[The influence of body weight upon the function of ovarian axis]

The relationship between the body weight and the function of hypothalamopituitary-ovarian axis was longtime studied. Frisch and Ravell (1971) have proposed the hypothesis that the onset of menarche is strong related to the achievement of a critical body weight. These authors observed that, despite the decrease in the last 120 years of the menarche age from 16.5 to 12.5 year-old, the body weight at which the menarche appears remains unchanged, 47.5 +/- 0.5 Kg. Many studies show the importance of both, body weight and fat mass percentage, in the appearance of menarche at puberty, or in the restoration of menses after the weight loss amenorrhea. Primary or secondary underweight amenorrhea can be associated to an eating disorder (anorexia nervosa, bulimia nervosa, or the alternation of these to clinical conditions), to severe exercise (athletes, gymnasts, dancers) or to malnutrition. The connected signal between metabolic status and reproductive function may be represented by the substances like: insulin, amino acids, IGFPB-I, leptin. The low levels of leptin were found in underweight female with oligo or amenorrhea. By the other hand, obesity is not a primary factor causing chronic anovulation. However, obesity may aggravate an already existing subtle defect in some women and result in amenorrhea.