Delayed menarche and amenorrhea of college athletes in relation to age of onset of training.

Age at menarche and menstrual periodicity of 21 college swimmers and 17 runners were studied in relation to the age of initiating training. The 18 premenarche-trained athletes had a mean menarcheal age of 15.1 +/- 0.5 years, whereas the 20 postmenarche-trained athletes had a mean menarcheal age of 12.8 +/- 0.2 years, similar to that of the college control subjects, 12.7 +/- 0.4 years. Each year of training before menarche delayed menarche by five months (0.4 years). Of the premenarche-trained athletes, 61% had irregular menstrual cycles and 22% were amenorrheic, whereas 60% of the postmenarche-trained athletes had regular menstrual cycles and none were amenorrheic. Training increased the incidence of oligomenorrhea and amenorrhea among both premenarche- and postmenarche-trained athletes. Metabolic and hormonal changes consequent to an increased lean/fat ratio may explain these findings.