PCSK1 and obesity due to melanocortin 4 receptor deficiency: We assessed the effect of common variants in PCSK1, notably the rs6232 and rs6235 polymorphisms on BMI variation and obesity risk in a total of 8,359 Americans from two multi-ethnic studies: the Coronary Artery Risk Development in Young Adults (CARDIA) study and the Multi-Ethnic Study of Atherosclerosis (MESA).