A 13 year-old boy was referred to our hospital because of several months of school performance deterioration, behavioral changes and secondary enuresis. Hyperthyroidism, diabetes insipidus and hypopituitarism due to thyrotropin secreting pituitary macroadenoma were found. Six weeks of therapy with octreotide failed to reduce the serum TSH levels and the tumor size. Transsphenoidal pituitary surgery had a transient effect on serum TSH levels as the patient redeveloped hyperthyroidism with elevated serum TSH levels. Several months had elapsed from the time the patient first presented with the symptoms to the time the diagnosis was made. Thyrotropin secreting pituitary adenoma is a rare cause of hyperthyroidism. Recognizing the signs of the disease might lead to early diagnosis and might improve the prognosis.