The Complete Book of Men's Health - Part 1: Sexual Health

PUBERTY

Puberty is the stage between childhood and adulthood when secondary sexual characteristics develop, the sexual organs mature, and reproduction becomes possible. Emotional changes also occur and these, plus the physical changes of puberty, are referred to as adolescence.

In boys puberty usually starts between the ages of 10 and 14 years (although many hormonal changes can occur undetected before this time) and is complete by the age 15 to 17 years. It generally starts a year earlier in girls (age 9 to 13) when a good sign that puberty is in full swing is the appearance of the first menstrual bleed. In males, a similar stage of maturity is indicated by the occurrence of the first ejaculation. This often occurs at night, as a so-called 'wet dream'. This does not signify fertility, and is merely an indication that the testes have awakened and, together with the seminal vesicles and prostate gland, are starting their secretory function.

What triggers puberty is not fully understood. It may be due to the withdrawal of inhibitory nerve connections which damp down a part of the brain called the hypothalamus. Once this inhibition is removed, the hypothalamus releases pulses of a trigger substance called Leutinising Hormone-Releasing Hor-mone (LHRH). These LHRH pulses pass down nerve endings to stimulate the pituitary gland just beneath the hypothalamus, at the base of the brain.

The stimulated pituitary starts to secrete two other hormones which are essential for reproduction. These two hormones are Follicle Stimulating Hormone (FSH) and Leutinising Hormone (LH). FSH and LH enter the bloodstream and travel around the body to switch on the ovaries in females, or the testicles in males. FSH triggers the production and development of sperm, and LH triggers the production of the male hormone testosterone.

TESTOSTERONE AND ITS IMPORTANCE

Testosterone is the most important androgen, or male sex hormone. In males, 95 per cent is secreted by the testicles, with a small amount (5 per cent) also coming from the adrenal glands. A mature male secretes between 4 and 10 mg of testosterone per day. In females, small amounts of testosterone are also secreted by the adrenal glands and ovaries.

In each testis, the spaces between the convoluted seminiferous tubules (see Chapter 3) are filled with nests of cells called the interstitial cells of Leydig. These contain fatty granules rich in cholesterol which are converted into testosterone through a series of chemical reactions. Testosterone is released into the bloodstream to stimulate the growth of bone and muscle, enlargement of the genitals and testicles, and sexual development. It is responsible for the male secondary sex characteristics that occur at puberty, and for sperm production.

The Effects of Testosterone Hormone

Testosterone hormone is responsible for:

• maintenance of male sex drive

• growth of the larynx and deepening of the voice

• growth of the penis, testes and scrotum

• development of rugged folds (rugae) in scrotal skin

• growth of the seminal vesicles and secretion of fluids rich in the sugar fructose

• growth of the prostate gland

• secretion of prostate fluids

• stimulation of sperm production

• maintenance of erectile/ejaculatory function

• fusion of bone ends (epiphyses)

• maintenance of muscle bulk.

Testosterone is broken down in the prostate gland and in hair follicles to form another hormone called dihydro-testosterone. This is twice as potent as testosterone and is thought to be responsible for:

• the growth of facial, armpit and limb hair

• maintenance of male-pattern pubic hair

• male pattern baldness

• acne

• benign enlargement of the prostate gland

The conversion of testosterone to dihydro-testosterone is controlled by an enzyme, 5-alpha-reductase. Males who lack this enzyme are genetically male, with normal functioning testicles, but are mistaken for girls until puberty. This is because their external genitals are sufficiently small and rudimentary to resemble those of the female. Once puberty starts, the presumed clitoris rapidly enlarges to become a penis and the 'labia' unfold to form a scrotum into which the testicles suddenly drop.

This defect is relatively common in a part of the Dominican Republic, where it is accepted as normal that a few of the little girls playing in the streets will grow up and turn into men. Those affected are known as 'guevedoces' meaning 'penis at twelves'.

These males seem to swop their psychosexual identity with no difficulty and, despite being reared as females, start functioning behaviourally as males. Interestingly, they do not develop acne, do not become bald and do not develop benign prostatic enlargement in later life.

These findings have helped researchers understand that it is dihydro-testosterone, and not testosterone, that may be responsible for male pattern baldness (see hair loss) and benign prostatic enlargement.

PUBERTAL GROWTH SPURT

In boys, the peak growth spurt occurs between the ages of 12 and 17. This is controlled by both testosterone and growth hormone, with virtually every muscle and bone in the body affected. Differential growth in males means the shoulder girdle broadens more than the hips.

