SUBSTANTIAL RISE OF PLASMA BETA-ENDORPHIN LEVELS AFTER INSULIN-INDUCED HYPOGLYCEMIA IN HUMAN-SUBJECTS

To elucidate whether insulin-induced hypoglycemia enhances the release of .beta.-endorphin in man, plasma extracts obtained from healthy subjects and patients with Graves'' disease before and 45 min after insulin injection were subjected to gel chromatography, and the fractions obtained were measured by radioimmunoassay for .beta.-endorphin. In 4 healthy subjects, basal plasma .beta.-endorphin levels were > 3 to 3.1 pg/ml and the levels rose substantially to 47.5 .+-. 12.4 pg/ml (mean .+-. SE) 45 min after insulin injection. Basal plasma .beta.-endorphin levels in 3 hyperthyroid patients (< 3 to 3.8 pg/ml) did not not seem to be different from those in healthy subjects; the rise after insulin injection tended to be higher in cases of hyperthyroidism, with a peak value of 68.5 .+-. 9.7 pg/ml. Plasma .beta.-lipotropin and ACTH levels also rose in parallel with .beta.- endorphin in response to insulin-induced hypoglycemia in both healthy subjects and hyperthyroid patients. .beta.-Endorphin, like ACTH or .beta.-lipotropin, is apparently released in human subjects by hypoglycemic stress.