The partial synthesis in the 1930s of abundant, potent testosterone esters permitted the characterization of the hormone's effects, so that Kochakian and Murlin (1936) were able to show that testosterone raised nitrogen retention (a mechanism central to anabolism) in the dog, after which Allan Kenyon's group[183] was able to demonstrate both anabolic and androgenic effects of testosterone propionate in eunuchoidal men, boys, and women. The period of the early 1930s to the 1950s has been called "The Golden Age of Steroid Chemistry",[184] and work during this period progressed quickly. Research in this golden age proved that this newly synthesized compound—testosterone—or rather family of compounds (for many derivatives were developed from 1940 to 1960), was a potent multiplier of muscle, strength, and well-being.[185] 

Testosterone replacement therapy is currently only FDA approved for men who have been diagnosed with hypogonadism, but it’s also prescribed off-label for older men who take it in hopes that it will improve their libido. The use of testosterone therapy is increasingly common in the United States, with more than 2 million men receiving the therapy. Not every man benefits from taking testosterone supplements. Testosterone is available in different forms, including topicals such as gels, creams, and patches; injections; and pellets that are surgically placed directly beneath the skin. (7)
Testosterone fluctuates according to age and life circumstance, often plummeting at the onset of parenthood, and spiking (for some) during moments of triumph. Romantic relationships, too, can impact a person’s testosterone production; though the reasons are still not fully understood, entering a relationship tends to increase women’s testosterone levels, while decreasing men’s. Since males produce significantly more testosterone than females—about 20 times more each day—females can be more sensitive to these fluctuations. High levels of testosterone, particularly in men, have been correlated with a greater likelihood of getting divorced or engaging in extramarital affairs, though a causal link has not been established.
Longitudinal studies in male aging studies have shown that serum testosterone levels decline with age (Harman et al 2001; Feldman et al 2002). Total testosterone levels fall at an average of 1.6% per year whilst free and bioavailable levels fall by 2%–3% per year. The reduction in free and bioavailable testosterone levels is larger because aging is also associated with increases in SHBG levels (Feldman et al 2002). Cross-sectional data supports these trends but has usually shown smaller reductions in testosterone levels with aging (Feldman et al 2002). This is likely to reflect strict entry criteria to cross-sectional studies so that young healthy men are compared to older healthy men. During the course of longitudinal studies some men may develop pathologies which accentuate decreases in testosterone levels.
Erectile dysfunction is a common finding in the aging male. A prevalence of over 70% was found in men older than 70 in a recent cross-sectional study (Ponholzer et al 2005). Treatment with phosphodiesterase-5 (PDE-5) inhibitors is proven to be effective for the majority of men but some do not respond (Shabsigh and Anastasiadis 2003). The condition is multi-factorial, with contributions from emotional, vascular, neurological and pharmacological factors. The concept of erectile dysfunction as a vascular disease is particularly interesting in view of the evidence presented above, linking testosterone to atherosclerosis and describing its action as a vasodilator.
Findings that improvements in serum glucose, serum insulin, insulin resistance or glycemic control, in men treated with testosterone are accompanied by reduced measures of central obesity, are in line with other studies showing a specific effect of testosterone in reducing central or visceral obesity (Rebuffe-Scrive et al 1991; Marin, Holmang et al 1992). Furthermore, studies that have shown neutral effects of testosterone on glucose metabolism have not measured (Corrales et al 2004), or shown neutral effects (Lee et al 2005) (Tripathy et al 1998; Bhasin et al 2005) on central obesity. Given the known association of visceral obesity with insulin resistance, it is possible that testosterone treatment of hypogonadal men acts to improve insulin resistance and diabetes through an effect in reducing central obesity. This effect can be explained by the action of testosterone in inhibiting lipoprotein lipase and thereby reducing triglyceride uptake into adipocytes (Sorva et al 1988), an action which seems to occur preferentially in visceral fat (Marin et al 1995; Marin et al 1996). Visceral fat is thought to be more responsive to hormonal changes due to a greater concentration of androgen receptors and increased vascularity compared with subcutaneous fat (Bjorntorp 1996). Further explanation of the links between hypogonadism and obesity is offered by the hypogonadal-obesity-adipocytokine cycle hypothesis (see Figure 1). In this model, increases in body fat lead to increases in aromatase levels, in addition to insulin resistance, adverse lipid profiles and increased leptin levels. Increased action of aromatase in metabolizing testosterone to estrogen, reduces testosterone levels which induces further accumulation of visceral fat. Higher leptin levels and possibly other factors, act at the pituitary to suppress gonadotrophin release and exacerbate hypogonadism (Cohen 1999; Kapoor et al 2005). Leptin has also been shown to reduce testosterone secretion from rodent testes in vitro (Tena-Sempere et al 1999). A full review of the relationship between testosterone, insulin resistance and diabetes can be found elsewhere (Kapoor et al 2005; Jones 2007).
Intramuscular testosterone injections were first used around fifty years ago. Commercially available preparations contain testosterone esters in an oily vehicle. Esterification is designed to retard the release of testosterone from the depot site into the blood because the half life of unmodified testosterone would be very short. For many years intramuscular preparations were the most commonly used testosterone therapy and this is still the case in some centers. Pain can occur at injection sites, but the injections are generally well tolerated and free of major side effects. Until recently, the available intramuscular injections were designed for use at a frequency of between weekly and once every four weeks. These preparations are the cheapest mode of testosterone treatment available, but often cause supraphysiological testosterone levels in the days immediately following injection and/or low trough levels prior to the next injection during which time the symptoms of hypogonadism may return (Nieschlag et al 1976). More recently, a commercial preparation of testosterone undecanoate for intramuscular injection has become available. This has a much longer half life and produces testosterone levels in the physiological range throughout each treatment cycle (Schubert et al 2004). The usual dose frequency is once every three months. This is much more convenient for patients but does not allow prompt cessation of treatment if a contraindication to testosterone develops. The most common example of this would be prostate cancer and it has therefore been suggested that shorter acting testosterone preparations should preferably used for treating older patients (Nieschlag et al 2005). Similar considerations apply to the use of subcutaneous implants which take the form of cylindrical pellets injected under the skin of the abdominal wall and steadily release testosterone to provide physiological testosterone levels for up to six months. Problems also include pellet extrusion and infection (Handelsman et al 1997).
Studies also show a consistent negative correlation of testosterone with blood pressure (Barrett-Connor and Khaw 1988; Khaw and Barrett-Connor 1988; Svartberg, von Muhlen, Schirmer et al 2004). Data specific to the ageing male population suggests that this relationship is particularly powerful for systolic hypertension (Fogari et al 2005). Interventional trials have not found a significant effect of testosterone replacement on blood pressure (Kapoor et al 2006).
"Some say it's just a part of aging, but that's a misconception," says Jason Hedges, MD, PhD, a urologist at Oregon Health and Science University in Portland. A gradual decline in testosterone can't explain a near-total lack of interest in sex, for example. And for Hedges' patients who are in their 20s, 30s, and early 40s and having erectile problems, other health problems may be a bigger issue than aging.
Testosterone is necessary for normal sperm development. It activates genes in Sertoli cells, which promote differentiation of spermatogonia. It regulates acute HPA (hypothalamic–pituitary–adrenal axis) response under dominance challenge.[22] Androgen including testosterone enhances muscle growth. Testosterone also regulates the population of thromboxane A2 receptors on megakaryocytes and platelets and hence platelet aggregation in humans.[23][24]

