When women reach menopause, their hormones hit the brakes hard. Hormonal changes in middle-aged men are less drastic. Their bodies' production of testosterone, the main male sex hormone, declines gradually.
This is why many experts reject the term "male menopause," or "andropause", for members of the stronger sex, who have just had the best years of their lives.
"Age-related hypogonadism" would be an apter description, according to Professor Sabine Kliesch, a urologist at Muenster University Hospital in Germany and spokesperson for the German Society of Andrology (DGA).
"Men's testosterone production decreases with advancing age," said Kliesch, who cited studies showing that testosterone levels in affected men's blood fall by about 0.4 per cent a year. Certain ailments that occur more frequently with age can also lower testosterone levels, however, including fat- and sugar-metabolism disorders as well as cardiovascular diseases and tumours.
Reduced testosterone levels usually affect men after the age of 45 or 50 and are more likely if the aforementioned ailments are present. The drop can manifest itself in various ways. While typical symptoms are not necessarily due to a testosterone deficiency alone, there is often at least a partial connection.
"A very sensitive early-warning system is diminished libido," Kliesch noted. Fatigue, insomnia, difficulties concentrating, and a lack of drive also point to possible hormonal changes, whose effects include reduced muscle mass and bone density.
"There's a fluid boundary between what's normal and what's a medical condition," Kliesch said. When medical specialists are deciding whether to treat a man with hormones, they prefer to go by hard facts rather than the soft symptoms named earlier. A true testosterone deficiency affects bone metabolism and blood formation, for example.
"Therapy is needed only when a man has a laboratory-proven testosterone deficiency and - this is very important - clinical symptoms of a deficiency," Kliesch said.
Her colleague Harald Klein, a professor at Germany's Bochum University and spokesman for the German Society of Endocrinology (DGE), concurred. Declining testosterone levels with advancing age is not a disorder per se, he said, noting that the key question was whether the levels were normal or pathological.
"Should a young man lose his testicles, there's no question that testosterone therapy is necessary," Klein remarked.
If the responsible physician is certain that a pathological testosterone deficiency is present, only one remedy is available: the controlled replacement of the hormone until its levels in the blood are normal for a man that age.
Before beginning treatment, the physician must check to see whether the patient has a condition that definitely rules out the use of testosterone. The first is prostate cancer. Another is breast cancer - rare in men. There are also relative contraindications, which do not necessarily rule out testosterone treatment: excessive red blood cell formation, for example, or sleep apnea, a disorder characterized by pauses in breathing during sleep.
In the view of Walter Trettel, an anti-aging physician from Hamburg, administering testosterone is not the only way to treat the discomforts of "male menopause." He uses oestrogen and progesterone. Although both are known as female sex hormones, men's bodies produce them in small amounts too.