Parathyroid hormone

At a glance

Overview

Natural PTH is released by the parathyroid glands when blood calcium falls. This entry focuses on the full-length 84-amino-acid hormone and the recombinant medicine Natpara, rather than the separately listed PTH fragments and prodrugs. Natpara was approved as an adjunct to calcium and vitamin D for hypocalcemia in hypoparathyroidism when conventional treatment was inadequate. The product subsequently faced a US recall and prolonged supply constraints. Takeda announced global manufacturing discontinuation at the end of 2024 and no US re-commercialization. Consequently, a directory entry marked historically approved does not imply that routine prescribing and supply remain available in 2026.

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How it works

PTH activates PTH1 receptors in renal and skeletal tissue. It promotes calcium retention in the kidney, increases phosphate excretion, and stimulates production of active vitamin D. Bone effects depend on the timing and intensity of exposure: physiologic replacement, intermittent anabolic therapy, and chronic excess are not biologically equivalent. Full-length PTH and the active 1–34 fragment share receptor activity but differ in molecule, formulation, and clinical evidence.

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Historical approved use

Natpara was approved to help control hypocalcemia in hypoparathyroidism as an adjunct to calcium and vitamin D. Because of potential osteosarcoma risk, its label reserved treatment for patients inadequately controlled with conventional therapy. This indication differs from using a PTH analog to build bone in osteoporosis.

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The REPLACE trial

The randomized REPLACE study examined whether recombinant PTH(1–84) could reduce oral calcium and active vitamin D requirements while maintaining calcium control. More treated participants achieved the combined endpoint than placebo recipients. This provides clinical replacement evidence, but does not prove that all symptoms or long-term renal complications resolve.

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Safety during treatment and transitions

Important risks include severe hypercalcemia, severe hypocalcemia when treatment is interrupted, hypersensitivity, and digoxin interactions. The historical label carried a boxed osteosarcoma warning based on animal findings and required a restricted program. Transitioning away from a PTH product requires a supervised mineral-management plan because supplements alone may need substantial adjustment.

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What happened to Natpara?

Takeda’s announcement attributes discontinuation to unresolved product-specific supply issues and describes continued supply only while remaining inventory permits. Manufacturing cessation is separate from the hormone’s established physiology or the efficacy of other approved PTH products. The later long-acting product palopegteriparatide should be read under its own profile and current label.

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Does Natpara’s discontinuation mean all PTH replacement stopped?

No. Natpara is a specific recombinant PTH(1–84) product affected by manufacturing and supply problems. Other PTH-based medicines have separate development programs and approvals. Their availability, indications and safety instructions must be checked individually; the disappearance of one product does not establish equivalence of another.

Supporting sources [1] [3]