Part of the pleasure in sex for women is the experience within her vagina, whose elasticity and thickness are maintained by oestrogen. After the menopause, a thinning drying vagina can be a bar to sexual enjoyment. Orgasm, however, is maintained by another hormone altogether.
When a women has an orgasm, her womb contracts. Intrauterine pressures increase, as does vaginal pressure. When orgasm is over, the intrauterine pressure drops very rapidly, creating a pressure gradient. The cervix dips and then, thanks to that pressure gradient, literally hoovers sperm into the womb. Orgasm isn’t strictly necessary to conception, but it is designed to make the most of your chances. Oxytocin is the hormone at work here. It is thought of as the hormone of birth. Indeed, the word oxytocin comes from the Greek for ‘quick birth’ and under its influence the womb – which is made of smooth muscle – contracts rhythmically and powerfully to expel the baby.
Almost all of a woman’s genital apparatus is made of smooth muscle (which is under involuntary control, unlike the striped muscles of, say, your biceps). Oxytocin is responsible for the dilation of your pupils as you orgasm, the gaping of the cervix into a round ‘O’ (which, incidentally, is mirrored in the shape of your mouth during orgasm) and the rhythmic contractions of orgasm. The greater the amount of oxytocin, the more intense the orgasm. And the better the orgasm, the more oxytocin is knocking about to ensure that you bond with the man that thought he, rather than your hormones, was responsible for your pleasure. So is this surge of oxytocin all about your pleasure? No. The point of the contractions is to ensure egg and sperm transport. The contraction is so exquisitely directed that the human female is capable, if necessary, of organizing egg and sperm movement in opposite directions at the same time.
In the mid-1990s zoologist and evolutionary biologist Dr Robin Baker claimed that women were effectively able to sort sperm in utero, actively choosing that ejaculate which was most favorable from amongst multiple partners. Lest that in itself sounds improbable, a Britsh sex survey of the 1980s revealed that over 70 per cent of women had during their lifetime slept with two men within the space of five days; nearly 70 per cent had done so within a day of each other and 1 per cent claimed to have done so within thirty minutes.
Despite taking these surveys with a pinch of salt – how many of us have filled in the ‘five times a night’ box during a boring lunch hour spent with our mates, only for it to be taken at face value by an unquestioning academic – there is evidence throughout the animal world of active sperm-sorting. Hamsters, for instance, are very selective about sperm, allowing only a few of the millions deposited through. Nevertheless fertilization rates are close to 100 per cent. Female mice are able to recognize which sperm are more compatible – in terms of compatible MHC ( Major Histocompatibility Complex ) – and sperm that are deemed a bad match are left behind. Polyandry – multiple mating -is the norm in many animals and a capacity for active vaginal sorting allows the fittest sperm to be selected for fast-track access to the ovum.
Robin Baker outlines his theories on the subject in his book Sperm Wars. His ideas are intriguing, although it has to be said, in humans at least, distinctly light on proof. But the sorting mechanisms he proposes depend on muscle movement initiated by oxytocin. However, recent work from the University of Memphis, published in the journal Nature, has strengthened the concept of sperm competition, revealing that there is an increase in the amount of sperm in the ejaculate of meadow voles able to smell rival suitors in the air, when pursuing their volette.
It is often assumed that male sexual performance is dictated by testosterone and that if men have erection problems, it is all down to a lack of testosterone. As far as sex is concerned, testosterone is the hormone of sex drive and desire, rather than the hormone which controls function of the penis. It is rather unusual for erectile dysfunction to be caused by a hormone problem. Difficulties with erections are more likely to be caused by faults in the exquisitely designed hydraulic system on which a rampant penis depends. The mechanics of it are dictated by blood flow and it is alterations in blood flow caused by narrowed arteries, diabetes, prescription drugs, drinking or smoking that are the principal cause of dysfunction. In fact, there is nothing more frustrating to a man than having all his hormones in full flood, goading him on, only to discover that he has a non-playing member on the team. Poor levels of testosterone in men are in fact not a normal cause of impotence.
Lack of testosterone may, in fact, be more of a problem in women in terms of sexual dysfunction. The tissue of women’s genitals are androgen-dependent, including the pubic hair and nipples as well as the labia and clitoris. You will recall that the adrenals churn out androgens – male hormones – in both men and women.
