Thyrotropin-secreting pituitary adenomas: biological and molecular features, diagnosis and therapy.

ABSTRACT

Central hyperthyroidism due to a thyrotropin (TSH)-secreting pituitary adenoma is a rare cause of hyperthyroidism, representing 0.5-1.0% of all pituitary adenomas. The etiopathogenesis of TSH-secreting-adenomas is unknown and no definite role for various oncogenes has been proven. Patients with TSH-secreting adenoma usually present with signs and symptoms of hyperthyroidism milder than those in patients with hyperthyroidism of thyroid origin, in addition to symptoms secondary to mass effects of the pituitary tumour. Mixed pituitary tumours co-secrete growth hormone and prolactin. The characteristic biochemical abnormalities are normal or high serum TSH concentrations in the presence of elevated total and/or free thyroid hormones concentrations. Measurement of markers of peripheral thyroid hormone action and dynamic tests may aid in the differential diagnosis with the syndrome of resistance to thyroid hormone. Neuroimaging is fundamental to visualize the pituitary tumor. Therapy of TSH-secreting adenomas can be accomplished by surgery, radiation therapies, and medical treatment with somatostatin analogs or dopamine agonists. Nowadays, and in contrast with the first reports on this rare disease, most patients are well controlled by current therapies.