A case of cushing syndrome with both secondary hypothyroidism and hypercalcemia due to postoperative adrenal insufficiency.

A 48-year-old woman was referred to our hospital because of secondary hypothyroidism. Upon admission a left adrenal tumor was also detected using computed tomography. Laboratory data and adrenal scintigraphy were compatible with Cushing syndrome due to the left adrenocortical adenoma, although she showed no response to the TRH stimulation test. Hypercortisolism resulting in secondary hypothyroidism was diagnosed. After a left adrenalectomy, hydrocortisone administration was begun and the dose was reduced gradually. After discharge on the 23rd postoperative day, she began to suffer from anorexia. ACTH level remained low, and serum cortisol, free thyroxine and TSH levels were within the normal range. Since her condition became worse, she was re-admitted on the 107th postoperative day at which time serum calcium level was high (15.6 mg/dl). Both ACTH response to the CRH stimulation test and TSH response to the TRH stimulation test were restored to almost normal levels, but there was no response of cortisol to CRH stimulation test. We diagnosed that the hypercalcemia was due to adrenal insufficiency. Although the serum calcium level decreased to normal after hydrocortisone was increased (35 mg/day), secondary hypothyroidism recurred. It was suggested that sufficient glucocorticoids suppressed TSH secretion mainly at the pituitary level, which resulted in secondary (corticogenic) hypothyroidism. However, both postoperative glucocorticoid deficiency and adequate amounts of thyroxine due to the elimination of inhibition of TSH secretion by glucocorticoids might cause hypercalcemia possibly through increased bone reabsorption of calcium.