Formation of adenomata in hypophyses of rats subjected to both subtotal thyroidectomy and administration of 131-I, and its prevention by feeding of desiccated thyroid.

as well as benign and nialignant neopla.sms develop ill thyroid glands of Irlice and rats in which, for prolonged periods, a state of thyroxine deficiency has been estab lished by any one of the following means : the feeding of a low-iodine diet (1, 2) ; the administration of anti-thyroid substances (5, 15, 25) ; irradiation of the gland by 131J, astatine (211At), or X-rays (7, 12, 14, 19) ; and subtotal thyroidectomy (6, 14). There is good evidence for the belief that the neopla.st.ic changes should be attributed to the hyperplasia of thyrotropic hormone (TSH4)-producing cells in the anterior pituitary glands of the animals suffer ing from long-terni thyroxine deficiency. Assays of TSH contetits of the hypophysis and blood, as well as cytologic