What is hypoparathyroidism?
Hypoparthyroidism is a deficiency of parathyroid hormone that causes abnormal metabolism of calcium and phosphorus. Parathyroid glands consist of four pea-shaped glands located on the back and side of the thyroid gland. The gland produces parathyroid hormone which, along with vitamin D and calcitonin, are important for the regulation of the calcium level in the
body. Hypoparathyroidism affects both males and females of all ages. The parathyroids produce parathyroid hormones that regulate blood levels of calcium necessary for strong bones and teeth, nerve function, and blood clotting.
Hypoparathyroidism is a rare disorder associated with insufficient production of parathyroid hormone, the inability to make a usable form of parathyroid hormone, or the inability of kidneys and bones to respond to parathyroid hormone production. A deficiency of parathyroid hormone lowers blood calcium levels and raises phosphate levels. Hypoparathyroidism either may be inherited or acquired; the acquired form usually results from parathyroid surgery or an underlying disorder, such as cancer or neck trauma.
Parathyroid hormone (PTH) works in conjunction with vitamin D to regulate total body calcium. The body secretes PTH in response to hypocalcemia or hypomagnesemia; the hormone then stimulates osteoclasts to increase bone resorption. PTH also acts indirectly through the stimulation of adenyl cyclase to increase renal tubular calcium resorption and phosphate excretion. Finally, it activates the conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D, the active form of vitamin D that stimulates calcium and phosphate absorption from the GI tract.
Hypoparathyroidism can result in hypocalcemia, and it commonly is diagnosed during the workup for hypocalcemia. Pseudohypoparathyroidism describes hereditary conditions that cause end organs to be resistant to PTH. |
