More severe POR mutations cause the ABS phenotype, but mutations retaining ∼20% to 40% of activity may cause disturbed steroidogenesis without ABS (37), this may be considered “nonclassic POR deficiency.” The roles of these mutations in clinical disease, drug metabolism, and POR transcriptional regulation have been reviewed elsewhere (15, 16, 38) and will not be discussed here. The gene discussed is POR; the disease is hyperinsulinemic hypoglycemia, familial, 4.