Thyrotropin-secreting pituitary tumors are rare causes of hyperthyroidism and account for less than 1% of all pituitary adenomas. The number of reported cases increased over the last few years as a consequence of the routine use of ultrasensitive immunometric assays for measuring thyrotropin levels. In the clinical practice, thyrotropin secreting adenomas must be considered in case of inappropriately normal to elevated thyrotropin in the presence of elevated free serum thyroid hormone levels. The authors present the case history of a middle aged female patient, who suffered from hyperthyreodism caused by a thyrotropin-secreting pituitary macroadenoma. After transient thyreostatic treatment, radical neurosurgical removal of the tumor was performed. The pituitary surgery was effective in restoring the patient’s euthyreodism. The postoperative pituitary function remained intact. During follow-up, the recurrence of the disease was not detected. In our case report, the difficulties in the differential diagnoses are also discussed. Orv Hetil. 2020; 161(12): 474-478.