We demonstrate herein that hypothyroidism in male rats increased the hypothalamic expression of prodynorphin and compromised testicular Kiss1/Kiss1r expression, whereas the administration of Kp10 not only reversed the high PRL levels caused by hypothyroidism but also improved the gonadal axis, sperm morphology, and testicular expression of Kiss1 and Kiss1r. Here, PDYN is linked to hypothyroidism.