Teriparatide (terr-ih-PAR-a-tyd) is synthetic human parathyroid hormone used by injection as a test to help diagnose problems of the parathyroid gland. Studies have measured the use of this drug to help people with moderate to severe osteoporosis. View a slide show at the Food and Drug Administration web site of the Endocrinologic and Metabolic Drugs Advisory Committee Meeting.

Indication

Hypoparathyroidism, idiopathic or Pseudohypoparathyroidism. Indicated to assist in confirming a preliminary diagnosis based on serum immunoreactive parathyroid hormone (iPTH) values in patients presenting with clinical or laboratory evidence of hypocalcemia (total serum calcium below approximately 1.8 mmol per liter), when the low serum calcium is due to idiopathic hypoparathyroidism or pseudohypoparathyroidism, type 1 or type 2.

Pharmacokinetics

Administration of the exogenous human parathyroid hormone, teriparatide, distinguishes between hypoparathyroidism and pseudohypoparathyroidism by testing the patient’s responsiveness to parathyroid hormone (PTH). Teriparatide stimulates the urinary excretion of cyclic adenosine 3’, 5’-monophosphate (c AMP) and phosphate. Response values are calculated from the measurements of urinary c AMP, serum phosphate, and urinary phosphate, and corrected for creatinine excretion.

In patients with idiopathic hypoparathyroidism (a deficiency in PTH secretion), teriparatide will produce normal or increased responses in urinary c AMP and phosphate excretion. In contrast, patients with pseudohypoparathyroidism (a rare form of hypoparathyroidism resulting from target tissue resistance to PTH), because they are unable to respond to PTH, will exhibit a blunted to normal response in urinary c AMP excretion, depending on whether it is type 1 or type 2 pseudohypoparathyroidism, and a blunted phosphaturic response.