// October 29th, 2010 // 2 Comments » // Hormones

A man’s prostate gland siphons testosterone from his bloodstream. Then an enzyme within the prostate gland converts the trapped testosterone to DHT. It is this DHT made by and retained within the prostate that is one of the factors responsible for prostate gland growth. As far as we know, the prostate gland does not pluck DHT from a man’s bloodstream. Further, when blood DHT levels rise, testosterone levels decline, making less testosterone available for the prostate gland to ensnare. With less testosterone to trap, DHT levels within the prostate gland decline; and prostate growth can be held in check. How do we know this?

Older men given testosterone usually have a slight but significant increase in their prostate specific antigen (PSA) levels. But when similarly aged men are given large doses of DHT, their PSA levels do not change. There are probably two reasons for this. When men receive testosterone supplements, their blood testosterone levels increase, making more testosterone available for the prostate to trap and convert to DHT. But when men receive large doses of DHT, their testosterone levels actually decline. There is not as much bloodstream testosterone for the prostate gland to trap, so less is available for conversion to DHT within the prostate gland.

There is a second and more subtle sequence of events that explains why testosterone, but not DHT, stimulates the prostate to generate more PSA. A female hormone, estradiol, is one of the natural by-products of testosterone metabolism. It turns out that estradiol is yet another stimulus to prostate gland growth. Dihydrotestosterone cannot be further metabolized to estradiol or any other prostate-stimulating estrogen. Thus, giving a man more testosterone will raise blood testosterone, estradiol, and dihydrotestosterone levels. The increases in blood testosterone and blood estradiol provide the prostate with two potent hormonal stimuli to prostate growth. Testosterone does this by being trapped by the prostate gland, and after being transformed to DHT, it can increase the growth of the prostate gland. Estradiol then is free to exert a direct stimulatory impact on other prostate cells.

DHT, on the other hand, does not enter the prostate gland and cannot be transformed into another male hormone or estradiol and therefore deprives the prostate of both testosterone and estradiol, nullifying the growth-promoting impact of these two hormones. As a consequence, neither PSA levels nor prostate size increase during DHT treatment.

The ability of DHT to maintain a male hormone presence while simultaneously lowering estradiol levels is what makes DHT an ideal hormone to treat young boys who develop breast enlargement (gynecomastia). DHT has not yet been approved for this use in this country, but in France, where DHT is approved, teenage boys with gynecomastia have benefited from DHT treatment. Published reports indicate that boys’ breast size returns to normal with DHT treatment.


// October 29th, 2010 // No Comments » // Hormones

Dihydrotestosterone is created when a man’s body decides what to do with all the testosterone he has. By an efficient means of disposal called metabolism, a man’s body is equipped to convert testosterone to other sexually active hormones or innocuous inactive hormones. The testosterone that is manufactured in a man’s testicles is released into his bloodstream and may do a number of things. It can:
1. Act directly on androgen receptors in the brain, muscle, and bone to maintain libido (sex drive), muscle mass, and bone strength;
2. Become a totally different hormone, either a more powerful male hormone called dihydrotestosterone or a female hormone called estradiol (E2);
3. Be transformed into inactive or inert steroid products that have no known function and simply wash out of a man’s system.

Whether testosterone will be converted to a female hormone or a more powerful hormone is not a matter of chance. Different enzymes determine the fate of testosterone. The aromatase enzyme, abundant in fat cells, changes testosterone into the female hormone estradiol (E2). A totally different enzyme called 5-alpha reductase is plentiful only in selected parts of the body, including a man’s prostate and in those hair follicles that grow hair on his head.

Once testosterone (T) enters a man’s prostate gland or his scalp hair follicles, the 5-alpha reductase enzyme goes to work to convert T to DHT, but the rate of transformation of T to DHT may be more aggressive in some men than in others.
Men born without the 5-alpha reductase enzyme cannot convert T to DHT. They seem odd at birth but do grow up to be normal-looking, healthy, well-muscled adult men who have normal T but low DHT levels in their bloodstreams. Men with low DHT levels have a tiny prostate gland as well as a luxuriant head of hair.

They never develop prostate enlargement or go bald!

What would happen if we found a way to lower DHT levels in a normal man? Would his prostate gland shrink? Would he be able to grow more hair on his head? Those were the questions asked by scientists at Merck who went on a diligent search to discover a medication that could allow man to maintain abundant blood testosterone levels while selectively decreasing his DHT. They found finasteride.

Finasteride cross-checks the 5-alpha reductase enzyme and stymies a man’s ability to convert testosterone to dihydrotestosterone. Finasteride pills are now approved for two uses, one to prevent or reverse prostate enlargement in older men and the other to increase scalp hair growth in men who are starting to experience male-pattern baldness. Finasteride pills are packaged in different doses. The 5-mg formulation of finasteride is called Proscar. This medication is often prescribed for middle-aged and older men who are known to have enlarged prostate glands, a condition called benign prostatic hyperplasia (BPH). The 1-mg finasteride dose sold as Propecia is used to treat men who have thinning hair, a condition known as male-pattern baldness.

How well does either finasteride pill work to decrease prostate size or reverse male-pattern baldness?