Microwave Man, that slightly old-fashioned, unreconstructed, domestically incapable but testosterone-fuelled single male, has an emotional, as well as physical, appeal to women. But Moisturised Man is a new phenomenon. A recent survey showed that men are now spending more on skin moisturisers, suntan lotions, bath oils and other skin products to appeal to women. Moisturised Man may also find that he has to do the washing-up and carry the shopping to succeed with the opposite sex.

The gender differences between male and female physique and behaviour have followed the pattern of pay cheques. And to reinforce the unisex society both are often dressed in jeans, and sweaters or T-shirts. The greater the outward similarity between the sexes, the greater is men’s need for more than testosterone when being appraised as a mate. Men need to be attractive mentally as well as physically, although the very rich or powerful can still play Don Juan, provided their testosterone levels are up to it. But the average man won’t get away with substandard looks and no sexual allure. The days when physically unattractive men were assured of a partner have followed the steam iron and laundry wringer into history.

Even so, men still need testosterone, the fuel for the reproductive male engine — without it, they will lack sexual charisma and however popular and however good as dinner party guests, they won’t climb the bedroom stairs later. Testosterone deficiency is not only associated with a low sex drive and varying degrees of impotence but it also results in loss of energy, tiredness, diminishing enthusiasm and organisational ability, as well as an older woman’s figure (an increasing waistband, larger breasts, a sagging bottom and thinner arms and legs). Furthermore, low testosterone is associated with anaemia and a greater liability to type 2 diabetes and its cardiovascular complications.

Recent research has shown that 20 per cent of men over 60 have a testosterone level below normal. The scientists considered that a serum testosterone level of less than 9.8 nanomoles per litre was below normal. British laboratories quote the normal range for testosterone as being 10 to 35.

However, Dr Richard Petty, who has a large West London practice specialising in problems of male sexuality, would consider anyone with a testosterone level of 9.8 to be seriously lacking in the hormone. In his opinion the average 60-year-old has a testosterone level of around 19, but that once a man’s testosterone level falls to between 11 and 16 he could display features of too little testosterone.

Dr Petty suggests that a man’s testosterone level should always be considered in relation to his age, otherwise young men might be deprived of necessary treatment.

Whatever a man’s age, the percentage of circulating testosterone that is in a form free to trigger a response in the testosterone receptors is alarmingly small. Most of the testosterone is bound to proteins, of which SHBG (sex hormone binding globulin) is the most important. Protein-bound testosterone is unavailable to give men their masculine characteristics. Unfortunately, although testosterone levels fall only by about a sixth between the ages of 25 and 60, their SHBG level almost doubles during the same period.

As a result, the greater a man’s age the less the amount of useful testosterone is circulating. Little surprise, therefore, that the size of a 60-year-old Don Juan’s girth has to be matched by that of his bank balance if he is to cut a dash on the beach.

The treatment of a low testosterone level requires experience, clinical acumen and a host of pathological tests. It was feared that boosting the testosterone levels with hormone supplements would increase arterial and coronary heart disease rate. The reverse has proved to be the case.

The association between testosterone and age seems to be determined by the rate of decline in testosterone levels rather than the actual level reached. Hence the desirability of knowing a man’s testosterone level at an earlier age. Another concern for doctors has been the effect of testosterone supplements on the risk of developing prostate cancer, which is associated with high testosterone levels. Great care is taken when assessing a man for hormone replacement therapy (HRT) of his liability to prostate cancer. There is follow-up of the man’s PSA, the blood test indicating the likelihood of malignant change. As yet, male HRT in older men has not been associated with a demonstrable increase of prostate cancer.