IGFBP3 and hyperinsulinemic hypoglycemia, familial, 4: We expect D3 to have low toxicity based on (1) no weight loss or deaths in D3-treated mice compared to controls; (2) the health and fertility of IGFBP-3 overexpressing transgenic mice57; and (3) approval of a recombinant IGFBP3 and IGF1 complex (mecasermin rinfabate) for IGF1 deficiency in children58.