Hypogonadism (Loss of LH/FSH)
Hypogonadism is separated into primary hypogonadism (resulting from dysfunction of the testis or ovary) or central hypogonadism (resulting from pituitary or hypothalamic dysfunction that leads to loss of LH and FSH). Causes of hypogondaism include genetic, menopausual, autoimmune, viral, radiation, and chemotherapeutic agents. Central hypogonadism is often due to pituitary adenomas. Through compression of the gland, these tumors can cause destruction of pituitary tissue or interference with GnRH input from the hypothalamus. Gonadotropin dysfunction is the second most common hormonal disorder from compression of the pituitary gland from a pituitary adenoma after GH suppression. Hypothalamic disorders such as tumors and hypothalamic amenorrhea, as well as exposure to radiation, can lead to hypogonadism. Fasting, weight loss, anorexia nervosa, bulimia, exercise, or stressful conditions result in defects in pulsatile GnRH secretion ("hypothalamic amenorrhea"). Elevated prolactin levels can also suppress GnRH pulses and lead to hypothalamic hypogonadism. Diagonisis requires measurement of LH, FSH, and testosterone or estrogen, with reference to age-adjusted normal values.
Hypogonadism in prepubertal children causes no symptoms, whereas in adolescents, it leads to delayed or absent sexual development. In adult women, hypogonadism causes amenorrhea, infertility, loss of libido, vaginal dryness, and hot flashes. Prolonged periods of hypogonadism can cause osteoporosis. In men, hypogonadism leads to loss of libido, erectile dysfunction, and infertility.
Treatment of hypogonadism in men and premenopausal women is effectively accomplished by replacement hormonal therapy. Fertility can be restored by administration of hCG, which acts like LH, often in combination with FSH, or by the pulsatile administration of GnRH.