Kallmann Syndrome Definition and Characterization

Defining Kallmann Syndrome

The pituitary gland, highlighted in green.
The pituitary gland, highlighted in green.. BSIP/UIG/Getty Images

Kallmann syndrome is a rare genetic condition that causes delayed or absent puberty and an impaired sense of smell. It is also a form of hypogonadotropic hypogonadism, a condition that affects the production of hormones involved in sexual development. This syndrome affects males more often than females, because it is often X-linked, and symptoms vary widely. Researchers have identified four different types of Kallman syndrome, each with a distinct genetic cause.

In Our Own Words

Kallmann syndrome is a rare genetic disorder that is characterized by abnormal development and delayed puberty. Individuals typically cannot smell, and are unable to normally produce hormones involved in sexual development.

Symptoms can also include things like a cleft lip and cleft palate, being born with only one kidney, hearing loss, abnormal eye movements, or a condition in which voluntary movement in one part of the body triggers an involuntary movement in another part--for instance, one hand mirrors the other hand’s movements.

Interestingly, about ten percent of individuals with Kallmann syndrome regain their hormonal functioning on their own, for unknown reasons. Typically, however, this congenital disorder is treated with hormone replacement therapy.

More Information About Kallmann Syndrome

The two main features of Kallmann syndrome are hypogonadic hypogonadism and anosmia.

The term hypogonadic hypogonadism means that the pituitary gland in the brain doesn't produce gonadotropin-releasing hormone (GnRH). This hormone stimulates the gonads, or testes and ovaries, which in turn release steroid hormones that enable sexual maturation. Thus, people with Kallmann syndrome fail to mature sexually unless they receive gonadal steroidal hormone therapy, or sex hormones.

The reason why people with Kallmann syndrome exhibit anosmia or the inability to smell is because the GnRH neurons or nerve cells are located within the olfactory (smell) system, and both areas are messed up during development.

Boys with Kallmann syndrome have a small penis (micropenis) and undescended testes (cryptorchidism). Typically, these boys fail to sexually mature, grow facial hair and the voice doesn't deepen. Sometimes, boys with this condition exhibit very limited sexual maturation.

Girls with Kallmann syndrome can't menstruate and have limited or no breast development.

Interestingly, people with Kallmann syndrome often don't know that they can't smell, or are anosmic, until they are tested for this sense. Of note, lack of smell distinguishes Kallmann syndrome from other forms of hypogonadic hypogonadism.

Kallmann syndrome is rare and affects one person per 10,000 to 86,000 people.

There are 4 types of Kallmann syndrome, with type 1 being most common. People with type 1 and type 2 Kallmann syndrome also exhibit cleft palate.

Kallmann syndrome is congenital, or present from birth, and is developmental in scope. In addition to lack of sexual maturation and improper olfactory development, other developmental symptoms of Kallmann syndrome can include the following:

  • failure of one kidney to develop
  • failure of teeth to develop
  • abnormal eye movements
  • failure of the lip and mouth to develop (cleft lip with or without cleft palate)
  • bimanual synkinesis, or abnormal hand movements, which may impair a person's ability to play a musical instrument

Synonyms: Idiopathic hypogonadotropic hypogonadism, Congenital hypogonadotropic hypogonadism

Medical Specialties: Endocrinology, Medical genetics, Pediatrics


National Institutes of Health. Genetics Home Reference. Accessed August 2013.

National Organization for Rare Disorders. Accessed August 2013.

Kallman Syndrome blog. “Kallman Syndrome and Anosmia." July 7, 2013. Accessed Sept. 2013.

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