Estrogen treatment in eugonadal men diminishes libido, whereas libido is preserved by estrogens in orchidectomized transsexuals as well as in cases of aromatase deficiency. Hypothalamic hypogonadism can be caused by stress, depression, anorexia or excessive exercise. It may result in erectile dysfunction and decreased libido. A 7 day trial of clomiphen (25 mg/day) can be used to test the responsiveness of the axis and may be continued for up to 6 months as a means to stimulation endogenous LH and testosterone secretion. Other antiestrogens such as raloxifen or anastrazol may have similar effects in obese men and in aging men with late onset hypogonadism (LOH).