Changes also occur in body composition, so that lean body mass (muscle) increases while body fat percentage decreases so pubertal boys lose their chubbiness. The five stages of male genital development are indicated below. Ages given are the average for the onset of each stage:

Stage 1: pre-adolescence ­ penis, testes and scrotum of similar size and proportion as in early childhood

Stage 2: scrotum and testes enlarge; left testicle usually hangs lower than the right; the scrotum becomes baggier, slightly furrowed (rugose) and reddened; spermatogenesis begins (age 10­13)

Stage 3: testes and scrotum grow larger; penis first starts to lengthen, then becomes broader; sparse pubic hair develops; facial hair appears on upper lip and cheeks; body hair starts to appear on limbs and trunk (age 11­14)

Stage 4: further enlargement of testes and scrotum; scrotum darkens and becomes more furrowed; penis continues enlarging and glans starts to develop; pubic and body hair become more profuse, with hair growing around the base of the penis; major growth spurt occurs (age 13­17)

Stage 5: adult stage, with genitals fully matured; pubic hair extends up the abdominal midline in male pattern; facial hair extends to lower lip and chin (age 17­18)

Breaking Voice

Testosterone causes the male voice box (larynx) to enlarge and the vocal cords to become longer and thicker. This causes the pitch of the voice to drop; this deepening of the voice is often referred to as the voice 'breaking'. This tends to occur around the age of 14, but the majority of boys do not notice it is happening as the changes are gradual. Some boys notice a tight feeling in their throat which passes after a few weeks, and may be accompanied by a croaky voice. This is nothing to worry about.

MALE SEXUAL BEHAVIOUR

In human males, sexual behaviour is dependent on testosterone hormone. This produces increased sexual interest and sex drive and intensifies innate patterns of sexual behaviour. Giving testosterone to heterosexuals increases their interest in the opposite sex, and the administration of testosterone to homosexual males intensifies their homosexual drive ­ it does not convert it into a heterosexual one.

In a study of over 4,000 American men it was found that husbands with high testosterone levels were 43 per cent more likely to get divorced and 38 per cent more likely to have extramarital affairs than men with lower levels. They were also 50 per cent less likely to get married in the first place.

Men with the lowest testosterone levels were more likely to get married and to stay married successfully. This may be because low testosterone levels make men more docile, less aggressive, better humoured and more home loving.

Interestingly, testosterone levels seem to affect the career a man will follow. Those with highest testosterone levels are likely to become athletes, actors and entertainers ­ professions that are associated with competitive, aggressive or extrovert behaviour.

Some chemicals have an anti-testosterone action and are called anti-androgens. The administration of cyproterone acetate or medroxyprogesterone acetate can decrease the male sex drive and interfere with the ability to produce an erection. These drugs are sometimes used to treat sex offenders.

Castration (removal of the testes) is eventually followed by a reduction in sexual activity, but this may not be for several years. In many cases, sexual activity does not peter out altogether. This may be due to an increased output of testosterone from the adrenal glands, which usually only provide 5 per cent of circulating testosterone levels.

In males who do lose their sex drive and ability to have erections, treatment with testosterone replacement effectively reverses these changes and restores sexual activity to its former level.

What Is A Normal Sex Drive?

According to various surveys, 40 per cent of British couples make love more than three times per week, 35 per cent make love once or twice a week and 15 per cent make love two to three times per month. Nine per cent of couples make love less than this or not at all.

The National Survey of Sexual Attitudes and Lifestyles in the UK (published in 1994) found that men aged 25­34 years of age made love around five times per month. As age rose to 55­59 years, levels of activity fell to twice per month.

According to The Esquire Survey (1992) of 800 men, 2 per cent of males have sex once a day or more and 11 per cent have sex four to six times per week. The most common frequency seems to be two to three times per week. Only 5 per cent of non-virgin males were not actively indulging in sexual relationships.

The duration of a relationship is also significant. Other surveys have found that over 50 per cent of couples together for under three years make love more than three times per week. After four or more years together, only 25 per cent maintain this frequency.

Aphrodisiacs

A number of aphrodisiacs have proved popular over the ages. Most derive from obviously phallic articles. The association of powdered rhinoceros horn and bananas with hardness and virility is easy to see, but feasting on the still warm brains of recently decapitated criminals seems eccentric ­ until you realize that erection is a common side-effect of sudden spinal trauma. This is known rather cruelly as 'Custer's Last Stand'. Safer reputed aphrodisiacs include oysters, champagne, ginseng, Eleuther-ococcus (Siberian ginseng) and, surprisingly, raspberries.

Pheromones

Pheromones are volatile chemicals that are secreted in very small amounts in our skin oils. They are mostly undetectable at a conscious level but have powerful effects on mood. Pheromones are thought to be the key to human sexual attraction, and recently the first one to be isolated (from skin fragments within a discarded orthopaedic plaster cast) was studied for its effects. Liquid concentrates of this human pheromone were tested on 40 volunteers, and feelings described as 'a contented high' put pheromone recipients into a friendly, responsive mood. Extracts may be added to aftershave and skin perfumes in the near future, perhaps with devastating effects.