SCIENCE: WHY EUNUCHS DON'T WEAR TOUPEES

SCIENCE has been notoriously puzzled by why men lose their locks - a situation keenly exploited by all manner of shysters who have raised hopes and their bank balances with a multitude of potions "guaranteed" to make hair grow. But in recent years, strands of evidence about how hair works - gleaned from biochemistry, genetics and modern lifestyles - have started to come together, and while they may not yet be enough to cover the bald spot, they hold more hope than a toupee.

For a start, it's now known it's not only men who have the potential to lose their crowning glory. "Male pattern baldness" - which affects about 30 per cent of men in their 30s and 40 per cent in their 40s - is in fact "pattern baldness", and linked to two key factors: genetic inheritance and a derivative of the male hormone testosterone, called dihydrotestosterone or DHT. The same mechanism is at work in women, but the characteristic pattern of thinning hair at the temples, crown and top of the head, doesn't kick in until after menopause when women lose the protection of their female hormones.

The genetic disposition to gradually bald can come from either parent and may depend on one or several genes. Last month, US researchers pinpointed the human equivalent of a mouse gene dubbed "hairloss" by investigating 11 members of a family who have lost all their hair, a condition known as alopecia universalis. But this gene - though possibly a master-switch in the hair-making pathway and a breakthrough in general terms - is unlikely to be much consolation for the average baldy because it affects all follicles, not just those on top.

The genetic influence in pattern baldness, on the other hand, causes hair follicles on the front, top and crown of the head to end up different from those on the sides. What makes them different is that they carry receptors susceptible to DHT, the chemical made by the body from testosterone from around puberty.

DHT alters the growing cycle of hair. Silken tresses normally result from a long growing phase - two years or more - followed by a short resting phase. But DHT gradually reverses this cycle until eventually the resting period is so long that there's no new hair coming through to replace the 100 to 150 hairs we lose daily as part of natural shedding.

The same genetic pattern occurs in women, but because they have smaller amounts of testosterone, which for much of their lives is buffered by female hormones, pattern balding only starts to occur after the menopause. And, since DHT works by persistent attrition over time, this late start means women generally only experience thinning hair as they grow older and rarely get bald spots. Taking HRT with its boost of female hormones can postpone it even further.

Only scalp hair can be affected by DHT; body hair is controlled by testosterone itself. And the hair follicles on the sides and back of the head never acquire the DHT receptor, hence the success of surgery which transplants hair follicles from these areas to bare spots on the crown.

Of course, DHT's sole purpose is not to make men miserable by causing their hair to fall out. In youth, it prompts the prostate gland to grow and develop the structures that produce semen, while after age 50, it starts enlarging the gland again, though for little apparent reason.

Why exactly we have DHT receptors in the scalp is still one of life's little mysteries, though evolutionists suggest there must be some benefit to going bald to cause the genes to be retained.

Yet another puzzle is what makes DHT begin acting at different ages. Why for some men does a widow's peak start appearing at puberty while others don't have to start combing their hair strategically until they are 30, 40 or 50. One theory used to be that balding men were testosterone- charged - hence the sexy label - but studies have spiked that consolation, finding that all men have roughly the same amount of circulating testosterone and DHT, regardless of the state of their hair.

Given such little real knowledge, it's not surprising that finding a cure for pattern baldness has proved elusive. Until recently, only one treatment for hair loss offered any evidence of success and that seemed to have nothing to do with DHT.

Minoxidil (or "Regaine") was discovered when some men testing an oral- form of the drug as a treatment for high blood pressure reported hair growth. Now rubbed on as a lotion, it can slow down hair loss, but only 8 per cent of men get real hair growth, while a third get baby fluff, as do a similar proportion who rub their recalcitrant scalps with a placebo lotion for four months.

Studies have shown minoxidil works by opening "potassium channels" - doors that lets potassium out - in cells, says Dr Terence Kealey, a medical biochemist at Cambridge who is searching for a better rub-on agent. As the potassium leaves, calcium - a mineral which activates cell proliferation, in this case hair cells - enters. But how this fits together with DHT's effect is a "big black box", says Kealey. "What we know is that at one end of the chemical trail minoxidil potentiates the message to grow and at the other DHT knocks it back."

