A subtle initial clinical presentation of a TSH-secreting PitNET.

Summary: Thyroid stimulating hormone (TSH)-secreting PitNETs, also called TSHomas, are rare benign pituitary tumors with an incidence of 1.0 per million population. They are generally diagnosed in the context of central hyperthyroidism and/or mass-effect central symptomatology (e.g. headache, bitemporal hemianopsia, and panhypopituitarism). Although TSHomas are more often macroadenomas than microadenomas at the time of diagnosis, diagnosing TSHomas may be challenging because laboratory findings and clinical presentation are not always obvious. The treatment of choice is the surgical resection of the adenoma. Learning points: TSHomas are mostly diagnosed as macroadenomas in the context of central hyperthyroidism and/or mass-effect central symptomatology. The classical pattern of central hyperthyroidism consists of elevated free thyroid hormones and inadequately normal or slightly increased TSH. If a TSHoma is suspected, the differential diagnosis of thyroid hormone resistance (RTH) must be excluded. Surgical resection is the first-line choice of therapy for TSHomas. In cases of non-operable lesions or postoperative residual tumors, pituitary fractionated stereotactic radiotherapy, radiosurgery, and/or medical treatment with somatostatin analogs can be considered as alternatives. The management of TSHomas must happen in an interdisciplinary way.