Effect of Testosterone on Jejunal Pyruvate Kinase Activities in Normal and Hypogonadal Males

Activities of jejunal glycolytic enzymes were measured in 6 normal and 7 testosterone deficient men on controlled diets before and after testosterone. Jejunal glycolytic enzymes were measured in the hypogonadal males after isocaloric diets: glucose, fructose, and both together. In comparison with normals, the hypogonadal males showed significantly decreased activities of jejunal pyruvate kinase, fructose-1-phosphate aldolase and fructose diphosphate aldolase (p < 0.001) and no significant difference in hexokinase. Both normal and hypogonadal males showed significantly increased activity of pyruvate kinase after oral testosterone (10 mg/day for 2 days). Intramuscular testosterone increased the activity of pyruvate kinase in the hypogonadal males. Dietary changes produced less adaptive changes in jejunal glycolytic enzyme activities in hypogonadal males than in normal subjects. This lack of adaptive change may be related to testosterone deficiency. We conclude that testosterone-deficient adult males have decreased activities of certain jejunal glycolytic enzymes, which are increased by the administration of oral and intramuscular testosterone. Jejunal biopsy provides a useful means of studying the effect of hormones on human enzyme activities.