Kallmann syndrome is a form of hypogonadotrophic hypogonadism (HH).

Kallmann syndrome can be described as HH with an associated lack of sense of smell.

As far as diagnosis & treatment is concerned there is no difference between Kallmann syndrome and HH.

Hypogonadism is the condition where the gonads (testes in men, ovaries in women) stop functioning correctly and do not produce the hormones they normally do. This is a fairly common occurrence in older age, especially in men when testosterone levels can fall from middle age onwards.

Hypogonadotrophic hypogonadism (HH) is not the same condition and is a lot rarer than normal hypogonadism. Normally the testes & ovaries are controlled by hormones produced by a structure within the brain called the pituitary gland. These hormones are called gonadotrophins.

In HH the levels of gonadotrophins are so low as to prevent the testes & ovaries from functioning correctly.

In normal hypogonadism the testes & ovaries did function correctly at one stage.

In HH the testes & ovaries never had the chance to function correctly as they never had the correct gonadotrophin levels produced by the pituitary in order to perform correctly.


Gonadotrophins = hormones that act on the gonads (ovaries / testes)

Hypogonadism = under performance by the testes / ovaries

Hypogonadotrophic hypogonadism = under performance by the testes / ovaries due to low levels of gonadotrophins.

In Kallmann syndrome / HH the failure to enter puberty is due to the lack of gonadotrophin release by the pituitary gland which prevents the development of the testes / ovaries normally seen at puberty.