CRP and obesity due to melanocortin 4 receptor deficiency: Large-scale epidemiological studies have associated obesity and systemic inflammation (e.g., elevated C-reactive protein (CRP)) with lower testosterone levels [62,63,64], whereas the administration of proinflammatory cytokines or endotoxins to men [65] or the treatment of Leydig cells in culture with proinflammatory cytokines have been shown to decrease testosterone production [66].