Transient Graves disease developing after surgery for Cushing disease

A 49-year-old man, diagnosed as having Cushing disease in 1976 at the age of 26, underwent a Hardy operation 13 years after treatment with reserpine combined with pituitary radiation. In laboratory examinations before and 2 weeks after the successful surgery, the patient's serum thyroid hormones were found to be normal except for suppressed serum thyroid-stimulating hormone (TSH), and his serum anti-TSH receptor (TRAb) and anti-TSH receptor-stimulating antibodies (TSAb) were negative. Glucocorticoid supplemental treatment was withdrawn on the 15th day after surgery and was restarted on the 48th day, during which time there were no signs of an adrenal crisis. Sinus tachycardia, fine finger tremor, and enlarged thyroid gland, approximately the size of a thumb head, were observed on the 140th day after surgery. Thyrotoxicosis with increased serum TSAb and TRAb and high 24-h thyroid uptake of 123I was noted, indicating a diagnosis of Graves disease. No special treatment was prescribed, but his serum thyroid hormone levels started to decrease on the 140th day after the operation and returned to normal on the 520th day. Serum TRAb also spontaneously decreased, but the timing of the peak of serum TRAb was delayed 230 days from that of the thyroid hormones. This is the first reported case of Graves disease after successful surgery for Cushing disease. We presume that a latent autoimmune process in the thyroid, suppressed by hypercortisolism, developed into overt Graves disease after the abrupt reduction of plasma glucocorticoid levels induced by surgery.