The ovaries also produce testosterone: some is manufactured start to finish, as it were, but about half of it is made from semi-assembled raw material, supplied in the form of the androgen DHEA, produced by the adrenals. In fact, the most abundant sex hormone in women’s circulation is not oestrogen but the androgen DHEA, or, to be strictly accurate, its sulphated form DHEAS. One of the functions of DHEAS is as a semi-finished construction material, handy for conversion into testosterone in sites like hair follicles, but it is also important as a construction material for oestrogen production.
As women age, levels of testosterone fall, by roughly half from twenty to forty years of age. This is not simply because of decreasing amounts of testosterone being produced, but because of an increase in the amount of those steroid chaperones, SHBGs, which lock up more of what is being produced and make even less ‘free’ testosterone available. There has been an attempt of late to medicalize sex problems in women. The manufacturers of testosterone implants would have us believe that 40 per cent of women have sexual dysfunction requiring medical treatment. There are certainly physiological problems that affect women’s desire and arousal, just as there are in men, such as decreased blood flow through poor general health and prescription drugs (especially the pill, Valium and some of the SSRIs (Selective Serotonin Reuptake Inhibitors) used for depression). Such problems are no doubt greatly under-reported and when they are, are not dealt with all that sympathetically.
However, whether the testosterone fall with age is responsible for declining sexual activity in women is a moot point. Researchers at the Jean Hailes Foundation in Australia, who tracked changing hormone levels with age in a large group of women as part of the Sue Ismiel International Study into Women’s Health and Hormones, found that low testosterone levels bore no significant relationship to low libido in women from age eighteen right up to seventy-five. But they did find that a low DHEA level made it three times more likely that there would be poor sexual function remember, DHEA is made into both testosterone and oestrogen.
Sex has never just been about physiology. There is a strong psychological factor too and the belief that a pill, testosterone, DHEA or whatever could magically conjure desire and arousal when all you have at home is a boring, overweight smelly bloke whose idea of fore-play is to say ‘turn over, it’s your lucky night’ is unlikely to say the least. Having said all of that, testosterone implants, pills and supplements of HGH human growth hormone , and patches are claimed to have a genuine and enduring effect on women with sexual dysfunction, particularly those who are said to suffer from FADS, Female Androgen Deficiency Syndrome.
Lack of desire might well be down to hormones — in which case it’s worth checking it out, particularly if there has previously been no problem. But it can also be BWB syndrome (as in Bored with Bloke). There is no dispute about testosterone replacement in women who have had their ovaries removed completely before the menopause, and the inclusion of testosterone as part of their hormone replacement regimen is now considered important, particularly in maintaining libido.
Finally, science occasionally throws up those ‘no, never’ types of study. One, which received a great deal of publicity, was the Archives of Sexual Behavior study, published in 2002 , from a team at the State University of New York, which concluded that semen makes you happy. It compared women whose partners wore condoms, with women whose partners did not. Those who did use condoms were more depressed (their mood was assessed using a standard mood questionnaire called the Beck Depression Inventory). The time interval since their last protected encounter made no difference to their general misery. The non-condom users, on the other hand, were less depressed but the longer the interval since their last sexual encounter the worse their mood. The researchers concluded that this illustrated hormones at work – being absorbed from semen through the vaginal mucosa. Semen does indeed contain a cocktail of hormones, including, as you might imagine, testosterone, but also oestrogens, prolactin and a clutch of prostaglandins. However, there is somewhere between 8 and 80 picogrammes of oestradiol per millilitre of semen — which is a tiny amount.
This is the kind of research that scores a direct hit on your common-sense gene, and makes you say ‘yes, but what about …’. Perhaps women who used condoms were of a different personality type, or the ones who didn’t had more stable, sexually fulfilling relationships which made them happier. The researchers said that none of these factors could explain their findings. They claimed, less than convincingly, that men who made women feel happy were likely to have more chances to impregnate them, which would be biologically advantageous.
Does this mean, since some steroid hormones survive the digestion process, that oral sex is mood-enhancing ? Hmm… I wouldn’t count on it being on prescription as a replacement for Prozac in the near future. To be bold about this, you’d have to ship an awful lot of semen on board for it to make any real difference to your hormone levels. The andrologists that I consulted were unanimous. You get more oestrogen from one contraceptive pill than you would from – and their estimates varied -at least forty-three separate inseminations, assuming 5-12 ml per shot. Given that most (young) men can only run to half a dozen emissions a day, before temporarily running dry, you might want to find an alternative form of happiness therapy.