The Effect of 5-Alpha Reductase on Testosterone in Men

2014-07-23 21:52:15 | BioPortfolio


The enzyme 5-alpha reductase is present in small amounts in muscle and converts testosterone to dihydrotestosterone (DHT). Testosterone affects lean body tissue, muscle size, muscle strength, and sexual function in men. This study will evaluate how 5-alpha reductase influences the effects of testosterone in young healthy men.


Testosterone, the predominant circulating androgen in men, serves as the active hormone in some target tissues; however, testosterone effects in other target organs require its conversion to two active metabolites, estradiol 17-beta and DHT. The role of 5-alpha reductase in mediating testosterone's effects on muscle and sexual function remains unclear. This study will determine whether 5-alpha reduction of testosterone to DHT is necessary for mediating effects on fat-free mass, muscle size, muscle strength, and leg power in men. The study will also evaluate the necessity of 5-alpha reductase for maintenance of androgen effects on sexual function (sexual desire, overall sexual activity, nocturnal penile tumescence [NPT], response to visual erotic stimulus, and penile rigidity) in men.

Participants in this study will be treated with a drug to suppress endogenous testosterone production. Participants will then be randomly assigned to receive either testosterone and placebo or testosterone and the 5-alpha reductase inhibitor dutasteride. Testosterone will be administered weekly; dutasteride and placebo will both be administered daily. Diet and exercise will be standardized across both groups. Participants will be assessed at study entry and Week 20. Assessments will include measurements such as a DEXA scan, MRI scan, and muscle performance and sexual function tests. Participants will also have blood tests for safety monitoring; blood tests will include measures of hematocrit, liver enzymes (AST and ALT), prostate specific antigen (PSA), and cholesterol.

Study Design

Allocation: Randomized, Control: Placebo Control, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double-Blind, Primary Purpose: Treatment


Sex Disorders


testosterone enanthate, duastride


Charles R. Drew University
Los Angeles
United States




Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)

Results (where available)

View Results


Published on BioPortfolio: 2014-07-23T21:52:15-0400

Clinical Trials [400 Associated Clinical Trials listed on BioPortfolio]

Subcutaneous Testosterone Enanthate Safety in Adult Men Diagnosed With Hypogonadism

Evaluation of the safety and tolerability of testosterone enanthate (TE) following a single dose via QuickShot® Testosterone (QST) 50 mg, 75 mg, or 100 mg when administered by intended us...

Oral Androgens in Man-4: (Short Title: Oral T-4)

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 addit...

Pharmacokinetic Study of Oral Testosterone (T) Ester Formulations in Hypogonadal Men

The purpose of this pharmacokinetic study is to determine whether oral testosterone ester formulations can be used effectively to treat men with low testosterone.

5-Alpha Reductase and Anabolic Effects of Testosterone

The purpose of this study is to determine whether a higher-than-replacement dose of testosterone and finasteride can be combined to safely increase muscle strength in older men who have a ...

Study to Determine the Effects of Testosterone Replacement Therapy in Aging Men With Androgen Deficiency

The T-001 study is a placebo-controlled investigation of the effects of injectable testosterone replacement therapy on prostate tissues of aging men with low testosterone levels. The prim...

PubMed Articles [5986 Associated PubMed Articles listed on BioPortfolio]

Amount of Testosterone on Laundered Clothing After Use of Testosterone Topical 2% Solution by Healthy Male Volunteers.

Testosterone 2% solution (Axiron) applied to armpit(s) is used for replacement therapy in men with a deficiency of endogenous testosterone.

Longitudinal Changes Over 10 Years in Free Testosterone Among HIV-Infected and HIV-Uninfected Men.

Aging in males is associated with lower testosterone levels and a decrease in diurnal variation of testosterone secretion. Cross-sectional studies have shown lower than expected testosterone levels am...

Effects of long term administration of testosterone and estradiol on spatial memory in rats.

There are many discrepancies around the effect of sex hormones on spatial learning and memory in rodents. The aim of the present study was to investigate the effects of chronic administration of estra...

Effects of Testosterone Treatment in Older Men.

Background Serum testosterone concentrations decrease as men age, but benefits of raising testosterone levels in older men have not been established. Methods We assigned 790 men 65 years of age or old...

Imbalance in the diurnal salivary testosterone/cortisol ratio in men with severe obstructive sleep apnea: an observational study.

The complex relationship between sleep disorders and hormones could lead to alterations in the production of cortisol and testosterone in obstructive sleep apnea (OSA) patients.

Medical and Biotech [MESH] Definitions

Steroidal compounds related to TESTOSTERONE, the major mammalian male sex hormone. Testosterone congeners include important testosterone precursors in the biosynthetic pathways, metabolites, derivatives, and synthetic steroids with androgenic activities.

A potent androgenic metabolite of TESTOSTERONE. Dihydrotestosterone (DHT) is generated by a 5-alpha reduction of testosterone. Unlike testosterone, DHT cannot be aromatized to ESTRADIOL therefore DHT is considered a pure androgenic steroid.

A potent androgenic steroid and major product secreted by the LEYDIG CELLS of the TESTIS. Its production is stimulated by LUTEINIZING HORMONE from the PITUITARY GLAND. In turn, testosterone exerts feedback control of the pituitary LH and FSH secretion. Depending on the tissues, testosterone can be further converted to DIHYDROTESTOSTERONE or ESTRADIOL.

An ester of TESTOSTERONE with a propionate substitution at the 17-beta position.

A progesterone that has been used in ESTRUS SYNCHRONIZATION and has been evaluated as an injectable contraceptive in combination with estradiol enanthate. It is also used therapeutically as a topical anti-inflammatory and is applied topically in the treatment of ACNE.

More From BioPortfolio on "The Effect of 5-Alpha Reductase on Testosterone in Men"

Quick Search

Relevant Topics

Enzymes are proteins that catalyze (i.e., increase the rates of) chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical re...

Arthritis Fibromyalgia Gout Lupus Rheumatic Rheumatology is the medical specialty concerned with the diagnosis and management of disease involving joints, tendons, muscles, ligaments and associated structures (Oxford Medical Diction...

Diabetes Diabetes Endocrine Obesity Oxycontin Renal Disease Thyroid Disorders Endocrinology is the study of the endocrine glands and the hormones that they secrete (Oxford Medical Dictionary). There are several groups of h...

Searches Linking to this Trial