Thyrotropin- and Gonadotropin-Secreting Pituitary Adenomas

Abstract

Pituitary tumors that secrete growth hormone (GH), ACTH, and prolactin have been well characterized and result in distinct clinical syndromes. In contast, pituitary adenomas that secrete thyroid-stimulating hormone (TSH) or gonadotropins [follicle-stimulating hormone (FSH) and luteinizing hormone (LH)] are infrequent in clinical practice and consequently less well appreciated by clinicians managing patients with pituitary disorders. Caughey¹ drew attention to the fact that prolonged deprivation of the negative-feedback hormone secreted by the target organ can lead to hyperplasia and subsequently adenomatous transformation of the appropriate tropic-hormone-secreting adenohypophyseal cell. More recently, it has been recognized that primary tumors of the pituitary occur that secrete TSH or gonadotropins without prior thyroidal or gonadal failure. Further, it appears that pituitary adenomas may, on occasion, secrete peptides similar to, but not identical with, the authentic hormone, for although immunoreactivity is recognized by radioimmunoassay, the molecular species is not biologically active. Such circumstances may apply to all pituitary tumors including those that produce TSH and gonadotropins.