Human Hepatic Testosterone A-Ring Reductase Activity: Effect of Medroxyprogesterone Acetate

Testosterone A-ring reductase activity was measured in human liver obtained from 6 normal volunteers by aspiration liver biopsy. The base line enzyme activity varied between 62 and 132 nmoles of testosterone metabolized per hr per mg liver protein. Administration of medroxyprogesterone acetate resulted in a 200–500% increase in reductase activity. This was associated with a 28–58% rise in the metabolic clearance rate of testosterone. Medroxyprogesterone acetate appears to increase the metabolic clearance rate of testosterone by raising the A-ring reductase activity.