TSH-secreting adenoma: 2 case reports and a review of the literature.

TSH-secreting adenoma is a rare entity; a series of 69 cases has been collected by Faglia in 1989 and 78 new cases were published from 1987 to 1994. We report two new cases, which have been explored by octreoride scintigraphy before treatment with the SRIH analogue. An in vitro SRIH receptor study was also performed in the first patient. This patient, a young man, suffered from hyperthyroidism with enhanced FT3 and FT4 concentrations without decreased TSH values. Plasma alpha subunit level was slightly increased. He had a pituitary tumor, positive in Octreoscan but responded partially to treatment by SRIH analogue. The tumor was in part surgically removed and the SRIH receptors revealed a homogeneous density; their number was equal to those of GH-secreting tumor but their affinity was lower. The second patient, an elderly woman was nor surgically treated because the octreotide treatment dramatically improved both tumor volume and thyroid hormone or alpha subunit plasma levels. The tumor, associated to a probable meningioma was also positive in Octreoscan and was characterised by a highly increased alpha subunit plasma level. These results are discussed by comparison with those of the literature.