Hypogonadism occurs when there is a problem in the testes or a problem in the pituitary gland or the hypothalamus (which signal the testes to produce testosterone and sperm).
Symptoms vary depending at which age the testosterone deficiency begins.
The diagnosis is based on an examination, blood tests, and sometimes an analysis of the chromosomes.
Treatment depends on the cause but may include hormone therapy.
The pituitary gland secretes the hormones follicle-stimulating hormone and luteinizing hormone, which are called gonadotropins. These gonadotropins stimulate the male sex organs to produce the male sex hormone testosterone and the testes to produce sperm. When testosterone is lacking, growth and sexual development may be slow, sperm production is low, and the penis may be small.
Hypogonadism can occur while a fetus is developing in the womb or can occur during early or later childhood.
There are two basic types of hypogonadism:
Primary hypogonadism occurs when there is a problem in the testes.
Klinefelter syndrome occurs in about 1 in every 1,000 male births. It is caused by a chromosomal abnormality in which boys have two or more X chromosomes and one Y chromosome. Boys normally have one X and one Y. This syndrome is the most common cause of primary hypogonadism.
The testes are often small and firm and produce low amounts of testosterone. Boys tend to be tall with abnormally long arms and legs, may develop breast tissue (gynecomastia), and often have low muscle mass and less facial and body hair compared to other boys. Puberty (sexual maturity) may be absent, delayed, or incomplete.
The syndrome is usually first identified at puberty, when inadequate sexual development is noted, or later, when infertility is investigated.
In cryptorchidism (undescended testes), one or both of the testes remain in the abdomen. Usually the testes descend into the scrotum shortly before birth. At birth, about 3% of boys have undescended testes, but, in most of them, the testes spontaneously descend on their own within the first 4 months of life. The cause of cryptorchidism is usually unknown.
Vanishing testes syndrome (bilateral anorchia) occurs in about 1 in every 20,000 male births. The testes are likely present during early development in the womb but are resorbed by the body before or shortly after birth. Without testes, children cannot produce testosterone or sperm. Without testosterone or sperm, they cannot develop male secondary sexual characteristics (such as facial hair and muscle mass) and are infertile.
Absence of Leydig cells (cells in the testes that normally produce testosterone) leads to the development of partially developed genitals or ambiguous genitals. Ambiguous genitals are not clearly male or female. These defects develop because not enough testosterone is produced to stimulate the fetus to develop normal male genitals.
Noonan syndrome results in small testes that do not produce enough testosterone. This syndrome is caused by a genetic abnormality that may be inherited or occur early in a developing fetus. Children may have webbing of the neck, low-set ears, short stature, shortened fourth (ring) fingers, and heart and blood vessel abnormalities.
Secondary hypogonadism occurs when there is a problem in the pituitary gland or the hypothalamus (the part of the brain that controls the pituitary gland) that prevents the pituitary gland from secreting the hormones that stimulate the testes. Some of the causes involve genetic disorders that cause many other abnormalities.
Panhypopituitarism is a disorder that occurs when the pituitary gland stops or decreases producing hormones. This disorder can occur when the pituitary gland is damaged (such as by a tumor or an injury). Also see Hypopituitarism.
Laurence-Moon syndrome is a genetic disorder that causes obesity, intellectual disability, loss of vision, and extra fingers, toes, or both (polydactyly). Loss of vision occurs as the light-sensing structure at the back of the eye (the retina) gradually deteriorates (a disorder called retinitis pigmentosa).
Isolated luteinizing hormone deficiency occurs when only one pituitary hormone, luteinizing hormone, is missing. When luteinizing hormone is missing, the testes develop and produce sperm, because these functions are also controlled by follicle-stimulating hormone. However, the testes do not produce enough testosterone, so affected boys do not develop secondary sexual characteristics. Boys do continue to grow and may have abnormally long arms and legs.
Some children are normal but simply do not start puberty at the usual age, a phenomenon called constitutional delay of puberty. Children with constitutional delay of puberty are often referred to as late bloomers. Constitutional delay is more common among boys, and many children have a family history of delayed puberty in a parent or sibling.
Short stature is common during childhood and adolescence in children with constitutional delay, but at the expected time of puberty, growth often declines because the growth spurt that typically occurs at puberty is delayed. As a result, there is a noticeable difference in height between affected children and their peers during the early adolescent years. These children typically show signs of puberty by age 18 and ultimately reach a normal height and develop normally. However, the delay may cause anxiety.
Constitutional delay is not caused by hormonal or genetic problems or an underlying disorder (such as inflammatory bowel disease or eating disorders), but doctors may evaluate children to rule out other causes of short stature and delayed puberty.
Symptoms of hypogonadism vary depending at which age the testosterone deficiency begins.
In a male fetus, testosterone deficiency before the 12th week of pregnancy causes incomplete development of the genitals. The urethra may open on the underside of the penis instead of at its end. If testosterone deficiency develops later in pregnancy, a male fetus may have an abnormally small penis or testes that do not descend into the scrotum.
A male infant may have genitals that appear less masculine (undervirilized) or appear more female, sometimes referred to as ambiguous genitalia.
In male children, testosterone deficiency that occurs at the time when puberty is expected results in incomplete sexual development. An affected boy retains a high-pitched voice and has poor muscle development for his age. The penis, testes, and scrotum are underdeveloped. Pubic and underarm hair is sparse and body hair does not exist. The breasts may enlarge (gynecomastia), and the arms and legs are abnormally long.
Doctors suspect the diagnosis of hypogonadism when a boy has developmental abnormalities or delayed puberty. Doctors examine the boy's penis and testes to see whether they are normally developed for his age.
To confirm the diagnosis, doctors do blood tests to measure the levels of testosterone, luteinizing hormone, and follicle-stimulating hormone. The levels of luteinizing hormone and follicle-stimulating hormone help doctors determine whether hypogonadism is primary or secondary. Doctors measure levels of other hormones as well.
Doctors may do a chromosomal analysis, especially if they suspect Klinefelter syndrome. Chromosomes and genes can be evaluated by analyzing a sample of blood (see Testing for chromosome and gene abnormalities).
Various treatments are done depending on the cause of hypogonadism.
For cryptorchidism, doctors do surgery to move the undescended testes into the scrotum, which usually enables the testes to function normally. Surgical repair helps prevent future complications.
For secondary hypogonadism, doctors treat any underlying disorder of the pituitary gland or hypothalamus. Supplements of testosterone are given, and the dose is increased over a period of 18 to 24 months.
For testosterone deficiency, as in secondary hypogonadism, doctors give adolescents injections of testosterone every 2 to 4 weeks, and the dose is increased over a period of 18 to 24 months. Testosterone can also be delivered through a patch on the skin or as a gel.
For constitutional delay of puberty, doctors may give testosterone injections for 4 to 6 months. At low doses, testosterone starts puberty, causes the development of some masculine characteristics (virilization), and does not prevent adolescents from reaching their adult height potential.
Genetic disorders cannot be cured, but hormone therapy may help sexual characteristics develop.