What Is Dihydrotestosterone (DHT)?

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Dihydrotestosterone (DHT) is a metabolite of testosterone. It has similar but much stronger effects. DHT is estimated to be three to six times more powerful than testosterone. Both hormones are classified as androgens. DHT is primarily created in the organs where it is used, such as the prostate. The enzyme 5-alpha reductase is primarily responsible for converting testosterone to DHT.

Interestingly, testosterone and DHT both bind to the same receptors. However, DHT does so more efficiently. In addition, the responses to DHT and testosterone binding are different. Most DHT in the body is bound to proteins, such as albumin and sex hormone binding globulin, in the blood. This is also true for testosterone. With DHT, less than 1 percent of the hormone in the blood is circulating freely. This is slightly lower than the amount of free versus bound testosterone.

Albumin can bind a large amount of testosterone or other sex hormones but binds those hormones quite weakly. Sex hormone binding globulin, in contrast, binds less hormone but does so more strongly.

Function

Dihydrotestosterone has a number of effects on the human body. In addition to serving as a stronger form of testosterone, it is also a precursor of other steroid hormones.

As a broad overview, an overproduction of DHT is known to cause a number of undesirable health effects in men including enlargement of the prostate and male pattern baldness.

It can also cause hirsutism and female pattern baldness. In contrast, lack of DHT production can lead to differences in sexual differentiation such as androgen insensitivity syndrome.

Significance

The significance of dihydrotestosterone differs in different organs. High levels of DHT are problematic in some areas of the body, while it is necessary in others.

Prostate Disease

DHT stimulates the growth of two types of cells within the prostate: epithelial cells and stromal cells. Interestingly, DHT works in combination with estrogen to lead towards prostate enlargement. The estrogens that are more common in older men increase the number of hormone receptors in the prostate. Then, with more hormone receptors, DHT more efficiently leads to prostate growth.

DHT is commonly associated with Benign Prostatic Hyperplasia (BPH). BPH can cause symptoms such as difficulty urinating, needing to urinate more frequently, and other urinary issues. DHT induced prostate growth can sometimes be treated with drugs that reduce DHT concentrations such as finasteride. Finasteride is a 5-alpha-reductase inhibitor.

Male Pattern Baldness

Androgens are important for the hair-growth patterns associated with puberty. However, not all hair follicles react to androgens in the same way. In particular, an excess of DHT has been associated with both beard growth and male pattern baldness. This is why anti-DHT medications can be used to improve hair growth on the scalp in men who are experiencing male pattern baldness.

Interestingly, pubic hair and underarm hair growth seem to be stimulated by testosterone rather than dihydrotestosterone.

Hirsutism

Women who experience extra facial and body hair growth may do so because of an overproduction of DHT. Although it may seem confusing, in such women, blocking DHT can reduce unwanted hair growth. This is often done with the same drugs used to increase hair growth among balding men.

Why do the same drugs have the opposite effects? It's because hair follicles in each area of the body have evolved to respond to differently to different types of hormones. In women, when hair loss on the scalp is related to hormonal issues (androgenic alopecia), it may also be treated by the same types of drugs.

DHT and Sexual Development

In addition to its role in general health and disease, DHT has a number of effects on sexual development and sexual function.

In particular, DHT plays an important role in the development of male external genitalia.

XY-infants who do not produce DHT, due to 5-alpha reductase deficiency, are born with feminized genitalia or ambiguous genitalia.

Certain forms of DHT deficiency, affecting only one of the two 5-alpha reductase enzymes, may reverse with puberty, although these forms are rare outside of specific populations. XX-individuals with a 5-alpha-reductase deficiency may experience a delayed start of menstruation and decreased body hair growth.

At puberty, DHT is critical for penile growth. It works in combination with testosterone to increase the size of the male external genitalia. This does not mean that taking testosterone or DHT will increase your penis size. Adult men who have completed puberty no longer have androgen receptors in their penile tissue.

Sexual Function

The role of DHT in male sexual function is still somewhat controversial. Much of the data is indirect, coming from studies of 5-alpha reductase inhibitors rather than studies of DHT levels directly That said, a number of studies have shown an increase in erectile dysfunction in men taking 5-alpha reductase inhibitors to decrease their DHT levels. These medications have also been shown to decrease libido and sex drive. As such, it is generally held that DHT plays an important role in male sexual desire and function.

Although drugs that reduce DHT also cause problems for male sexual function, it is not necessarily true that DHT treatment would improve sexual function. Higher levels may not always be better. DHT levels interact with the levels of other steroid levels in the blood, and increasing DHT can decrease other hormones, such as estrogen. This could potentially have a negative effect on male sexual function.

Fertility

The effects of DHT on male fertility are not yet clear. The enzymes that produce DHT are present in the prostate, the penis, and the scrotum. However, they are not present in the testes. This suggests that spermatogenesis does not require DHT.

However, some data suggests that 5-alpha reductase inhibitors can affect sperm production, at least temporarily. Use of these drugs has been associated with a decreased sperm count and lowered semen volume in some studies It has also been associated with reduced sperm motility.

Fortunately, these effects seem to be reversible when treatment is discontinued. Furthermore, other studies have not seen changes in sperm parameters with low-dose finasteride, so further research is still needed.

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