Effect of hypothyroidism on the NO/cGMP pathway of corpus cavernosum in rabbits.

Author(s): Kilicarslan H, Bagcivan I, Yildirim MK, Sarac B, Kaya T

Affiliation(s): Department of Urology, Faculty of Medicine, Uludag University, Bursa, Turkey. hkilicarslan@uludag.edu.tr

Publication date & source: 2006-09, J Sex Med., 3(5):830-7.

Publication type: Comparative Study

INTRODUCTION: The incidence of hormonal dysfunction as a cause of impotence remains controversial. However, several recent studies have reported evidence of hormonal abnormalities in 25-35% of impotent men. Hypothyroidism has been reported to occur in 6% of impotent men. There is some evidence suggesting that hypothyroidism may be a cause of impotence. AIM: We aimed to investigate the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway in hypothyroidism in an experimental rabbit model and compared hypothyroid rabbits with controls to evaluate the possible involvement of the NO/cGMP pathway. METHODS: The study comprised 20 male New Zealand white rabbits. The rabbits were divided into two equal groups. The first group had hypothyroidism induced surgically by thyroidectomy for 6 weeks. The second group underwent a sham operation. RESULTS: There was no significant change in the mean body weight of hypothyroid rabbits and controls. Triiodothyronine and thyroxine levels were significantly lower in hypothyroid rabbits. Plasma thyroid-stimulating hormone and prolactin levels were significantly higher in hypothyroid rabbits. Plasma total calcium and parathormone levels remained in the normal range in both groups. MAIN OUTCOME MEASURES: Papaverine-induced concentration-dependent relaxations were similar in both groups. Carbachol-induced relaxation responses decreased in hypothyroid rabbits. There were significant differences between control and hypothyroid rabbits in frequency-dependent relaxations induced by electrical-field stimulation (EFS). YC-1-induced relaxation responses did not change significantly in hypothyroid rabbits. Concentration-dependent relaxations induced by diethylamine (DEA)/NO were similar in both groups. Amrinone-induced relaxation responses did not change significantly in hypothyroid rabbits. CONCLUSION: Reductions of relaxant responses to EFS and carbachol in hypothyroid rabbits can depend on the decrease of released or synthesized NO from nitrergic nerves and endothelium.