PLOD1 and hypogonadism: Therefore, obesity induces a suppression of the hypothalamus–pituitary–gonadal axis (22, 24), representing one of the leading causes of secondary hypogonadism in men (23) with a biochemical picture characterised by normal or low concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and reduced serum testosterone concentrations (22–24).