A logical question that follows is, what happens to endogenous levels of Arhgap39/Porf-2 when insulin or IGF-1 is deficient as in type 1 diabetes or growth hormone deficiency, either congenital (Laron syndrome) or age-related (Gong et al., 2014), or if the response to insulin or IGF-1 is blocked, as seen in obesity with insulin resistance, type 2 diabetes, or aging (Bentov et al., 2014)? The gene discussed is IGF1; the disease is obesity due to melanocortin 4 receptor deficiency.