In addition to conjugation and the 17-ketosteroid pathway, testosterone can also be hydroxylated and oxidized in the liver by cytochrome P450 enzymes, including CYP3A4, CYP3A5, CYP2C9, CYP2C19, and CYP2D6.[155] 6β-Hydroxylation and to a lesser extent 16β-hydroxylation are the major transformations.[155] The 6β-hydroxylation of testosterone is catalyzed mainly by CYP3A4 and to a lesser extent CYP3A5 and is responsible for 75 to 80% of cytochrome P450-mediated testosterone metabolism.[155] In addition to 6β- and 16β-hydroxytestosterone, 1β-, 2α/β-, 11β-, and 15β-hydroxytestosterone are also formed as minor metabolites.[155][156] Certain cytochrome P450 enzymes such as CYP2C9 and CYP2C19 can also oxidize testosterone at the C17 position to form androstenedione.[155]
Ashwagandha is sometimes included in testosterone supplements because of the hypothesis that it improves fertility. However, we couldn’t find sufficient evidence to support this claim (at best, one study found that ashwagandha might improve cardiorespiratory endurance). WebMD advocates caution when taking this herb, as it may interact with immunosuppressants, sedative medications, and thyroid hormone medications.
Acne and Allergic Reactions: The testosterone is universally regarded as one of the triggering factors for acne. It stimulates the activity of oil glands making the skin more oily and vulnerable to acne. This body hormone might also cause allergic reactions, such as hives, rash, difficulty breathing, itching, chest tightness, and big swelling of the facial parts.
Levels of testosterone naturally decrease with age, but exactly what level constitutes "low T," or hypogonadism, is controversial, Harvard Medical School said. Testosterone levels vary wildly, and can even differ depending on the time of day they're measured (levels tend to be lower in the evenings). The National Institutes of Health includes the following as possible symptoms of low testosterone:
Michael T. Murray, ND, is widely regarded as one of the leading authorities on natural medicine. He is the author of many books, including the classic Encyclopedia of Nutritional Supplements. His latest book is What the Drug Companies Won’t Tell You and Your Doctor Doesn’t Know. Visit him online at doctormurray.com.   Article Courtesy of Better Nutrition  
Conflicting results have been obtained concerning the importance of testosterone in maintaining cardiovascular health.[29][30] Nevertheless, maintaining normal testosterone levels in elderly men has been shown to improve many parameters that are thought to reduce cardiovascular disease risk, such as increased lean body mass, decreased visceral fat mass, decreased total cholesterol, and glycemic control.[31]
Although some men believe that taking testosterone medications may help them feel younger and more vigorous as they age, few rigorous studies have examined testosterone therapy in men who have healthy testosterone levels. And some small studies have revealed mixed results. For example, in one study healthy men who took testosterone medications increased muscle mass but didn't gain strength.
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