VDR and obesity due to melanocortin 4 receptor deficiency: Taking into account that low 25(OH)D plasma level are known to be associated with obesity and that the activation of the vitamin D receptor inhibits IgE production and 25(OH)D influences specific the IgE response, we tested the hypothesis that circulating 25(OH)D concentrations are negatively related to circulating allergen-specific IgE concentrations distinctly in an adult population-based study cohort (29).