The bones and the brain are two important tissues in humans where the primary effect of testosterone is by way of aromatization to estradiol. In the bones, estradiol accelerates ossification of cartilage into bone, leading to closure of the epiphyses and conclusion of growth. In the central nervous system, testosterone is aromatized to estradiol. Estradiol rather than testosterone serves as the most important feedback signal to the hypothalamus (especially affecting LH secretion).[115] In many mammals, prenatal or perinatal "masculinization" of the sexually dimorphic areas of the brain by estradiol derived from testosterone programs later male sexual behavior.[116]
^ David KG, Dingemanse E, Freud JL (May 1935). "Über krystallinisches mannliches Hormon aus Hoden (Testosteron) wirksamer als aus harn oder aus Cholesterin bereitetes Androsteron" [On crystalline male hormone from testicles (testosterone) effective as from urine or from cholesterol]. Hoppe-Seyler's Z Physiol Chem (in German). 233 (5–6): 281–83. doi:10.1515/bchm2.1935.233.5-6.281.
The unsexy truth is that increasing T naturally simply comes down to making some long-term changes in your diet and lifestyle. As you’ll see, what I did to increase T largely boils down to eating better, exercising smarter, and getting more sleep. That’s pretty much it. But as with most things in life, the devil is in the details, so I’ll share with you exactly what I did and provide research that explains why the things I did helped boost my testosterone.
Present in much greater levels in men than women, testosterone initiates the development of the male internal and external reproductive organs during foetal development and is essential for the production of sperm in adult life. This hormone also signals the body to make new blood cells, ensures that muscles and bones stay strong during and after puberty and enhances libido both in men and women. Testosterone is linked to many of the changes seen in boys during puberty (including an increase in height, body and pubic hair growth, enlargement of the penis, testes and prostate gland, and changes in sexual and aggressive behaviour). It also regulates the secretion of luteinising hormone and follicle stimulating hormone. To effect these changes, testosterone is often converted into another androgen called dihydrotestosterone. 

Xenoestrogen is a chemical that imitates estrogen in the human body. When men are exposed to too much of this estrogen-imitating chemical, T levels drop significantly. The problem is xenoestrogen is freaking everywhere — plastics, shampoos, gasoline, cows, toothpaste. You name it and chances are there are xenoestrogen in it. The ubiquitous nature of this chemical in our modern world is one reason some endocrinologists believe that testosterone levels are lower in men today than in decades past. It’s also a reason doctors say the number of boys born with hypospadias — a birth defect in which the opening of the urethra is on the underside of the penis and not at the tip — has doubled.  Note to expecting parents: make sure mom stays away from xenoestrogens during the pregnancy.

Most studies support a link between adult criminality and testosterone, although the relationship is modest if examined separately for each sex. Nearly all studies of juvenile delinquency and testosterone are not significant. Most studies have also found testosterone to be associated with behaviors or personality traits linked with criminality such as antisocial behavior and alcoholism. Many studies have also been done on the relationship between more general aggressive behavior/feelings and testosterone. About half the studies have found a relationship and about half no relationship.[66]
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   Article Courtesy of Better Nutrition  
Smith and colleagues (2005) undertook a prospective study on the contribution of stress to coronary heart disease. Their study, which involved 2512 men aged 45 to 59 years, looked at a number of metabolic parameters. They found that an increased cortisol to testosterone ratio was associated with a high risk of coronary artery disease and that this risk was mediated by components of the insulin resistance syndrome. They reported that high cortisol and low testosterone levels are associated with a worsening of insulin resistance and that there is evidence to support the possibility of improving this pattern by treatment with testosterone.
When you’re under stress (be it from lack of sleep, workplace stress, emotional stress, stress from a bad diet, overtraining etc.), your body releases cortisol. Cortisol blunts the effects of testosterone (47), which makes sense from an evolutionary point of view – if we were stressed as cavemen chances are it was a life or death situation – not running late to a meeting - in this state (i.e. running from a lion) the body wouldn’t care if you couldn’t get it up, there was more to worry about!
That testosterone decreases with age has been clearly established by many studies over many years in several different populations of men (Harman et al 2001; Feldman et al 2002; Araujo et al 2004; Kaufman and Vermeulen 2005). Of even greater significance is the steeper fall of the most biologically active fraction of total testosterone, non-sex hormone binding globulin (SHBG)- bound testosterone, or bioavailable testosterone (bio-T). The classical, but not the only approach to measuring bio-T, is to precipitate out SHBG (and hence the testosterone which is strongly bound to it as well) and measure the remainder as total testosterone (Tremblay 2003). Vermeulen et al (1999) have devised a less tedious and less expensive method of measuring a surrogate for bio-T, namely calculated bio-T, inserting total T, albumin, SHBG and a constant into a mathematical formulation. There is a strong correlation between actual bio-T and calculated bio-T (Emadi-Konjin et al 2003).

If you're a man who's experiencing symptoms such as decreased sex drive, erectile dysfunction, depressed mood, and difficulties with concentration and memory, and you think low testosterone may be to blame, you can have your levels tested. Since testosterone levels fluctuate throughout the day, you'll probably need more than a blood test to get a true picture of your levels.

