title: Effect of hypothyroidism on the NO/cGMP pathway of corpus cavernosum in rabbits.
abstract: BACKGROUND
  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.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Faculty of Medicine, Uludag University, Bursa, Turkey. Electronic address: hkilicarslan@uludag.edu.tr.
authors.forename: Hakan
authors.initials: H
authors.lastname: Kilicarslan
authors.affiliation: Faculty of Medicine, Cumhuriyet University, Sivas, Turkey.
authors.forename: Ihsan
authors.initials: I
authors.lastname: Bagcivan
authors.affiliation: Faculty of Medicine, Cumhuriyet University, Sivas, Turkey.
authors.forename: M Kemal
authors.initials: MK
authors.lastname: Yildirim
authors.affiliation: Faculty of Medicine, Cumhuriyet University, Sivas, Turkey.
authors.forename: Bulent
authors.initials: B
authors.lastname: Sarac
authors.affiliation: Faculty of Medicine, Cumhuriyet University, Sivas, Turkey.
authors.forename: Tijen
authors.initials: T
authors.lastname: Kaya
mesh_terms: D000818:Animals; D002217:Carbachol / Q000008:administration & dosage; D006152:Cyclic GMP / Q000378:metabolism*; D004195:Disease Models, Animal; D004558:Electric Stimulation; D007037:Hypothyroidism / Q000150:complications* / Q000378:metabolism*; D018783:Impotence, Vasculogenic / Q000209:etiology* / Q000378:metabolism; D008297:Male; D009126:Muscle Relaxation / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism*; D009599:Nitroprusside / Q000008:administration & dosage; D010208:Papaverine / Q000008:administration & dosage; D010413:Penis / Q000378:metabolism*; D011817:Rabbits; D013965:Thyroidectomy; D014665:Vasodilator Agents / Q000008:administration & dosage
chemical_list: D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide; D002217:Carbachol; D010208:Papaverine; D006152:Cyclic GMP