Hypogonadotropic hypogonadism is the consequence of FSH and LH deficiency leading to testicular or ovarian dysfunction. The diagnosis should be considered when there is a complete absence of pubertal development in both sexes. Hypogonadotropism, that occurs after puberty, is revealed by secondary amenorrhea in women, decreased libido in men. The hormonal diagnosis is easy in the complete forms with usually undetectable plasma LH, FSH and sex steroid levels. In the partial forms, plasma gonadotropin levels may be in the low normal range with slightly decreased plasma sex steroid levels. Gonadotropin deficiency may be isolated, congenital and of genetic origin. In acquired forms, panhypopituitarism and mass lesions of the hypothalamic pituitary sites must be diagnosed by magnetic resonance imaging and hormonal testing. Treatment requires only substitution when fertility is not sought. In the treatment of infertility, the use of pulsatile modes of GnRH administration is remarkably successful in women, as well as exogenous gonadotropins in both sexes.