Myotonic dystrophy: effect of testosterone on total body potassium and on creatinine excretion.

Muscle wasting in myotonic dystrophy appears to reflect impaired anabolism rather than accelerated catabolism. We therefore investigated the effects of testosterone, an anabolic hormone, on muscle mass as estimated by creatinine excretion and total body potassium in nine patients with myotonic dystrophy. Weekly injections of testosterone for 10 to 13 weeks increased both creatinine excretion (19%) and total body potassium (16%) in all patients. Metabolic balance data showed a confirmatory accretion of nitrogen, potassium, and phosphorus. Because testosterone increases indirect measures of muscle mass, it may deserve a therapeutic trial in myotonic dystrophy.