The combined stimulation test using TRH, LHRH and insulin has allowed investigation of the reserve of all pituitary tropic hormones under physiological and pathological conditions. To evaluate the diagnostic efficacy of this test for
differentiating the
underlying causes of hypopituitarism, we analyzed retrospectively the results of these tests done in 81 patients with proven hypothalamo-pituitary disorders.
1. In 15 patients with Sheehan's syndrome as a typical type of primary hypopituitarism, responses of FSH, LH and TSH in 11 to 12 cases(73-80%). Incremental response of
prolactin(PRL) to TRH was diminished or absent in 13 cases(80%). In 14 patients with hypothalamic diseases, including 10 cases of craniopharyngioma, as a representative secondary hypopituitarism, the basal PRL levels were abnormally elevated in
12
cases(86%) and both responses of PRL to TRH and of GH to hypoglycemia were blunted in 11 cases(79% in both).
The frequency of impaired cortisol secretion was 50%, followed by LH, TSH and FSH secretion : overall frequency much lower than in Sheehan's syndrome.
2. In 18 acrometalics with pituitary adenoma, basal GH levels were abnormally elevated in 14 cases(78%) and incremental responses of GH to hypoglycemia were found in 13(72%). Hyperprolactinemia was accompanied in 8 (44%). In 18 patients with
prolactinoma, basal PRL levels were moderately to markedly elevated in all of them(100%) and responses of PRL to TRH were blunted in 13(72%). The frequency of impaired secretion of H, FSH, cortisol and TSH was slightly higher in acromegalics than
in
patients with prolactinoma.
3. The frequency of impaired secretion of GH, cortisol and LH tended to slightly higher in patients with pituitary adenoma associated with visual field defect than those without visual field defect.
These results suggest that the combined pituitary stimulation test will give us some of reliable information for evaluating the underlying causes of hypopituitarism.
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