Puberty occurs when there is an “awakening” of the hypothalamic-pituitary axis. The hypothalamus increases its secretion of gonadotropin releasing hormone (GnRH) which in turn stimulates the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH). This leads to a significant increase in the production of testicular testosterone and the induction of the well-known secondary sex characteristics associated with puberty: growth spurt, increased libido, increased erectile function, acne, increased body hair, increased muscle mass, deepening of the voice, spermatogenesis, gynecomastia (usually transient).
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.
Free shipping available with any purchase over $49. No cash value. Void where prohibited, taxed or restricted by law. Valid at GNC.com or when calling 1-877-GNC-4700. Free shipping offer applies to ground shipping on orders shipped within the continental United States only. Free shipping offer does not include P.O. Boxes and APO/FPO addresses. Free shipping offer does not apply when shipping to Alaska, Hawaii or Puerto Rico. Not valid on previous purchases, exchanges or special orders. No substitutions or backorders. GNC may offer other free shipping offers periodically. Details of these offers will be set forth within the specific promotions. Free shipping offer excludes ready-to-drink products.
When testosterone and endorphins in ejaculated semen meet the cervical wall after sexual intercourse, females receive a spike in testosterone, endorphin, and oxytocin levels, and males after orgasm during copulation experience an increase in endorphins and a marked increase in oxytocin levels. This adds to the hospitable physiological environment in the female internal reproductive tract for conceiving, and later for nurturing the conceptus in the pre-embryonic stages, and stimulates feelings of love, desire, and paternal care in the male (this is the only time male oxytocin levels rival a female's).[citation needed]

^ Jump up to: a b Travison TG, Vesper HW, Orwoll E, Wu F, Kaufman JM, Wang Y, Lapauw B, Fiers T, Matsumoto AM, Bhasin S (April 2017). "Harmonized Reference Ranges for Circulating Testosterone Levels in Men of Four Cohort Studies in the United States and Europe". The Journal of Clinical Endocrinology and Metabolism. 102 (4): 1161–1173. doi:10.1210/jc.2016-2935. PMC 5460736. PMID 28324103.
The changes in average serum testosterone levels with aging mean that the proportion of men fulfilling a biochemically defined diagnosis of hypogonadism increases with aging. Twenty percent of men aged over 60 have total testosterone levels below the normal range and the figure rises to 50% in those aged over 80. The figures concerning free testosterone are even higher as would be expected in view of the concurrent decrease in SHBG levels (Harman et al 2001).

Anabolic–androgenic steroids (AASs) are synthetic derivatives of testosterone that are commonly used among athletes aged 18–40 years, but many reports have demonstrated the presence of numerous toxic and hormonal effects as a result of long-term use of an AAS.[9] Testosterone-foods act as natural libido boosters. Due to the growing interest in herbal ingredients and other dietary supplements worldwide, the use of testosterone boosters is becoming more and more mainstream among athletes, but several side effects were documented. Hence, this study established to help in the assessment of the side effects and health risks which could occur among athletes consuming testosterone boosters.
During the second trimester, androgen level is associated with sex formation.[13] This period affects the femininization or masculinization of the fetus and can be a better predictor of feminine or masculine behaviours such as sex typed behaviour than an adult's own levels. A mother's testosterone level during pregnancy is correlated with her daughter's sex-typical behavior as an adult, and the correlation is even stronger than with the daughter's own adult testosterone level.[14]
Phthalates are found to cause poor testosterone synthesis by disrupting an enzyme required to create the male hormone. Women with high levels of DEHP and DBP (two types of phthalates) in their system during pregnancy were found to have sons that had feminine characteristics Phthalates are found in vinyl flooring, detergents, automotive plastics, soaps and shampoos, deodorants, perfumes, hair sprays, plastic bags and food packaging, among a long list of common products. Aside from phthalates, other chemicals that possess gender-bending traits are:
Studies conducted in rats have indicated that their degree of sexual arousal is sensitive to reductions in testosterone. When testosterone-deprived rats were given medium levels of testosterone, their sexual behaviors (copulation, partner preference, etc.) resumed, but not when given low amounts of the same hormone. Therefore, these mammals may provide a model for studying clinical populations among humans suffering from sexual arousal deficits such as hypoactive sexual desire disorder.[37]
Testosterone may prove to be an effective treatment in female sexual arousal disorders,[52] and is available as a dermal patch. There is no FDA approved androgen preparation for the treatment of androgen insufficiency; however, it has been used off-label to treat low libido and sexual dysfunction in older women. Testosterone may be a treatment for postmenopausal women as long as they are effectively estrogenized.[52]
Intracoronary artery infusion of testosterone causes significant coronary artery dilatation and not constriction as previously thought (Webb et al 1999). When degree of coronary obstruction is assessed by angiography, there is a direct relationship between degree of coronary artery narrowing and reduced testosterone levels (Phillips et al 1994). Men with low testosterone levels have been observed to have: premature atherosclerosis, increased visceral adipose tissue, hyperinsulinemia, and other risk factors for myocardial infarction (Phillips 2005). Insulin resistance has been shown to be associated with a decrease in Leydig cell secretion of testosterone (Pitteloud et al 2005). Muller and colleagues suggest that low endogenous total testosterone and SHBG levels increase the risk of metabolic syndrome in aging and aged men. They demonstrated that low levels of testosterone are related to lower insulin sensitivity and higher fasting insulin levels (Muller et al 2005). These authors speculate that testosterone might play a protective role in the development of metabolic syndrome, insulin resistance, diabetes mellitus and cardiovascular disease in aging men.
Another recent development is the production of adhesive tablets which are applied twice daily to the buccal mucosa on the gum above the incisor teeth. The tablets gradually release testosterone into the systemic venous circulation and steady state physiological concentrations are achieved in most patients within two days (Ross et al 2004). Some patients do not like the feeling of the tablet in the mouth or find that there is an abnormal taste in the mouth, but local adverse effects are usually mild and transient (Wang, Swerdloff et al 2004).
The finding of hypogonadism in diabetic men is not just a scientific curiosity, it may have practical management implications. Kapoor and colleagues (2006) undertook a placebo-controlled double blind study to determine the effect of testosterone therapy on insulin resistance and glycemic control in hypogonadal men with type 2 diabetes. They found that men treated with testosterone had reductions in glycated hemoglobin insulin resistance, fasting blood sugar, waist circumference, waist/hip ratio and total cholesterol.
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.
×