The protocol was designed to address the hypothesis that oral testosterone enanthate plus dutasteride can suppress the secretion of LH and FSH after four weeks of administration. In addition, we will compare the gonadotropin suppression mediated by a dose of testosterone enanthate (400 mg twice daily) that would be expected to maintain the serum testosterone in the normal range throughout the day, with the same dose (800 mg once daily) administered once daily. This larger once-daily dose is expected to result in a higher peak and lower trough by the end of the dosing interval

This study will be carried out in a double-blinded fashion, so neither the subject nor the investigator will be aware of treatment assignment during the study. This protocol is designed to address the hypothesis that oral testosterone enanthate plus dutasteride can suppress the secretion of LH and FSH after four weeks of administration. In addition, we will compare the gonadotropin suppression mediated by a dose of testosterone enanthate (400 mg twice daily) that would be expected to maintain the serum testosterone in the normal range throughout the day, with the same dose (800 mg once daily) administered once daily. This larger once-daily dose is expected to result in a higher peak and lower trough by the end of the dosing interval. Secondary endpoints in this study include the ability of oral testosterone enanthate plus dutasteride to maintain short-term androgen-mediated endpoints such as mood and sexual function over the 4-week treatment period as well as weekly measures of safety, including blood counts, PSA and liver and kidney function.

• Drug: Testosterone Enanthate
• Drug: Dutasteride
• Other: placebo sesame oil

• Active Comparator: Oral Testosterone enanthate in sesame oil, 400 mg po (orally), BID (twice daily) + dutasteride 0.5 mg orally, qd (once daily) for 28 days + dutasteride load 24.5 mg po once
• Active Comparator: Oral Testosterone sesame oil, 800 mg po (orally), qd (in am daily) + placebo sesame oil (in pm daily) + dutasteride 0.5 mg orally, qd (once daily) for 28 days + dutasteride load 24.5 mg po once

• Amory JK, Kalhorn TF, Page ST. Pharmacokinetics and Pharmacodynamics of Oral Testosterone Enanthate Plus Dutasteride for Four Weeks in Normal Men: Implications for Male Hormonal Contraception. J Androl. 2007 Nov 28; [Epub ahead of print]
• Martin CW, Anderson RA, Cheng L, Ho PC, van der Spuy Z, Smith KB, Glasier AF, Everington D, Baird DT. Potential impact of hormonal male contraception: cross-cultural implications for development of novel preparations. Hum Reprod. 2000 Mar;15(3):637-45.
• Weston GC, Schlipalius ML, Bhuinneain MN, Vollenhoven BJ. Will Australian men use male hormonal contraception? A survey of a postpartum population. Med J Aust. 2002 Mar 4;176(5):208-10.
• Heinemann K, Saad F, Wiesemes M, White S, Heinemann L. Attitudes toward male fertility control: results of a multinational survey on four continents. Hum Reprod. 2005 Feb;20(2):549-56. Epub 2004 Dec 17.
• Amory JK, Bremner WJ. Oral testosterone in oil plus dutasteride in men: a pharmacokinetic study. J Clin Endocrinol Metab. 2005 May;90(5):2610-7. Epub 2005 Feb 15.
• Amory JK, Page ST, Bremner WJ. Oral testosterone in oil: pharmacokinetic effects of 5alpha reduction by finasteride or dutasteride and food intake in men. J Androl. 2006 Jan-Feb;27(1):72-8.
• Bebb RA, Anawalt BD, Christensen RB, Paulsen CA, Bremner WJ, Matsumoto AM. Combined administration of levonorgestrel and testosterone induces more rapid and effective suppression of spermatogenesis than testosterone alone: a promising male contraceptive approach. J Clin Endocrinol Metab. 1996 Feb;81(2):757-62.
• Anawalt BD, Bebb RA, Bremner WJ, Matsumoto AM. A lower dosage levonorgestrel and testosterone combination effectively suppresses spermatogenesis and circulating gonadotropin levels with fewer metabolic effects than higher dosage combinations. J Androl. 1999 May-Jun;20(3):407-14.
• Anawalt BD, Amory JK, Herbst KL, Coviello AD, Page ST, Bremner WJ, Matsumoto AM. Intramuscular testosterone enanthate plus very low dosage oral levonorgestrel suppresses spermatogenesis without causing weight gain in normal young men: a randomized clinical trial. J Androl. 2005 May-Jun;26(3):405-13.

Inclusion Criteria:

• Males between 18 to 55 years of age
• In good general health based on normal screening evaluation (consisting of a medical history, physical exam, normal serum chemistry, hematology, and baseline hormone levels)
• Subject must agree not to participate in another research drug study for the duration of the study
• Subject must agree to not donate blood during the study
• Subject must be willing to comply with the study protocol and procedures

Exclusion Criteria:

• Men in poor general health, with abnormal blood results (clinical laboratory tests or hormone values)
• A known history of alcohol or drug abuse
• A history of testicular disease or severe testicular trauma,
• A history of bleeding disorders or current use of anti-coagulants
• A history of sleep apnea and/or major psychiatric disorders
• A body-mass index greater than 35,
• A history of or current use of testosterone
• Infertility