Hyperthyroidism caused by TSH-producing adenoma

Objectives. To present a new case of central hyperthyroidism caused by thyr otropin (TSH)-producing adenoma. Design. Case report. Setting. Departments of Internal Medicine, Diagnostic Radiology and Biochem istry, University of the Orange Free State, Bloemfontein. Subject and outcome measures. A 36-year-old woman with symptoms and signs o f hyperthyroidism was diagnosed as having an elevated free thyroxine (T-4) level and non-suppressed THS level. Results. Magnetic resonance imaging (MRI) examination of the pituitary glan d showed a macro-adenoma of the adenohypoyhysis, 2 x 1.5 x 1 cm in diameter . The patient did not have any other alteration in secretion of the pituita ry hormones, Hyperthyroidism was successfully treated with adenomectomy, Th e only postoperative complication was permanent diabetes insipidus. Conclusion, THS-producing adenomas are rare but possible causes of hyperthy roidism. MRI examination helps to distinguish TSH adenoma from another form of central hyperthyroidism, namely the syndrome of pituitary resistance to thyroid hormone (PRTH).