LEP and obesity due to melanocortin 4 receptor deficiency: Compared to non-carriers in the lowest quintile of leptin, carriers of the obesity risk A allele in the highest quintile had a substantially increased risk of colorectal cancer (multivariate adjusted OR = 2.55; 95% CI, 1.21–5.39), although the interaction was not statistically significant (Pinteraction = 0.30).