Men's Health

What is an anti-androgen?

Anti-androgens are drugs that counteract the biological effects of the male hormone testosterone or its active metabolite DHT. They bind to the same androgen receptor as testosterone in specific cells and act as androgen receptor antagonists because they block the biological action of testosterone and DHT working through this receptor. Anti-androgens are either steroidal or non-steroidal and act in a competitive manner for the receptors.

Steroidal anti-androgens

Cyproterone is a steroidal anti-androgen that binds to the androgen receptor competing with testosterone and blocking testosterone binding to its receptor. However, cyproterone does have some biological effects, acting as a weak progestogen and glucocorticoid, which are other hormones involved in production of sex hormones like testosterone. This means that cyproterone does not prevent the production of testosterone completely but reduces the amount of testosterone produced. Cyproterone is used to treat hypersexuality (increased sex drive) and aggression in male sex offenders. It is also used to treat advanced prostate cancer.

Non-steroidal anti-androgens

Bicalutamide is a non-steroidal anti-androgen that binds to the androgen receptor but has no androgen or any other hormonal activity. It does not activate any normal testosterone actions, which means that it does not promote prostate cell growth or testosterone production. Bicalutamide is used to treat advanced prostate cancer, in combination with another medication that induces medical castration by preventing testosterone production by the testes. This blocks the stimulation by testosterone of cancer cell growth and helps slow or prevent progression of the tumour.

What is BHP?

Benign Prostatic Hyperplasia (BPH) is a condition where the prostate gland becomes enlarged due to overgrowth of connective tissue within the prostate gland and also cells that form the lining of the gland. These cells are responsive to testosterone and also convert testosterone into the potent metabolite dihydrotestosterone or DHT, which in turn is thought to stimulate the growth of prostate cells, causing enlargement of the gland. This causes the prostate glad to expand pushing into the urethra, which is the tube taking urine from the bladder and this causes obstruction of urine flow and can cause urinary retention in the bladder. Increased muscle tone of smooth muscle cells in the prostate gland also causes compression of the urethra. Symptoms of BPH include need for frequent or urgent urination, inability to empty the bladder, urinary hesitancy (difficulty starting to urinate) and difficulty passing urine.

Medications for BPH

The medications available for treating BPH are used to reduce the symptoms of BPH by acting directly on cells of the prostate gland to relieve pressure on the urethra, or by blocking an enzyme involved in stimulation of prostate growth. These include:

• Alpha-blockers
• Inhibitors of DHT production

Alpha-blockers

Alpha-blockers, like terazosin and tamsulosin are also known as alpha-adrenergic antagonists. They work by binding to the alpha adrenergic receptor in smooth muscle cells, which blocks the action of naturally occurring adrenergic chemicals like noradrenaline that causes smooth muscle cells to contract and tighten. This allows the muscle in the prostate to relax and relieve pressure on the urethra; this also relaxes the neck of the urethra, which helps urine to flow more easily.

Inhibitors of DHT production

The conversion of testosterone to DHT is carried out in several tissues, including the prostate gland. This conversion is dependent on the action of the enzyme 5α-reductase, which exists in two forms, 5α-reductase I and 5α-reductase II. Drugs that inhibit this enzyme are used to treat BPH and include finasteride, which inhibits type II 5α-reductase and dutasteride inhibits the action of both forms (type I and type II) of the enzyme. 5α-reductase inhibitors reduce the amount of DHT in the prostate, so that growth is no longer stimulated allowing the enlarged prostate to shrink.

Dietary supplements for BPH

A dietary supplement containing an extract of berries from the Saw Palmetto plant, has anti-androgen similar to the 5α-reductase inhibitors and is used to help relieve symptoms of BHP.

What causes ED?

The natural process of sexual stimulation activates a series of biochemical reactions that relaxes blood vessels in the penis and allows blood flow into the corpus cavernosum, which is the spongy erectile tissue of the penis that fills with blood causing an erection. Loss of an erection is due to the activity of an enzyme called phosphodiesterase type 5 (PDE5) that breaks down the chemical responsible for relaxing blood vessels, cyclic guanosine monophosphate (cGMP), which results in contraction of the blood vessels, preventing blood flow. If the natural processes do not function properly due to physical or psychological problems, this can lead to erectile dysfunction or ED.

Medications for ED

The medications available for treating ED are used to increase blood flow into the penis, working by different mechanisms. These are:

• Phosphodiesterase type 5 (PDE5) inhibitors
• Prostaglandins

Phosphodiesterase type 5 (PDE5) inhibitors

Phosphodiesterase type 5 (PDE5) inhibitors block the action of the enzyme PDE5 that prevents blood flow into the penis and this action allows blood to remain in the penis, which maintains an erection. This resolves ED by allowing the natural process of sexual stimulation to activate the mechanism for achieving and maintaining an erection. However, PDE5 inhibitors only work when sexually aroused and do not work otherwise; their effect lasts for around four hours. These medications include sildenafil, tadalafil, vardenafil.

Prostaglandins

Prostaglandin E1, also known as alprostadil, is a naturally occurring chemical that has many functions including relaxation of smooth muscle in various tissues, including the corpus cavernosum and blood vessel walls. Prostaglandin E1 is used to treat ED by direct injection into the penis resulting in widening of the cavernosal arteries in the penis and relaxation of trabecular smooth muscle in the penis. This increases blood flow into the penis causing an erection.

What causes hair loss?

Hair loss in men is an inherited condition called male pattern baldness or androgenic alopecia and this condition accounts for 99% of hair loss in men. This form of hair loss is due to an inherited increased sensitivity to dihydrotestosterone (DHT), which is an active form of testosterone and is converted from testosterone in the hair follicles by the action of the enzyme 5-alpha reductase. Increased conversion of testosterone to DHT is also responsible for hair loss.

DHT in the hair follicles of the scalp is involved in the regulation of hair growth. Normally old hairs fall out to be replaced by new hairs. However, increased action of DHT results in shortening of the anagen or growth phase of the hair cycle, causing the hair follicles to shrink and produce progressively smaller finer hairs, which eventually do not emerge from the follicle. The miniaturised hair follicles then enter a permanent state of catagen or rest phase, instead of resting before a new growth phase. They stop growing and although they are still alive, they cannot produce normal hairs and at this stage the process cannot be reversed.

DHT also stimulates the production of another chemical called transforming growth factor beta (TBG beta), which blocks growth of the skin cells that support hair follicles and eventually cause cell death.

Medications for reducing hair loss

Drugs that inhibit the production of DHT are used in the treatment of male pattern baldness. These include finasteride and dutasteride, which are both inhibitors of the enzyme 5-alpha reductase that converts testosterone to DHT. These drugs reduce the amount of DHT in the hair follicle and slow the progression of balding in men with mild to moderate hair loss, but do not restore hair that has been lost for a long time.