Plasma non-esterified fatty acid levels in hypopituitary subjects.

Abstract

SUMMARY Changes in the plasma levels of non-esterified fatty acids (NEFA) in a group of patients with proven hypopituitarism have been compared with those found in control subjects during prolonged fasting, after the injection of insulin and after the oral administration of glucose with and without the previous administration of insulin. During a 4 hr. prolongation of an overnight fast plasma NEFA levels increased at a significantly slower rate in the patients with hypopituitarism. The intravenous injection of insulin was followed by a prompt fall in NEFA levels in the control group, and by a rapid return to or above original values. The recovery was consistently and markedly impaired in the patients with hypopituitarism and this abnormality differentiated them more clearly from the normal subjects than the abnormality in their plasma sugar response to insulin. The patients with pituitary hypofunction had a flat plasma sugar curve after the oral administration of glucose, but there were only minor differences from the normal plasma NEFA levels. Previous insulin administration impaired glucose tolerance in normal subjects and resulted in a more rapid late return of NEFA levels than after the administration of glucose alone. This late rise in NEFA did not occur in the hypopituitary group. The results obtained support the concept that pituitary integrity is required for normal fat mobilization. The consistency of the changes suggests that tests based on plasma NEFA measurements may provide a useful indirect means of diagnosing pituitary hypofunction.