Transient thyrotoxicosis after unilateral adrenalectomy in two patients with Cushing's syndrome

We found transient hyperthyroidism in the course of hydrocortisone withdrawal in two patients who had undergone unilateral adrenalectomy to resect cortisol-hypersecreting adenoma. A 38-yr-old woman showed clinical thyrotoxicosis 3 months after the operation. Serum T4, T3 and TBG levels were 11.9 micrograms/dl, 310 ng/dl and 16.5 micrograms/ml, respectively. She was given methimazole (MMI) 15 mg/day for 4 weeks. After the cessation of MMI treatment, she eventually recovered to the euthyroid state. The other patient, a 34-yr-old man showed very mild clinical symptoms of hyperthyroidism 2 months after the operation. Serum T4, T3 and TBG levels were 10.4 micrograms/dl, 240 ng/dl and 14.5 micrograms/ml, respectively. In this case, no antithyroid drug was given. Two to three months after the onset of hyperthyroidism, he returned to the euthyroid state spontaneously. We carefully eliminated the possibility of factitious thyrotoxicosis in both cases. They had neither neck pain nor fever. Both had low radioactive iodine uptake by the thyroid. Therefore, we diagnosed them as painless thyroiditis induced after the resection of hypersecreting adrenal adenoma.