In women, hypogonadism results in amenorrhea (loss of menstrual periods) and may cause vaginal dryness and pain with intercourse. Men may experience symptoms of low testosterone, which include erectile dysfunction, low libido, depression, fatigue, loss of muscle mass, an increase in abdominal fat, and development of breast tissue (gynecomastia).

There are many causes of hypogonadism. These can be differentiated with hormone testing. Pituitary dysfunction is one cause of hypogonadism and can result from compression of the pituitary gland by a large pituitary tumor. In addition, excess hormone secretion by a pituitary tumor can cause hypogonadism either directly or indirectly. For example, elevated prolactin, cortisol or GH levels can suppress levels of FSH and LH, the pituitary hormones that stimulate estrogen production from the ovaries and testosterone production from the testes. Reproductive hormone levels normalize with treatment of the tumor in some, but not all, cases.

There are other causes of hypogonadism that are not related to pituitary tumors. These include disorders of the ovaries, testes, or hypothalamus. Additionally, amenorrhea can occur in the setting of malnutrition, such as that which occurs in anorexia nervosa, or with extreme exercise, which puts excessive nutritional and other demands on the body. Low testosterone can result from anabolic steroid use (for body building or athletic enhancement) and obesity.

The complications of hypogonadism include osteoporosis, infertility, sexual dysfunction, loss of muscle mass, depression and fatigue.

Hypogonadism is diagnosed when blood testing confirms low levels of estrogen or testosterone. Levels of FSH and LH are measured to determine whether the cause of hypogonadism is related to a pituitary disorder or another cause, such as ovarian or testicular failure. Other blood tests may be indicated to determine the cause, including measurement of prolactin levels and evaluation for Cushing's disease or acromegaly.

If the underlying cause of hypogonadism can be determined and corrected, then testosterone and estrogen levels often rise to normal levels. For example, medical treatment to lower prolactin levels from a prolactinoma often results in normalization of testosterone and estrogen levels. In addition, resection of large nonfunctioning pituitary tumors that are causing hypogonadism by compressing the pituitary gland results in restoration of normal reproductive hormones in approximately 50% of cases. Cure of acromegaly or Cushing's disease also often results in normalization of reproductive hormones.

In patients for whom the cause cannot be determined or addressed, testosterone replacement therapy or estrogen replacement therapy can be prescribed by an endocrinologist with expertise in this area. There are a number of different testosterone preparations available, including gels, solutions, and injections. Your endocrinologist can discuss the pros and cons of the different options with you and will also check lab tests to make sure it is safe to prescribe the medication. Women of reproductive age with amenorrhea (absent menstrual periods) can be prescribed estrogen in the form of oral contraceptive pills or low-dose patches, if they do not have contraindications to such therapy, and depending upon their specific needs. Assisted reproductive technologies are usually needed in such causes to achieve pregnancy. Decisions regarding estrogen replacement therapy in postmenopausal women should be made in consultation with an endocrinologist. If bone density does not improve with treatment of hypogonadism, then additional medications may be necessary to reduce the risk for fracture.