Gonadal function in males with myotonic dystrophy.

Abstract

Serum FSH and/or LH concentrations were determined by radioimmunoassay in 39 males (ages 15–45 yr) with myotonic dystrophy and compared with serum FSH and/or LH concentrations in 35 normal males (ages 18–45 yr). Plasma testosterone concentrations were determined by competitive protein binding in 36 of the males with dystrophy and compared with those observed in 30 normal males. The mean serum FSH concentration (65.4 ± 17.0 mIU/ml) of 32 males with myotonic dystrophy was significantly greater (p < 0.005) than the mean serum FSH concentration (9.3 ± 3.1 mIU/ml) of 28 normal males. All serum FSH concentrations (18.3 to 92.5 mIU/ml) were greater than the range of serum FSH concentrations (5.2 to 14.5 mIU/ml) of normal males. The mean serum LH concentration (20.1 ± 13.9 mIU/ml) of 39 males with myotonic dystrophy was significantly greater (p < 0.005) than the mean serum LH concentration (9.2 ± 5.1 mIU/ml) of 35 normal males, and 14 of the 39 had serum LH concentrations which were greater than 2 standard deviations (20.0 to 74.3 mIU/ml) above the mean of normal males. The mean plasma testosterone concentration (398 ± 151 ng/100 ml) of 36 males with myotonic dystrophy was significantly less (p < 0.005) than the mean plasma testosterone concentration (563 ± 128 ng/100 ml) of 30 normal males, and eight of the 36 had testosterone concentrations which were more than 2 sd below the mean concentration of normal males. The data are consistent with the concept that primary gonadal failure accounts for the hypogonadism in patients with myotonic dystrophy. The determination of serum FSH concentrations may be a helpful supplementary aid in the diagnosis of myotonic dystrophy.