Last Christmas, a second treatment was licensed by the US Food and Drug Administration - a once-daily pill hailed as a chance for leonine locks for a lifetime. Called Propecia, it contains a low dose of finasteride, a drug originally developed to counter prostate enlargement by blocking the conversion of testosterone into DHT.

In US trials, finasteride stopped hair loss in 80 per cent of men, and maintained this for two years. Two thirds of men gained hair over the trial period, though British clinicians say in practice fewer than a third regain "cosmetically significant" hair. Finasteride is not yet licensed for hair loss here, though it is licensed as a treatment for prostate enlargement and doctors can prescribe it privately. But it's no magic bullet: it has to be taken constantly, its long term effects are unknown, and it can influence sex drive and erections - albeit in less than 2 per cent of men according to US trials.

If you don't fancy drugs, surgery or resignation, Dr Nilofer Farjo, Harley Street surgeon and expert in balding treatments, suggests the only other way to prevent pattern balding is castration. "A bit drastic but eunuchs don't go bald," she notes.

Andy Bryant, director of Natural Hair Products, begs to disagree. Having saved his own head of hair with no loss of body parts, he now advises up to 1,500 people a year on lifestyle changes which he says can slow hair loss and give measurable regrowth. His prescription is simple: reduce stress, reduce or cut out tea, coffee, alcohol and high sugar foods. All, he argues, increase stress hormones such as adrenalin and prolactin which increase levels of testosterone and consequently DHT.

"If you stabilise the over-reaction of the adrenal glands, the rate of hair loss slows quickly," says Bryant, who is convinced that whatever the genetic background, levels of circulating DHT are the key. In countries where tea, coffee, alcohol and sugar consumption is low, he notes, pattern baldness is less prevalent, as is prostate cancer. When Japanese men move to the US, their rate of prostate cancer increases three to five times, and Japanese researchers, who believe consumption of more animal fat is giving Japanese men increasingly greasy scalps have also reported a link between excessive oil in the scalp and hair loss.

As well as dietary and lifestyle changes, many of Bryant's clients take saw palmetto, a berry thought to have mild anti-DHT effects, and some regularly hang upside-down to increase blood flow to the scalp - though medical doctors insist pattern baldness has nothing to do with poor circulation, which would affect the whole scalp.

Bryant's method has not been placebo-trialed - "losing hair is so traumatic, it doesn't seem fair," he says. But clinical investigation of 70 clients showed hair loss stopped in 70 per cent and almost 50 per cent had achieved measurable regrowth after three to six months. After three to four years, some men have three quarters of their crowning glory back.

These results are similar to finasteride, says Bryant, even down to the pattern of regrowth which sees hair returning to the back and top of the head, while the temples remain stubbornly slick, but with no risk of side effects.

Medical experts tend to dismiss lifestyle approaches, arguing that changing diet or reducing stress won't change hair follicles genetically programmed to fail. But the strains of modern life could explain a phenomenon clearly identified by both medics and alternative proponents. And that is that men are balding earlier.

"We are seeing men who are 20 who have exactly the same level of hair loss as their dad did at 40," says Dr Farjo. !

THE BALD FACTS

l The scalp has 100,000 to 350,000 hair follicles which produce hair in cycles.

l Hair grows an average of 1.25cm a month, growing fastest in summer and slowest in winter, speeding up under heat and friction and slowing when exposed to cold.

l Not washing your hair in the mistaken belief that it will prevent it falling out will make it look darker and thicker, because of the dirt and grime coating each hair and those that should have fallen out stay stuck in the head, but it's not going to do much for your social life.

l Cleopatra gave Caesar a greasy mix of deer's marrow, horses' teeth and bear oil to counter his bald spot

l Other "tried and true" remedies include rubbing with marmite, curry, chicken manure or Baby Bio - on the basis that they increase circulation. Hanging upside down works on the same principle, but fails to explain why only the hair on the top of the head is lacking blood.

l Being licked by a cow may work - the chemicals in cow saliva may stimulate growth factors in the scalp.