Nine patients suffering from hypothyroidism due to thyroid ectopia or hypogenesis, with a large sella turcica, were examined at adolescence or during adult life. TSH, prolactin and growth hormone function were studied. Basal plasma TSH, evaluated in 5 cases, was raised and responded explosively to stimulation with TRH. The administration of L-dopa was not associated with any notable changes in TSH. In one case, the chronic administration of l-T3 resulted in a fall followed by normalisation in plasma TSH levels. Basal plasma prolactin, explored in 6 patients, was high in 4 females and normal in 2 males. TRH stimulation resulted in a marked increased in prolactin in the female cases and a moderate increase in the male cases. L-dopa caused a fall only in high prolactin values. Stimulation of GH by argininehydrochloride, insulin hypoglycaemia and L-dopa gave variable responses. In one case, substitutive thyroid hormone therapy restored the GH response to L-dopa and arginine hydrochloride to normal. Paradoxically, GH increase following stimulation with TRH.