What is secondary hyperparathyroidism?
Secondary hyperparathyroidism is a functional disorder of all of the four parathyroid glands due to a serious chronic kidney insufficiency. Secondary hyperparathyroidism is characterized by pronounced parathyroid gland hyperplasia resulting from
end-organ resistance to parathyroid hormone (PTH). The consequent hypersecretion of PTH depresses calcium levels. The most important cause of secondary hyperparathyroidism is chronic renal insufficiency.
In secondary hyperparathyroidism, pronounced hyperplasia of the chief cells of the parathyroid gland is often present. This hyperplasia usually affects all 4 glands, but 2 or even 3 may be spared. The cause of this asymmetric involvement is obscure. In exception cases, a true adenoma may develop.
The most common cause of secondary hyperparathyroidism is chronic renal disease, which is an occurrence in hemodialysis patients. Chronic hypocalcemia and secondary hyperparathyroidism may also occur in vitamin D deficiency, intestinal malabsorption syndromes with inadequate absorption of vitamin D and calcium, and pseudohypoparathyroidism. Other rare causes associated with secondary hyperparathyroidism include the long-term furosemide therapy in infants, the use of oral contraceptives, and idiopathic hypercalciuria.
Treatment involves correcting the underlying cause of the secondary hyperparathyroidism. Patients with vitamin D deficiency are treated with vitamin D or measures to correct malabsorption. Patients with cancer are usually treated surgically. Patients with chronic kidney failure are usually treated with calcium supplementation, phosphate restriction, and vitamin D analogs. Dialysis, kidney transplantation, or parathyroid surgery may be needed.