Sarcoidosis of the thyroid and kidneys and calcium metabolism.

In sarcoidosis, the thyroid and the kidneys are infrequently affected. Clinically recognizable thyroid involvement occurs in < 1% of sarcoidosis patients. Hyperthyroidism, myxodema, and thyroid occur with an equal frequency. It is important to distinguish sarcoidosis of the thyroid from other infections and disorders of the gland. Renal involvement may present as granulomatous infiltration of the renal parenchyma, glomerulonephritis, renal arteritis, and nephrocalcinosis or renal stones. The latter are due to abnormalities of calcium metabolism. Hypercalcemia occurs in about 10 to 13% of sarcoidosis patients; hypercalciuria is three times more frequent. Calcium abnormalities may precede, follow, or occur at any time during the course of sarcoidosis. An endogenous overproduction of 1,25-dihydroxyvitamin D [1,25-(OH (2))-D (3)] by granulomatous tissue and activated macrophages results in an increase of intestinal absorption of calcium. Corticosteriods, chloroquine, and hydroxychloroquine subdue 1,25-(OH (2))-D (3) production and correct hypercalcemia and hypercalciuria.