An Experimental Approach to the Interrelationship Between Hyperthyroidism and Ejaculation Latency Time in Male Rats Ahmet Cihan,* Nergis Murat, Omer Demir, Guven Aslan, Tevfik Demir, Sedef Gidener and Ahmet Adil Esen From the Departments of Urology (AC, OD, GA, AAE), Internal Medicine (Section of Endocrinology) (TD) and Pharmacology (SG), Dokuz Eylul University School of Medicine and Dokuz Eylul University Health Service Institute (NM), Izmir, Turkey Purpose: We investigated the effects of experimentally induced hyperthyroidism on seminal vesicle pressure measurements and bulbospongiosus muscle contrac- tile activity in a para-chloroamphetamine (Sigma-Aldrich®) induced ejaculation model in rats. Materials and Methods: Male Wistar rats were used in the study. Daily injection of 25 g/100 gm body weight L-thyroxine (T4, Sigma-Aldrich) for 14 days was performed in 14 rats to induce hyperthyroidism. Seven L-thyroxine injected rats were in the hyperthyroid group. The remaining 7 rats (recovery group) under- went operation after a 28-day washout period to determine spontaneous recovery from hyperthyroidism. At each operation seminal vesicle catheterization was done to measure intraluminal pressure and bulbospongiosus muscle dissection was performed for electromyography. After intraperitoneal administration of 5 mg/kg para-chloroamphetamine physiological parameters related to the ejacula- tory process were measured. Results: The interval between para-chloroamphetamine administration and first ejaculation was significantly decreased in the hyperthyroid rat group compared with that in the control group (mean  SD 202.8  22.3 vs 465.4  104.6 seconds, p = 0.001). Seminal vesicle phasic contraction frequency was significantly higher than control group values in hyperthyroid rats (for 30 min- utes 32.3  13.9, p = 0.047). The mean AUC of bulbospongiosus muscle electro- myography activity was also significantly increased in this group (11.1  4.1 V per second  10 -4 ,p = 0.0001). All parameters in recovery and control group rats were not significantly differed from each other. Conclusions: Hyperthyroidism leads to enhanced seminal vesicle contraction frequency and bulbospongiosus muscle contractile activity in rats. Hyperthyroid- ism affects the emission and expulsion phases of ejaculation in reversible fashion. Key Words: testis; seminal vesicles; hyperthyroidism; ejaculation; rats, Wistar Abbreviations and Acronyms ATPase = adenosine triphosphatase BS = bulbospongiosus EMG = electromyography LSt = lateral spinothalamic PCA = para-chloroamphetamine PE = premature ejaculation SV = seminal vesicle TSH = thyroid stimulating hormone Submitted for publication May 3, 2008. Study received approval from the local ethics committee on the use of laboratory animals for experimental research. * Correspondence: Department of Urology, Dokuz Eylul University School of Medicine, P. O. Box: 35340, Inciralti, Izmir, Turkey (telephone: 90 0506 231 73 54; FAX: 90 0232 259 23 17; e-mail: ahmet.cihan@deu.edu.tr). IN the wide spectrum of sexual dysfunc- tions PE has a large place. 1 Current theories to explain the exact etiopathol- ogy of PE are based on psychological or biological mechanisms. 2 Although these mechanisms are indistinguishable from each other, physicians generally prefer to find an obvious underlying cause of diseases to be able to treat them easily. Thus, trials that have focused on other possible physiopathological mechanisms to determine a reversible biological risk factor for PE have caused great interest. Recently some clinical evi- dence has supported the notion that hyperthyroidism is a potential etio- 0022-5347/09/1812-0907/0 Vol. 181, 907-912, February 2009 THE JOURNAL OF UROLOGY ® Printed in U.S.A. Copyright © 2009 by AMERICAN UROLOGICAL ASSOCIATION DOI:10.1016/j.juro.2008.10.061 www.jurology.com 907