LEP and Obesity: Numerous studies have reported a significant correlation between the levels of leptin, obesity, and infertility with respect to the hypothalamic–pituitary–testicular axis, decreases in serum testosterone and sperm parameters, and increases in follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels, as well as abnormal sperm morphology [11,13,15,37,40].