Kallmann Syndrome

Kallmann syndrome is a genetic condition which results in the failure to commence or the non-completion of puberty. It is characterised by hypogonadism and by a total lack of sense of smell (anosmia) or a heavily reduced sense of smell (hyposmia). The term hypogonadism describes a low level of circulating sex related hormones; (testosterone in men and oestrogen and progesterone in women).

It is part of a family of conditions that come under the term hypogonadotropic hypogonadism (HH). The condition can also be known as congenital hypogonadotrophic hypogonadism (CHH), isolated hypogonadotropic hypogonadism (IHH), hypothalamic hypogonadism or familial hypogonadism. The additonal phrase "with anosmia" is used to indicate if a normal sense of smell is absent.

Kallmann syndrome is a specific form of isolated hypogonadotropic hypogonadism where there is an associated lack of sense of smell. Approximately 50% of HH cases occur with no sense of smell and are termed as Kallmann Syndrome. There is no distinction between Kallmann syndrome and other forms of HH in terms of diagnosis and treatment, apart from the fact that Kallmann syndrome is associated with the lack of sense of smell.

Abnormalities in various genes have be shown to disrupt the ability of the hypothalamus to produce gonadotrophin releasing hormone GnRH which in turn causes the pituitary to fail to release sufficient levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). LH and FSH have a direct action on the testes in men and ovaries in women.

The term hypogonadotropic hypogonadism (HH) reflects the disease mechanism. The term "hypo" means below or under. Hypogonadism means a low level of circulating sex hormones, testosterone for the men and oestrogen and progesterone for the women. Hypogonadotropic means low levels of the gonadotropin hormones, LH and FSH, normally secreted by the anterior pituitary gland under the influence of GnRH.

The term HH indicates a condition where there are low levels of testosterone or oestrogen and progesterone caused by low levels of FSH and LH. Overall Kallmann syndrome and other forms of HH cause a disruption in the communication pathway between the hypothalamus, pituitary and the testes or ovaries. The end result can be a failure to start or complete puberty, infertility and low levels of testosterone in men or oestrogen and progesterone in women.

Kallmann syndrome was described in 1944 by Franz Josef Kallmann, a German-American geneticist. However, others, such as the Spanish doctor Aureliano Maestre de San Juan in 1856, had noticed a correlation between anosmia and hypogonadism.

The condition has a low prevalence, estimated at 1 in 4,000 for male HH cases overall and 1:10,000 for Kallmann syndrome. It is three to five times more common in males than females.

The best-known person who has Kallmann syndrome is the jazz vocalist Jimmy Scott. In 2004, Canadian writer Brian Brett published a memoir, Uproar's Your Only Music, about growing up with Kallmann syndrome.