Hyperthyroidism caused by TSH-producing adenoma

Objectives. To present a new case of central hyperthyroidism caused by thyrotropin (TSH)-producing adenoma.Design. Case report.Setting. Departments of Internal Medicine, Diagnostic Radiology and Biochemistry, University of the Orange"Free State, Bloemfontein.Subject and outcome measures. A 36-year-old woman with symptoms and signs of hyperthyroidism was diagnosed as having an elevated free thyroxine (T4) level and nonsuppressed THS level.Results. Magnetic resonance imaging (MRI) examination of the pituitary gland showed a macro-adenoma of the adenohypophysis, 2 x 1.5 x 1 cm in diameter. The patient did not have any other alteration in secretion of the pituitary hormones. Hyperthyroidism was successfully treated with adenomectomy. The only postoperative complication was permanent diabetes insipidus.Conclusion. THS-producing adenomas are rare but possible causes of hyperthyroidism. MRI examination helps to distinguish TSH adenoma from another form of central hyperthyroidism, namely the syndrome of pituitary resistance to thyroid hormone (PRTH)