This book demonstrated that post-pubertal hypothyroidism in male rats was associated with hyperhomocysteinemia, oxidative stress and other biochemical alterations. These factors may, at least in part, contribute toward testicular dysfunction, which eventually leads to the testicular degenerative biochemistry and morphology. Indeed, this postulates an indirect negative impact of post-pubertal hypothyroidism on testicular function through development of these factors. This is plus the observed role of folic acid supplementation in enhancing spermatogenesis and building up the antioxidant status against the oxidants.