Adult females make it themselves out of cholesterol converted by their gonads and their adrenal cortex first into progesterone, then into testosterone and then into estrogen. The ovaries carry on producing estrogen long after ovulation has ceased, more than twelve years in fact. The adrenal glands atop the kidneys produce estrone to boost it; all steroid hormones are lipophilic, that is, soluble in fats and easily diffused through membranes. They bind with intracellular receptor proteins and the resultant complex binds to DNA. The scale of effects of this process is as yet hardly glimpsed. What we know and are prepared to say is that ‘estrogen lifts our moods and gives us a feeling of well-being’. It probably does that by influencing some of the neuropeptide transmitters in the brain that regulate how we feel and think, probably oxytocin and vasopressin, together with the enkephalins and dynorphins, opioids produced in the brain.

Oxytocin is particularly interesting not only because it can be shown to have specific functions connected with arousal and orgasm in both males and females, but because neurons containing oxytocin receptors have been found in regions of the brain that suggest a role in bonding behavior. Such data might give the impression that personality is a simple bio-chemical cocktail and can be changed just by upping some part of the mixture. In fact the cocktail has some 4,000 elements that are continually being shaken and stirred; the overall and ultimate effects of adding a jigger of something new are unknowable.

The sex hormones estrogen and progesterone are closely related to anabolic steroids and, like them, affect mood and behavior. People suffering disruptions of their normal biochemical balance will report personality disturbances. The behavioral effects of added estrogen are difficult to quantify; estrogen will not increase libido, for example, as it exerts little action on the clitoris, but it does increase receptivity in that it controls the vaginal environment.

We know enough to know that sex steroids are powerful and that they have complex interactions with other substances, which would seem to be good reason not to introduce similar substances that would replicate or exaggerate or annihilate any part of the wonderfully intricate sequence. In the case of recreational drugs reasonable people are only too ready to accept the idea that interference is foolhardy; when it comes to exogenous estrogen, which is a drug like any other, we are suddenly undisturbed by the prospect of lifelong dependency. Estrogen is now being tried and found effective as a mood-altering substance; it has been used successfully as a symptomatic treatment for severe post-natal depression.