Information About Kallmann Syndrome

When Your Hypothalamus Is Unable to Work Properly

Man having an MRI
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Kallmann syndrome affects men more often than women, affecting approximately 1 in 8,000 to 10,000 males and 1 in 40,000 to 70,000 females worldwide.

Kallmann syndrome may be inherited or may occur in someone with no family history of the disorder. The most common inherited form is the ​X-linked form. The KAL1 gene on the X chromosome is responsible for this form. The next most common inherited form is due to a mutation in the KAL2 gene on chromosome 8. It is inherited in an autosomal dominant way. The third inherited form of Kallmann syndrome is due to the mutation of the KAL3 gene and is inherited as an autosomal recessive disorder. The exact location of the KAL3 gene has not yet been discovered.


In Kallmann syndrome, a part of the brain, the hypothalamus, is unable to work properly. This causes symptoms including:

  • failure to go through puberty
  • no sense of smell (anosmia) or very weak ability to smell (hyposmia)
  • undescended testes (cryptorchidism) in males
  • a small penis (microphallus) in males
  • menstruation never starts in women (called primary amenorrhea)
  • simultaneous movement of both hands (called bimanual synkinesis) affects about one-fifth of males with the disorder

There are other symptoms that occur less often, such as being born with only one kidney or having osteoporosis (weak bones).


If someone fails to go through puberty, he or she is referred to an endocrinologist for diagnosis and care. This type of doctor specializes in hormone disorders and can determine exactly why puberty did not occur.

There are many reasons why someone might not go through puberty. However, Kallmann syndrome is the only one associated with no ability to smell. It is usually easy to determine if Kallmann syndrome may be present by performing a smell test.

There are two types of smell tests. One uses small bottles that have different substances in them; the other test uses "scratch and sniff" cards. Both tests use substances that have strong smells that most everyone knows, such as coffee. If the person being tested has a normal sense of smell, then another disorder besides Kallmann syndrome is present.

A physical examination will show whether undescended testes or small genitals are present in a male. A family history of Kallmann syndrome would be an important clue to diagnosis. A blood test is done to measure the levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as testosterone or estrogen. All these hormones are important for normal sexual development. Very low levels of these hormones mean there is a problem with either the hypothalamus or the pituitary gland in the brain.

In Kallmann syndrome, the lack of a sense of smell is due to the absence of structures called olfactory bulbs in the brain. A magnetic resonance imaging (MRI) scan of the head can show whether these structures are present or not.


Treatment of Kallmann syndrome focuses on replacing the hormones that are missing. For men, either testosterone or hCG is given by injection on a schedule. For women, estradiol pills are taken daily. Progesterone tablets are also taken daily for the last 14 days of each month to create a menstrual cycle. An alternative to taking two types of tablets is using contraceptive pills that contain both estrogen and progesterone. For both men and women, other treatments are available for infertility. Proper treatment of individuals with Kallmann syndrome allows them to achieve normal reproductive health.

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