The partial synthesis in the 1930s of abundant, potent testosterone esters permitted the characterization of the hormone's effects, so that Kochakian and Murlin (1936) were able to show that testosterone raised nitrogen retention (a mechanism central to anabolism) in the dog, after which Allan Kenyon's group[183] was able to demonstrate both anabolic and androgenic effects of testosterone propionate in eunuchoidal men, boys, and women. The period of the early 1930s to the 1950s has been called "The Golden Age of Steroid Chemistry",[184] and work during this period progressed quickly. Research in this golden age proved that this newly synthesized compound—testosterone—or rather family of compounds (for many derivatives were developed from 1940 to 1960), was a potent multiplier of muscle, strength, and well-being.[185]
"Bring back the younger inner you," says the Low T Center. According to its website, its president, Mr. (notably not "Dr.") Mike Sisk, "created these centers out of a need." They promise their testosterone injections "do not just help boost a low sex drive but can also boost energy, decrease body fat, irritability, and depression." They go so far as to claim that "research finds testosterone replacement can solve long-term health issues like Alzheimer's and heart disease."

What you need to know about STDs Sexually transmitted diseases (STDs) are infections that are passed on from one person to another through sexual contact. There are many STDs, including chlamydia, genital warts, syphilis, and trich. This article looks at some of the most common STDs, the symptoms, and how to avoid getting or passing an STD one on. Read now
When stimulated by the nerves, the spongy tissue arranges itself in such a way that more blood can be stored in the penis. The veins running through the outer sheath of the penis then compress which stops the blood from leaving the penis. As the blood is stopped from flowing out, the penis fills with blood and stretches within the outer casing, giving an erection.
In rare cases, the drug Viagra ® can cause blue-green shading to vision that lasts for a short time. In rare cases, the drug Cialis® can cause or increase back pain or aching muscles in the back. In most cases, the side effects are linked to PDE5 inhibitor effects on other tissues in the body, meaning they are working to increase blood flow to your penis and at the same time impacting other vascular tissues in your body. These are not ‘allergic reactions'.
The availability of phosphodiesterase-5 (PDE5) inhibitors—sildenafil, vardenafil, tadalafil, and avanafil—has fundamentally altered the medical management of ED. In addition, direct-to-consumer marketing of these agents over the last 15 years has increased the general public’s awareness of ED as a medical condition with underlying causes and effective treatments.

Best of all? It's easy. "Low T Center is set up so men can walk in, take a simple blood test, and know within 30 minutes whether or not they are a candidate for testosterone replacement therapy, or TRT. Men who qualify get their first injection on the spot, and will continue to come in three times per month to receive a quick testosterone injection."

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