ANGPTL8 and obesity due to melanocortin 4 receptor deficiency: These studies show that betatrophin levels were altered in various physiologic conditions, such as the postprandial state [26], and pathological conditions, such as type 2 diabetes [26–30], type 1 diabetes [30, 31], and obesity [26, 29], and were associated with metabolic parameters, such as BMI [26, 29], glucose [26, 28], and insulin resistance [28, 29].