Parathyroid Hormone (rh PTH 1–84)

Natpara contains recombinant human PTH (1–84), the complete 84-amino-acid parathyroid hormone. When parathyroid glands are absent or underactive, patients can need difficult-to-balance calcium and active vitamin D supplementation; hormone replacement addresses the missing physiological signal. US approval was in 2015.

PTH-1 receptor activation increases renal calcium reabsorption, promotes renal activation of vitamin D and therefore intestinal calcium absorption, and mobilizes calcium from bone. Supplementation alone does not fully reproduce this feedback physiology.

REPLACE found that a majority receiving rh PTH (1–84) reduced both calcium and active-vitamin-D doses by at least 50% while maintaining serum calcium, compared with almost no placebo recipients. The goal was stable calcium with less supplement burden, not a generic bone-growth or wellness effect.

Natpara received FDA approval in 2015 as an adjunct to calcium and active vitamin D for hypocalcemia in hypoparathyroidism inadequately controlled with supplements. A boxed rat-osteosarcoma warning led to a restricted program.

US availability became limited after a 2019manufacturing-related recall and the manufacturer’s discontinuation decision. Approval is not proof of current stock. Specialist decisions reflect restricted supply; the newer long-acting palopegteriparatide/Yorvipath has since received approval for the same condition. The described Natpara regimen is daily subcutaneous treatment.

Common effects include paresthesia, hypercalcemia or hypocalcemia, headache, nausea and increased urinary calcium. The osteosarcoma warning derives from rat studies. Starting, changing or interrupting treatment can cause clinically important calcium swings, requiring product-specific monitoring.