Thyrotropin-Secreting Pituitary Adenomas

Thyrotropin-secreting pituitary tumors (TSH-omas or TSH-PitNET) are a rare cause of hyperthyroidism and account for about 1% of all pituitary adenomas. It is, however, noteworthy that the number of reported cases increased over the last few decades because of the improved awareness of this condition. Indeed, ultrasensitive TSH assays allow a clear distinction between patients with suppressed and those with non-suppressed circulating TSH concentrations, i.e., between patients with primary hyperthyroidism (Graves’ disease or toxic nodular goiter) and those with central hyperthyroidism (TSH-oma or resistance to thyroid hormone beta, RTHβ). Failure to recognize the presence of a TSH-oma may result in dramatic consequences, such as improper thyroid ablation that may cause the pituitary tumor volume to further expand. The presence of compressive manifestations (visual defects, headache) or clinical features of concomitant hypersecretion of other pituitary hormones (acromegaly, galactorrhea/amenorrhea) strongly supports the diagnosis of TSH-oma. Nevertheless, the differential diagnosis between TSH-oma and RTHβ may be difficult when the pituitary adenoma is tiny, or in the case of unrelated lesions such as an empty sella or pituitary incidentalomas. First-line treatment of TSH-omas is pituitary adenomectomy followed by irradiation in the case of surgical failure. However, medical treatment with long-acting somatostatin analogues (e.g. octreotide and lanreotide), are effective in reducing TSH secretion in more than 90% of cases with consequent normalization of FT4 and FT3 levels and restoration of the euthyroid state. For complete coverage of all related areas of Thyroidology please visit our Free web-site https://www.thyroidmanager.org. For complete coverage of all related areas of Endocrinology, please visit our on-line FREE web-text, WWW.ENDOTEXT.ORG.