Kallman's syndrome describes the occurrence of hypothalamic gonadotrophin releasing hormone deficiency and deficient olfactory sense - hyposmia or anosmia. It is usually inherited as an X-linked or autosomal recessive disorder with greater penetrance in the male. However, new mutations may arise.
Gonadotrophin deficiency arises from a failure of embryonic migration of GnRH secreting neurons from their site of origin in the nose. The same defect affects the olfactory neurones resulting in olfactory bulb aplasia.
More than half of patients have associated somatic stigmata, most commonly, nerve deafness, colour blindness, mid-line cranio-facial deformities such as cleft palate or harelip, and renal abnormalities. Most are of normal or above average stature. Females may present with primary amenorrhoea; males with cryptorchidism.
Deficient olfactation can be demonstrated using simple stimuli such as cloves, peppermint and eucalyptus. Serum LH and FSH are low.
Exogenous sex steroid should be given to induce and maintain secondary sexual characteristics. Since the underlying defect is at the hypothalamic level, achievement of fertility may require pulsatile GnRH. This is administered by means of a pump worn 24 hourly. However, the pumps are expensive, available only in specialist centres and often perceived as a nuisance. Alternative therapy with exogenous gonadotrophins in the form of hCG or as human menopausal gonadotrophin which contains both FSH and LH may be tried.
About 50% of treated patients may achieve pregnancies.