Both testosterone and 5α-DHT are metabolized mainly in the liver.[1][151] Approximately 50% of testosterone is metabolized via conjugation into testosterone glucuronide and to a lesser extent testosterone sulfate by glucuronosyltransferases and sulfotransferases, respectively.[1] An additional 40% of testosterone is metabolized in equal proportions into the 17-ketosteroids androsterone and etiocholanolone via the combined actions of 5α- and 5β-reductases, 3α-hydroxysteroid dehydrogenase, and 17β-HSD, in that order.[1][151][152] Androsterone and etiocholanolone are then glucuronidated and to a lesser extent sulfated similarly to testosterone.[1][151] The conjugates of testosterone and its hepatic metabolites are released from the liver into circulation and excreted in the urine and bile.[1][151][152] Only a small fraction (2%) of testosterone is excreted unchanged in the urine.[151]
Currently available testosterone preparations in common use include intramuscular injections, subcutaneous pellets, buccal tablets, transdermal gels and patches (see Table 2). Oral testosterone is not widely used. Unmodified testosterone taken orally is largely subject to first-pass metabolism by the liver. Oral doses 100 fold greater than physiological testosterone production can be given to achieve adequate serum levels. Methyl testosterone esters have been associated with hepatotoxicity. There has been some use of testosterone undecanoate, which is an esterified derivative of testosterone that is absorbed via the lymphatic system and bypasses the liver. Unfortunately, it produces unpredictable testosterone levels and increases testosterone levels for only a short period after each oral dose (Schurmeyer et al 1983).
Your first step should be to see your doctor. If you think you have low testosterone, we cannot stress enough that you should proceed with caution and talk to a medical professional — taking a booster can definitely do more harm than good. Low testosterone can be a symptom of more serious problems, like a pituitary disorder or a side-effect of medication, and a booster can mask the root cause. A doctor will be able to evaluate your testosterone levels with a simple blood test, and if you both decide a booster is the way to go, give the ingredients of any supplement a once-over to make sure that they’re not at risk of making your personal health situation worse.
A number of research groups have tried to further define the relationship of testosterone and body composition by artificial alteration of testosterone levels in eugonadal populations. Induction of a hypogonadal state in healthy men (Mauras et al 1998) or men with prostate cancer (Smith et al 2001) using a gonadotrophin-releasing-hormone (GnRH) analogue was shown to produce increases in fat mass and decreased fat free mass. Another experimental approach in healthy men featured suppression of endogenous testosterone production with a GnRH analogue, followed by treatment with different doses of weekly intramuscular testosterone esters for 20 weeks. Initially the experiments involved men aged 18–35 years (Bhasin et al 2001) but subsequently the study was repeated with a similar protocol in men aged 60–75 years (Bhasin et al 2005). The different doses given were shown to produce a range of serum concentrations from subphysiological to supraphysiological (Bhasin et al 2001). A given testosterone dose produced higher serum concentrations of testosterone in the older age group (Bhasin et al 2005). Subphysiological dosing of testosterone produced a gain in fat mass and loss of fat free mass during the study. There were sequential decreases in fat mass and increases in fat free mass with each increase of testosterone dose. These changes in body composition were seen in physiological and supraphysiological treatment doses. The trend was similar in younger versus older men but the gain of fat mass at the lowest testosterone dose was less prominent in older patients (Bhasin et al 2001; Bhasin et al 2005). With regard to muscle function, the investigators showed dose dependent increases in leg strength and power with testosterone treatment in young and older men but there was no improvement in fatigability (Storer et al 2003; Bhasin et al 2005).
I am also suspect of the fact that men 100 years ago had testosterone levels of 800-2000 ng/dL. The truth is that there are men today that are stronger and more muscular than the men from 100 years ago. Sure the “average man” of today is less than the “average man” of prior generations, but this is because we sit around in offices all day, and then come home to sit on the couch and watch tv…little to no activity.

