The plasma sugar, free fatty acid, cortisol, and growth hormone response to insulin, and the comparison of this procedure with other tests of pituitary and adrenal function. II. In patients with hypothalamic or pituitary dysfunction or anorexia nervosa.

Abstract

Results from a comparative study using normal controls, and 34 patients with hypothalamic or pituitary dysfunction are presented. Patients with acromegaly were insulin resistant, but showed a normal plasma cortisol response when a large dose was used (0. 30 U/kg). Some of these patients failed to show a growth hormone increment above their high resting levels during the test, and the free fatty acid response appeared to be related to the presence or absence of such a rise. In all patients suspected of having hypothalamic or pituitary hypofunction (with the exception of one who had an isolated defect of adrenocorticotropin production) an impaired or absent growth hormone response to insulin was obtained. In some patients this was the only endocrine abnormality detected. The impairment of growth hormone secretion after insulin is of diagnostic value, since the appearance of this abnormality appears to precede evidence of gonadotropin, adrenocorticotropin, thyroid-stimulating hormone, or antidiuretic hormone deficiency. The free fatty acid response to insulin in these patients showed a consistent delay in the recovery phase. This finding proved a more sensitive index of hypo-function than did the extent and degree of the plasma sugar changes and may be of diagnostic value in hospitals without access to growth hormone determinations. The determination of plasma cortisol values throughout the insulin test had less diagnostic significance than the determination of growth hormone or free fatty acid levels, but was of value in determining whether these patients required cortisol replacement therapy. It was of particular use in detecting those patients with adequate basal adrenal function, but with limited pituitary reserve. The response to insulin proved of value in differentiating patients with hypothalamic or pituitary hypofunction and those with anorexia nervosa.