CYP17 causes hypocortisolism in the South African Angora goat

Two cytochrome P450 17alpha-hydroxylase/17,20-lyase (CYP17) isoforms have been identified in the South African Angora goat (Capra hircus) and have been implicated as the primary cause of hypocortisolism in this subspecies. These goats are the most efficient fibre producing, but least hardy, small stock breed in Southern Africa. Their inability to cope with prolonged exposure to cold and the resulting stock loss which occurs during winter have been the subject of numerous studies. The two isoforms are encoded for by two separate genes, a novel finding for a mammalian species. The enzymes have unique catalytic properties and differ with respect to their 17,20-lyase activities towards 17-hydroxypregnenolone and subsequent androgen production. In vivo assays confirmed that the three resulting genotypes differed in their ability to produce cortisol in response to intravenous insulin injection implicating CYP17 as the primary cause of the observed hypocortisolism.