Despite the differences in etiology and pathogenesis of reproductive dysfunctions in T1DM and aging, the main causes of androgen deficiency and impaired spermatogenesis are the reduced T production by Leydig cells due to an increase in oxidative stress, inflammation and apoptosis in the testes, as well as the hormonal dysregulation due to an imbalance between signaling cascades regulated by gonadotropins, insulin, insulin-like growth factor-1 and adipokines in testicular cells [28,38,63]. The gene discussed is IGF1; the disease is type 1 diabetes mellitus.