INS and hyperinsulinism: As we show below, the three most common forms of hypoglycemia in newborn infants are all caused by altered regulation of pancreatic beta-cell insulin secretion: (1) transitional hypoglycemia in normal newborns (hereafter termed Transitional HI), (2) prolonged neonatal hyperinsulinism in high-risk neonates (hereafter termed Perinatal Stress-Induced HI), and (3) congenital genetic forms of hyperinsulinism (hereafter termed Genetic HI).