glands normally release to keep blood calcium in a healthy range. In hypoparathyroidism, those glands are missing or underactive, and patients must rely on large doses of calcium and active vitamin D that are hard to balance. Natpara replaces the hormone itself. It was approved in the United States in 2015.
How does parathyroid hormone work?
Parathyroid hormone binds the PTH-1 receptor and raises blood calcium through several routes:
- It increases calcium reabsorption in the kidney.
- It stimulates the kidney to activate vitamin D, which boosts calcium absorption from the gut.
- It mobilizes calcium from bone.
Replacing the hormone in hypoparathyroidism restores this physiologic control, which calcium and vitamin D supplements alone cannot fully reproduce.
The clinical goal is to maintain normal calcium while reducing the heavy supplement burden these patients otherwise carry. In the REPLACE trial, a majority of patients on rhPTH(1-84) achieved at least a 50 percent reduction1 in their calcium and active vitamin D doses while keeping blood calcium stable, compared with almost none on placebo.
Is it FDA-approved?
Yes. Parathyroid hormone (Natpara) was approved by the FDA in 2015 for hypoparathyroidism. It carries a boxed warning about osteosarcoma seen in rats and is available only through a restricted program. Its U.S. availability has been limited following a 2019 recall over a manufacturing issue and the manufacturer's decision to discontinue the product; the newer long-acting agent palopegteriparatide (Yorvipath) has since been approved for the same condition.
What is parathyroid hormone prescribed for?
Natpara is used as an add-on to calcium and active vitamin D to control low blood calcium in people with hypoparathyroidism who are not well managed on supplements alone. Because of its restricted program and limited supply, treatment decisions are individualized with a specialist.
What are the side effects?
Common side effects include:
- Tingling sensations (paresthesia)
- High or low blood calcium
- Headache and nausea
- Increased calcium in the urine
More serious considerations include:
- A boxed warning about osteosarcoma based on rat studies, which is why it is used under a restricted program
- Swings in calcium when doses are started, changed, or interrupted
Sources: FDA prescribing information for Natpara; Mannstadt et al. (2013), the REPLACE trial. PubMed-indexed studies are cited by DOI where used. This article is for educational purposes only and is not medical advice.