Hypercalcemia in concurrent hyperthyroidism and hyperparathyroidism

Abstract

A case of hyperthyroidism is presented in which the major symptoms were attributable to severe hypercalcemia. This is the 17th recording of concurrent hyperthyroidism and hyperparathyroidism. The evidence for a normal interaction between thyroid and parathyroid hormones in control of serum Ca is reviewed. Although skeletal Ca catabolism is a constant feature of hyperthyroidism, blood Ca levels are elevated only when homeostatic mechanisms are overloaded or damaged. Hypercalcemia may alter the clinical syndrome of thyrotoxicosis to resemble hyperparathyroidism. Marked hypercalcemia may complicate the differential diagnosis between hyperfunctlon of the thyroid and the parathyroid gland or concurrence of both Illnesses. The value of laboratory tests in this differential diagnosis is reviewed.