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Is there a link between human hormones and sexual desire? According
to the latest study of the hormone testosterone, the answer is no (Physiology
and Behavior, vol 52, p 195).

Psychologists James Dabbs and Suzanne Mohammed of Georgia State University
in Atlanta studied the affect of testosterone on libido. Four established
heterosexual couples in their 20s participated in their study.

Dabbs and Mohammed noted that taking blood samples to analyse hormone
levels ‘may interfere with coitus’. So instead they measured the level
of ‘free’ testosterone in a teaspoon-sized sample of each person’s saliva.
Participants in the study were given chewing gum to enhance the amount of
saliva they produced.

Over about eight days, the subjects collected one saliva sample after
dinner and another before going to sleep, and stored them in the freezer.
On the pre-sleep sample they were asked to mark whether they had made love
in the interim.

According to Dabbs and Mohammed, there were problems in collecting the
data, ‘with subjects forgetting to collect samples or not engaging in coitus
any evening, or every evening, or the wrong time of evening (before the
first saliva sample)’. But in the end the researchers managed to collect
samples with an average of three ‘sex’ and three ‘nonsex’ days for each
subject.

The researchers discovered that the hormone levels in the early evening
did not differ on the sex and nonsex days – squashing the notion that higher
testosterone levels might ’cause’ people to indulge in sexual intercourse.
But the researchers found that once men and women had made love, their testosterone
levels were higher than they had been earlier in the evening.

Even running raises testosterone levels briefly in both sexes. But the
study cannot address the ‘exercise factor’ because it did not control for
the time between sex and the taking of the saliva sample. But the psychologists
tried to minimise this difficulty: ‘The exercise in coitus, variously described
in interviews with our subjects as like wrestling, bike riding, horseback
riding, doing push-ups, and like nothing else, does not seem to us intense
enough to have produced increasesintestosterone.’

They point to their finding that testosterone levels after sex were
7 per cent higher for men and 42 per cent higher for women than the late-night
concentrations on nonsex nights. They conclude that ‘at least for females,
sex is more arousing than riding a bicycle’.