SI deficiencies can be categorized as (a) primary or congenital SI deficiencies which are caused by genetic alterations in the SI gene and are already present at birth and (b) induced or secondary SI deficiencies which occur later in life and are mediated by environmental factors or arise as a consequence of other genetic deficiencies which negatively influence the intestinal physiology in general and SI function in particular. This evidence concerns the gene SI and hyperinsulinemic hypoglycemia, familial, 4.