GnRH is first produced in the area of the primitive nose and migrates to the area of the basal hypothalamus by twenty weeks of gestation.
This process may be impaired by genetic factors: for example, a foetus with Kallmann's syndrome (isolated gonadotrophin deficiency and anosmia) demonstrated altered nasal development and absence of immunostainable GnRH in the basal medial and basal hypothalamus at twenty weeks of gestation, a time when normal male foetuses have ample GnRH in these areas.
