5-a reductase is an enzyme that converts testosterone into the more androgenic DHT, increasing the steroid’s effect on sex glands, skin and hair. Prostate enlargement and hair loss are directly related to DHT; these conditions are treated with drugs that block the actions of 5-a reductase, such as finasteride (Propecia, Proscar) and duasteride (Avodart).39,40 Another site where the 5-a reductase is present in high concentration is in the brain. DHT is believed to be responsible for many of the psychotropic properties of testosterone (aggression, focus, libido). Additionally, DHT, like estrogen, is involved in testosterone feedback regulation. By blocking 5-a reductase at the hypothalamus, there would be less negative feedback, allowing testosterone levels to be maintained at a higher level. Generally, 5-a reductase inhibition leads to a 15 – 20% increase in serum testosterone or roughly 3 nmol.41 This slight increase is unlikely to result in an anabolic effect. In fact, 5-a reductase inhibition may be ergolytic, as many patients using the drugs for hair loss or prostatic hypertrophy report sexual dysfunction, loss of aggression/focus and gynecomastia. Reducing DHT (by approximately 90%) affects the androgenic : estrogenic balance, increasing the risk for feminizing side effects.41,42

    The minimal increase in testosterone and associated side effects make the use of 5-a reductase inhibitors an inappropriate choice for an anabolic advantage, with the possible exception of using such drugs concurrently with an anti-estrogen. Even then, adverse side effects may arise that would negate any benefit.

    Anabolic steroids are not the only means of increasing serum testosterone. hCG, anti-estrogens and 5-a reductase inhibitors have all been reported to increase testosterone; some into the supraphysiologic range. While the combined effects of two or more of these class of drugs have not been reported in the literature, anecdotal reports and their use in anti-aging regimens suggest that the combination of hCG and aromatase inhibitors are being used successfully by practitioners. It is important for those who are considering the use of these drugs to realize they will have a mild to moderate effect on testosterone and muscle growth. Further, the doses of all drugs should be moderated to avoid fluctuations in estrogen or DHT. Proper dosing will require blood tests and monitoring.

    These methods are less effective methods at raising testosterone levels or promoting muscle growth than the use of anabolic steroids provide, but they are options that make use of natural testosterone production by maximizing stimulation and minimizing feedback inhibition. hCG and anti-estrogens are effective enough to warrant their placement on the banned substance list by WADA; they are also commonly used in many clinical situations. The long term safety and effectiveness of these agents, particularly in men with impaired testicular function remain unknown. As there are centers offering the use of these agents, soliciting the direction of an experienced physician may be crucial to maximizing benefits while avoiding any potential pitfalls or side effects.

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