Kallmann syndrome causes hypogonadotropic hypogonadism, a condition where the ovaries or testes do not produce enough sex hormones. It also causes an impaired sense of smell. The syndrome is present from birth and is rare, with one study indicating that it affects one in 48,000. Kallmann syndrome affects males more than females, with only one in 125,000 females having the condition compared to one in 30,000 males.
Kallmann syndrome results from the underdevelopment of specific nerves in the brain. These nerves signal the hypothalamus to release gonadotropin-releasing hormone. Normally, this hormone signals the pituitary gland to release sex hormones. In Kallmann syndrome, there is either too little gonadotropin-releasing hormone or none at all, so the pituitary gland does not receive the proper signal.
During fetal development, the part of the hypothalamus that produces gonadotropin-releasing hormone develops as a part of the nose. The underdeveloped nerves that cause Kallmann syndrome also affect the sense of smell. If a gonadotropin-releasing hormone deficiency occurs in someone with a normal sense of smell, then they do not have Kallmann syndrome.
Most people with Kallmann syndrome do not have a family history of the condition, but people with the disease can pass it on to their offspring in various ways, depending on the gene that's involved. The inheritance pattern can be autosomal-recessive, where each parent is a carrier; autosomal-dominant, where one parent passes on the gene; or X-linked, where the mother is the carrier. In the latter, the mother can pass the condition on to her son, but a father cannot. Daughters can become carriers by inheriting the gene from either parent.
Males with Kallmann syndrome may have some signs in infancy, like a small penis or undescended testes. Most cases are undiagnosed until puberty when a lack of sexual development becomes evident. Males with Kallmann syndrome typically do not grow facial or body hair and may have delayed growth spurts.
Females with Kallmann syndrome have stunted growth spurts, decreased pubic hair growth, and no breast development. Some do not experience menses, while others may begin menstruating at a normal age and stop after a few cycles. Females with Kallmann syndrome may also go through partial puberty that fails to progress.
Other symptoms of Kallmann syndrome appear in both males and females. They include a cleft lip or palate, short fingers and toes, development of a single kidney, color blindness, abnormal eye movements, hearing loss, abnormal teeth, and mirror hand movements, where one hand unconsciously mirrors the movement of the other.
If left untreated, symptoms can evolve and worsen as the person matures into adulthood. Men can experience decreased muscle mass and bone loss, low sex drive, infertility, and erectile dysfunction. Women with Kallmann syndrome who do not receive treatment usually have no periods and may experience little to no breast development.
Diagnosis usually begins with a physical exam and a health history. The doctor asks questions about symptoms with delayed puberty and any impairments with the sense of smell. As Kallmann syndrome is often inherited, the doctor also looks for any relatives that have had issues with fertility or delayed puberty.
If the doctor suspects Kallmann syndrome, they may request lab work to determine hormone levels or genetic testing to look for certain gene mutations. An MRI may also help determine if there are any anatomical abnormalities in the brain.
The treatment for Kallmann syndrome is hormone replacement therapy. Initial treatment focuses on inducing puberty, while later treatment may shift to focus on fertility. Depending on the severity of symptoms, people with Kallmann syndrome may also need medication to promote bone health.
Some people with the condition need ongoing hormone replacement, though, in one small study, 10 to 15 percent of males began to produce normal hormone levels in the long term.
Kallmann syndrome is not fatal and is not associated with decreased life expectancy. A small subset of people with Kallmann syndrome may experience other health issues, like osteoporosis and congenital heart defects, which may decrease their quality of life or shorten life expectancy. Fertility is also an issue for adults with Kallmann syndrome, though it is achievable in most cases.
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