Hypogonadism is the condition in which the production of sex hormones and germ cells are inadequate. It is more prevalent in males than in females.

The gonads are the organs of sexual differentiation--in the female, they areovaries; in the male, the testes. Along with producing eggs and sperm, they produce sex hormones that generate all the differences between men and women.If they produce too little sex hormone, then either the growth or the function of the sexual organs is impaired.

The gonads are not independent in their function, however. They are loosely controlled by the pituitary gland. The pituitary hormones are the same for males and females, but the gonadal hormones are different. Men produce mostly androgens, and women produce mostly estrogens. These two kinds of hormones regulate the development of the embryo and direct the adolescent maturation of sex organs into their adult form. Further, they sustain those organs andtheir function throughout the reproductive years. The effects of estrogen reach beyond that to sustain bone strength and protect the cardiovascular system from degenerative disease.

Hormones can be inadequate during or after each stage of development--embryonic and adolescent. During each stage, inadequate hormone stimulation will prevent normal development. After each stage, a decrease in hormone stimulationwill result in failed function and perhaps some shrinkage. The organs affected principally by sex hormones are the male and female genitals, and the female breasts. Body hair, fat deposition, bone and muscle growth, and some brainfunctions are also influenced.

Sex is determined at the moment of conception by the sex chromosomes, one ofeach of which is provided by the parent. A female receives two X chromosomes,one from her mother and one from her father. A male receives an X from his mother (the only kind she has to give) and a Y chromosome from his father. Genetic defects sometimes result in changes in the chromosomes. If sex chromosomes are involved, there is a change in the development of sexual characteristics.

Female is the default sex of the embryo, so most of the sex organ deficits atbirth occur in boys. Some, but not all, are due to inadequate androgen stimulation. The penis may be small, the testicles undescended (cryptorchidism) orvarious degrees of "feminization" of the genitals may be present.

After birth, sexual development does not occur until puberty. Hypogonadism most often shows up as an abnormality in boys during puberty. Again, notevery defect is due to inadequate hormones. Some are due to too much of thewrong hormone. Kallmann's syndrome is a birth defect in the brain that prevents release of hormones and appears as failure of male puberty. Some boys havean adequate amount of androgen in their system but fail to respond to it, acondition known as androgen resistance.

Female problems in puberty or with the reproductive system are rarelyrelated to a lack of hormones, but rather to complex rhythms gone wrong. Women's problems with too little hormone happen during menopause, which isa normal hypogonadism.

A number of adverse events can damage the gonads and result in decreased hormone levels. The childhood mumps, if acquired after puberty, can infectand destroy the testicles--a disease called viral orchitis. Ionizing radiation and chemotherapy, trauma, several drugs (spironolactone, a diuretic and ketoconazole, an antifungal agent), alcohol, marijuana, heroin, methadone, and environmental toxins can all damage testicles and decrease their hormone production. Severe diseases in the liver or kidneys, certain infections, sickle-cell anemia, and some cancers also affect gonads.To treat some male cancers, it is necessary to remove the testicles, therebypreventing the androgens from stimulating cancer growth. This procedure, still called castration or orchiectomy, removes androgen stimulation fromthe whole body.

For several reasons the pituitary can fail. It happens rarely after pregnancy. It used to be removed to treat advanced breast or prostate cancer. Sometimes the pituitary develops a tumor that destroys it. Failure of the pituitary is called hypopituitarism and, of course, leaves the gonads with no stimulation to produce hormones.

Besides the tissue changes generated by hormone stimulation, the only other symptoms relate to sexual desire and function. Libido is enhanced by testosterone, and male sexual performance requires androgens. The role of female hormones in female sexual activity is less clear, although hormones strengthen tissues and promote healthy secretions, facilitating sexual activity.

Currently, there are accurate blood tests for most of the hormones in the body, including those from the pituitary and even some from the hypothalamus. Chromosomes can be analyzed, and gonads can be, but rarely are, biopsied.

Replacing missing body chemicals is much easier than suppressing excesses. Estrogen replacement is recommended for nearly all women after menopause for its many beneficial effects. Estrogen can be taken by mouth, injection, or skinpatch. It is strongly recommended that the other female hormone, progesterone, be taken as well, because it prevents overgrowth of uterine lining and uterine cancer. Testosterone replacement is available for males who are deficient.

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