In recent years, the popularity of testosterone replacement therapy (TRT) has greatly increased. The consensus believed by many is that testosterone levels begin to decline in men about age 40, dropping 0.2 to 2 percent every year after that. This decline in testosterone, however, varies with individuals. Not all men show drastic drops in their testosterone level. What often determines the rate of decline of testosterone is general health and negative health behavior. If your health is bad because of various types of illness, you have a far greater chance of also having low testosterone levels. Indeed, some scientists think that the low testosterone levels shown by many men is more of a reflection of their general health status that any particular perturbation in their hormone system. Bad habits that could also induce low testosterone levels in men include not getting enough sleep. If you get less than 7 hours sleep a night, you have a high likelihood of having low testosterone levels, especially past age 40. Having too much body fat also influences the rate of testosterone production, favoring the conversion of testosterone into estrogen because of increased activity of the aromatase enzyme that resides in body fat and acts to convert testosterone into estrogen. Nutrition also plays a role. If your diet doesn’t contain at least 20% fat, you will likely show lower testosterone levels even if you are young. Excessive stress promotes the release of other hormones that interfere with testosterone release, such as cortisol.
Still, for many men testosterone levels inexorably decline for no clear reasons. One theory about this is that the Leydig cells of the testes, where most of the testosterone in a man’s body is synthesized, are bombarded for years by oxidants that circulate in the blood.This results in a gradual destruction of the Leydig cells that makes them far less responsive to the effects of luteinizing hormone (LH), a pituitary hormone that travels from the brain to the testes, where it dictates the activity of an enzymatic cascade that results in testosterone production. This relationship between oxidation and testosterone production hasn’t been explored much, but will be in an upcoming article in Applied Metabolics. Suffice to say now that animal studies show that if you temper the effects of oxidants through supplying antioxidants to the animals, the usual decline in testosterone starting at middle-age doesn’t happen. Whether this would work for humans has never been explored.
According to medical texts, about 30 to 40 percent of men show low testosterone levels or “Low T” by the time they reach age 40. In my experience, this figure is far higher as I have met or spoken with few men over age 40 who have not shown signs characteristic of declining testosterone levels. These can range from a failure to make any muscular or strength gains in the gym; increased rate of training injuries; depression; lack of sex drive; fatigue; negative changes in sleep patterns; increased body fat, especially in the midsection area;lowered libido or sex drive along with weak or absent erections and other symptoms. Low T is referred to in medicine as hypogonadism and two types exist. Primary hypogonadism, which relates to a failure of the Leydig cells in the testes to produce sufficient testosterone often caused by some type of damage to the testicles from injury or disease. With Secondary hypogonadism the testes still function, but the LH signal from the pituitary gland doesn’t get through. Certain drugs that increase testosterone, besides testosterone itself, require functioning testes to work. These drugs, such as Human Chorionic Gonadatropin(HCG) and Clomid, work by mimicking the effects of LH on the Leydig cells. But they only work if there is still some life left in the Leydig cells. If the remaining Leydig cells don’t respond to these drugs, the only other option is to use some form of testosterone.
Several forms of testosterone exist. The most familiar forms are various types of testosterone injections. Examples of this include testosterone enanthate and testosterone cypionate. These drugs are in a base of oil designed for slow release. They are supposed to last a month, but in reality they peak in two days, then show a slow decline to nearly baseline levels by the two-week mark. Many men who opt to undergo TRT prefer the injection forms because they raise plasma levels of testosterone far higher than other forms. If used weekly in moderate doses of 100 to 200 milligrams, the oil-based testosterone injections will maintain consistently high plasma levels of testosterone. But most physicians frown upon the up and down plasma testosterone levels produced by injections, and also worry about the often highly elevated level of the hormone that peaks after 48 hours. As such, the usual medication to treat TRT in men are various topical versions that avoid the need for injections. These topical versions do maintain steady testosterone levels if used on a regular schedule, keeping the plasma testosterone (T) in the middle ranges, which many physicians think is preferable for long-term health and avoidance of possible side effects. But the patches and testosterone creams are not capable of producing higher plasma testosterone levels and as such are less desirable for men seeking to add muscle mass.