No funding was obtained for this study.

The purpose of this investigational drug study is to determine how much male hormone, testosterone, is needed to maintain sperm production in the testis.

This is a nine-month research study examining the effects on androgen treatment on sperm production in healthy men. There are three phase to the study, a 2-month screening phase, 4-month treatment and 3-month follow-up. In this study, the investigators aim to define a quantitative relationship between intra-testicular testosterone (IT-T) and spermatogenesis in man. Hormone levels will be measured in a small amount of testicular fluid at the beginning and end of treatment and sperm concentration will be measured.

Inclusion Criteria:

• Males age 18-55
• In general good health based on normal screening evaluation
• Normal serum testosterone, lutenizing hormone (LH) and follicle stimulating hormone (FSH)
• Prostate Specific Antigen (PSA) < 3.0
• Agrees not to donate blood or participate in another research study during the study
• Informed consent
• Must be willing to use a reliable form of contraception during the study

Exclusion Criteria:

• Participation in a long-term male contraceptive study within the past three months
• History of testosterone or anabolic steroid abuse in the past
• History of or current skin disorder that will interfere with testosterone gel
• Poor general health or significantly abnormal screening blood results
• History of or current testicular or prostate disease
• History of a bleeding disorder or need for anticoagulation
• History of untreated sleep apnea and/or major psychiatric problems
• BMI > 32
• History of or current liver disease
• Chronic pain syndrome
• Current use of terfenidine, astemizole, cisapride, budesonide, felodipine, fluticasone, lovastatin, midazolam, sildenafil, or vardenafil
• Use of glucocorticoids or underlying adrenal insufficiency
• Active drug or alcohol abuse within the past year