Nearly 1 out of every 4 men over age 50 experience the pain of losing the ability to perform sexually as a result of erectile dysfunction (ED). Common causes of ED are atherosclerosis, diabetes, prescription drug use (namely high blood pressure, depression, and allergy drugs), and—you guessed it—low testosterone. Supplements that may help include the following:
The science backs up the soldier’s self discovery, in fact, exposure to radiation (whether it’s from an army radar or the cell phone in your pocket, or the wifi router in your house) has been shown to lower sperm quality, fertility and testosterone. This is true not only for military personnel (88, 89,90) but all males living in a modern world (91). provides accurate and independent information on more than 24,000 prescription drugs, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. Data sources include IBM Watson Micromedex (updated 1 Mar 2019), Cerner Multum™ (updated 1 Mar 2019), Wolters Kluwer™ (updated 28 Feb 2019) and others. Refer to our editorial policy for content sources and attributions.
Hoffman, J., Ratamess, N., Kang, J., Magine, G., Faigenbaum, A. & Stout, J. (2006, August). Effect of creatine and beta-alanine supplementation on performance and endocrine responses in strength/power athletes [Abstract]. International Journal of Sport Nutrition and Exercise Metabolism, 16(4), 430–46. Retrieved from
^ Jump up to: a b Lazaridis I, Charalampopoulos I, Alexaki VI, Avlonitis N, Pediaditakis I, Efstathopoulos P, Calogeropoulou T, Castanas E, Gravanis A (2011). "Neurosteroid dehydroepiandrosterone interacts with nerve growth factor (NGF) receptors, preventing neuronal apoptosis". PLoS Biol. 9 (4): e1001051. doi:10.1371/journal.pbio.1001051. PMC 3082517. PMID 21541365.
Two of the immediate metabolites of testosterone, 5α-DHT and estradiol, are biologically important and can be formed both in the liver and in extrahepatic tissues.[151] Approximately 5 to 7% of testosterone is converted by 5α-reductase into 5α-DHT, with circulating levels of 5α-DHT about 10% of those of testosterone, and approximately 0.3% of testosterone is converted into estradiol by aromatase.[2][151][157][158] 5α-Reductase is highly expressed in the male reproductive organs (including the prostate gland, seminal vesicles, and epididymides),[159] skin, hair follicles, and brain[160] and aromatase is highly expressed in adipose tissue, bone, and the brain.[161][162] As much as 90% of testosterone is converted into 5α-DHT in so-called androgenic tissues with high 5α-reductase expression,[152] and due to the several-fold greater potency of 5α-DHT as an AR agonist relative to testosterone,[163] it has been estimated that the effects of testosterone are potentiated 2- to 3-fold in such tissues.[164]
Testosterone is a stimulant of hematopoiesis in the bone marrow and consequently, increases the hematocrit (Shahidi 1973). Men with unexplained anemia should have their testosterone measured and if reduced, these men should be treated with testosterone. Because of the erythropoietin stimulating effect of testosterone, one of the parameters to be monitored during testosterone treatment is hematocrit since a small percent of testosterone-treated men develop polycythemia.
If your levels are indeed low, there are a number of synthetic and bioidentical testosterone products on the market, as well as DHEA, which is the most abundant androgen precursor prohormone in the human body, meaning that it is the largest raw material your body uses to produce other vital hormones, including testosterone in men and estrogen in women.
Great article with a lot of useful information. I completely agree with your top three picks. I have done a ton of research as well. Currently I am taking Testogen for over two months and it has worked for me. It has double my low T and I am 61 years old. I do feel better and have more energy. Even have morning wood sometimes and haven’t for a long time.
In order to discuss the biochemical diagnosis of hypogonadism it is necessary to outline the usual carriage of testosterone in the blood. Total serum testosterone consists of free testosterone (2%–3%), testosterone bound to sex hormone binding globulin (SHBG) (45%) and testosterone bound to other proteins (mainly albumin −50%) (Dunn et al 1981). Testosterone binds only loosely to albumin and so this testosterone as well as free testosterone is available to tissues and is termed bioavailable testosterone. Testosterone bound to SHBG is tightly bound and is biologically inactive. Bioavailable and free testosterone are known to correlate better than total testosterone with clinical sequelae of androgenization such as bone mineral density and muscle strength (Khosla et al 1998; Roy et al 2002). There is diurnal variation in serum testosterone levels with peak levels seen in the morning following sleep, which can be maintained into the seventh decade (Diver et al 2003). Samples should always be taken in the morning before 11 am to allow for standardization.
A large number of side-effects have been attributed to testosterone. In our clinical experience, the incidence of significant adverse effects with treatment producing physiological testosterone levels is low, and many side effects attributed to testosterone are mainly relevant to supraphysiological replacement. Some adverse effects are specific to a given mode of delivery and have already been described. Potential adverse effects concerning the prostate have also been discussed and require appropriate monitoring of symptoms, PSA and digital rectal examination. Other tumors which may be androgen responsive include cancer of the breast and primary liver tumors, and these are both contraindications to testosterone treatment
Low testosterone levels can cause mood disturbances, increased body fat, loss of muscle tone, inadequate erections and poor sexual performance, osteoporosis, difficulty with concentration, memory loss and sleep difficulties. Current research suggests that this effect occurs in only a minority (about 2%) of ageing men. However, there is a lot of research currently in progress to find out more about the effects of testosterone in older men and also whether the use of testosterone replacement therapy would have any benefits.
Millions of American men use a prescription testosterone gel or injection to restore normal levels of the manly hormone. The ongoing pharmaceutical marketing blitz promises that treating "low T" this way can make men feel more alert, energetic, mentally sharp, and sexually functional. However, legitimate safety concerns linger. For example, some older men on testosterone could face higher cardiac risks.