A case of transient central hyperthyroidism.

Background: Thionamides are the main therapeutic arsenal for treating hyperthyroidism. Perhaps the first case of a patient who developed a transient pituitary hyperthyroidism after discontinuation of a lengthy intake of a thionamide is reported.

Case Report: A 48-year-old woman presented with menstrual irregularities when hypothyroidism with pituitary enlargement was detected. She had been undergoing treatment with methimazole for Graves's hyperthyroidism since the age of 34. Three months after discontinuation of methimazole she presented with clinical and laboratory evidence of thyrotoxicosis, with elevated thyroid-stimulating hormone (TSH) levels and blunted response to thyrotropin releasing hormone (TRH). This secondary hyperthyroidism was self-limited and resolved a few months later.

Conclusions: Chronic primary hypothyroidism caused by lengthy use of thionamides can result in pituitary hyperplasia and transient thyrotrope dysfunction.