LEP and cartilage-hair hypoplasia: Thus, unlike neurosensory hearing loss or anosmia, metabolic defects are not typically considered as primary events in CHH, apart from syndromic CHH caused by LEP, LEPR, or PCSK1 mutations resulting in both GnRH deficiency and morbid obesity (Jackson et al, 1997; Farooqi et al, 2002, 2007).