She later underwent karyotyping, ACTH stimulation test and genetic analysis which revealed a 46,XX karyotype, no change in basal serum 17 hydroxyprogesterone level after ACTH administration, and CYP17A1 gene mutation, respectively, thereby effectively diagnosing her as a case of 17‐alpha‐hydroxylase deficiency. This evidence concerns the gene CYP17A1 and hyperinsulinemic hypoglycemia, familial, 4.