You’re probably most familiar with testosterone as being the sex hormone responsible for defining “manhood.” And, yes, it does. However, proper levels of this key hormone are also necessary to stimulate sexual desire, increase libido, heighten arousal and ensure sexual satisfaction for both men and women. It’s also necessary to maintaining the following:
Dobs and colleagues found that men with an increased body mass index had both reduced testosterone and reduced high density lipoprotein (HDL) levels. Treatment with testosterone increased the levels of HDL (Dobs et al 2001). Rising levels of HDL are not a consistent finding with TRT. More often, however, one finds reduced total cholesterol, low density lipoprotein (LDL) cholesterol and triglyceride levels with TRT (Zgliczynski et al 1996; Whitsel et al 2001).
The prevalence of biochemical testosterone deficiency increases with age. This is partly due to decreasing testosterone levels associated with illness or debility but there is also convincing epidemiological data to show that serum free and total testosterone levels also fall with normal aging (Harman et al 2001; Feldman et al 2002). The symptoms of aging include tiredness, lack of energy, reduced strength, frailty, loss of libido, decreased sexual performance depression and mood change. Men with hypogonadism experience similar symptoms. This raises the question of whether some symptoms of aging could be due to relative androgen deficiency. On the other hand, similarities between normal aging and the symptoms of mild androgen deficiency make the clinical diagnosis of hypogonadism in aging men more challenging.
An international consensus document was recently published and provides guidance on the diagnosis, treatment and monitoring of late-onset hypogonadism (LOH) in men. The diagnosis of LOH requires biochemical and clinical components. Controversy in defining the clinical syndrome continues due to the high prevalence of hypogonadal symptoms in the aging male population and the non-specific nature of these symptoms. Further controversy surrounds setting a lower limit of normal testosterone, the limitations of the commonly available total testosterone result in assessing some patients and the unavailability of reliable measures of bioavailable or free testosterone for general clinical use. As with any clinical intervention testosterone treatment should be judged on a balance of risk versus benefit. The traditional benefits of testosterone on sexual function, mood, strength and quality of life remain the primary goals of treatment but possible beneficial effects on other parameters such as bone density, obesity, insulin resistance and angina are emerging and will be reviewed. Potential concerns regarding the effects of testosterone on prostate disease, aggression and polycythaemia will also be addressed. The options available for treatment have increased in recent years with the availability of a number of testosterone preparations which can reliably produce physiological serum concentrations.
In summary, low testosterone levels are linked to the presence of numerous cardiovascular risk factors. Testosterone treatment acts to improve some of these factors, but effects may vary according to pre- and post-treatment testosterone levels, as well as other factors. There is little data from trials specific to aging males. Appropriately-powered randomized controlled trials, with cardiovascular disease primary endpoints, are needed to clarify the situation, but in the meantime the balance of evidence is that testosterone has either neutral or beneficial effects on the risk of cardiovascular disease in men. It is particularly important to define the effect of testosterone treatment on cardiovascular disease in view of its potential use as an anti-anginal agent.

Testosterone is a vital hormone for men, but just like estrogen in women, it goes down as you age. This is a natural process that has many drawbacks. In men, testosterone is responsible for hair growth, bone density, proper weight distribution, sex drive, muscle mass, red cell production, and so much more. But did you know that you can actually increase your testosterone levels as opposed to letting them dwindle?

As “the ultimate guide” I want this article to be the last resource you need when it comes to boosting your testosterone. I have spent years researching this stuff, and experimenting on myself. And in case I am incomplete, I have linked out at the bottom of this page to all the best resources for increasing testosterone around the web. I truly believe there is no better resource out there than what you’re reading right now.
The regulation of testosterone production is tightly controlled to maintain normal levels in blood, although levels are usually highest in the morning and fall after that. The hypothalamus and the pituitary gland are important in controlling the amount of testosterone produced by the testes. In response to gonadotrophin-releasing hormone from the hypothalamus, the pituitary gland produces luteinising hormone which travels in the bloodstream to the gonads and stimulates the production and release of testosterone.
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