Plasma TSH and prolactin response to insulin induced hypoglycemia in patients with hypothalamic pituitary disorders.

Plasma TSH and prolactin (PRL) responses to insulin-induced hypoglycemia (ITT) were examined in 37 patients with various hypothalamic pituitary disorders. Four patients showed a definite TSH response to ITT. They were 2 patients with suspected pinealoma with diabetes insipidus (DI), a patient with pituitary adenoma and a patient with acute prophyria. A suspected hypothalamic dysfunction and a slightly impaired pituitary function manifested as GH deficiency were their common endocrinological features. On the contrary, plasma PRL response to ITT was noted in about one third of the patients examined, but no concomitant PRL response was observed in any of the patients with a definite TSH response. This suggested a different mechanism of TSH and PRL secretion may be different under this circumstance and a certain factor related to the hypothalamic disorder may play a modulating role in an unusual TSH response to hypoglycemia in these particular patients.