Intestinal calcium absorption in patients with hyperthyroidism.

Intestinal 47Ca absorption was measured at 2 and 24 h after isotope ingestion in six patients with hyperthyroidism and seven normal subjects. Although 47Ca absorption was not different at 2 h, it was significantly lower (P < 0.01) after 24 h in the patients with hyperthyroidism. Factors related to the effects of thyroid hormone on intestinal function, in addition to abnormalities of vitamin D metabolism, are probably responsible for the defect.