Rare cases of oestrogen receptorα(ERα) deficiency have been described and the phenotype is very similar to that of aromatase deficiency with tall stature and eunucoid body proportions, continued linear growth into adulthood due to incomplete epiphyseal closure and osteoporosis in males [12] and absent breast development and markedly elevated serum oestrogen levels and multicystic ovaries in females [13]. This evidence concerns the gene CYP19A1 and hyperinsulinemic hypoglycemia, familial, 4.