The response to TRH, LH-RH, metyrapone and vasopressin in patients with hypothalamo-pituitary disorders.

Abstract

Abstract. The effects of slow intravenous infusion of synthetic TRH on serum TSH and of synthetic LH‐RH on serum LH measured by radioimmunoassay were studied in healthy persons and in 36 cases with sellar tumours and other hypo‐thalamo‐pituitary disorders. The results were also compared with the responses to oral metyrapone and intravenous infusion of lysine‐8‐vasopressin, as tests for the hypothalamo‐pituitary‐adrenal regulation. 200 μg of TRH was found to give a mean increase of serum TSH of +10.4 μ/ml in eight males and of +15.7 μ/ml in nine females. LH‐RH infusion was found to give a mean increase of serum LH of ‐f‐1.78 ng/ml in six young males. The TRH test gave a pathologically low response in one out of nine patients with an intrasellar tumour. On the other hand in patients with a craniopharyngioma, which usually causes more pronounced pituitary destruction, the response was pathologically low in five out of six cases. A normal response to TRH was obtained in seven out of nine patients with disorders mainly affecting the hypothalamus. When twelve patients with pituitary adenomas were tested post‐surgery six patients gave a pathologically low TRH response. The response to LH‐RH was pathologically low in five out of eight cases with a pathologically low TRH response and normal in six out of six cases with a normal TRH response. However, there was a poor correlation between the results of these two tests and the vasopressin and metyrapone administration. This difference may be explained by the direct effect of the releasing hormones on the pituitary and the need for a certain hypothalamic function to obtain a response to the vasopressin and metyrapone tests.