Manpower?

decreasing sperm count and infertility in recent years may have not much to do with chemicals that mimic female hormones in the environment. Recent research shows that sperm actively needs female hormones, oestrogen, to mature fully, thrive and function effectively ( Nature , Vol 390, No 6659).

Ever since sex hormones were discovered, oestrogen have been regarded as intrinsically female hormones and androgens such as testosterone, the essence of masculinity. Oestrogen regulate the menstrual cycle in women and cause the changes associated with the transition of a girl into a woman through associated physiological changes.

Limited changes can be induced in the opposite sex by administering these hormones. However, men and women naturally produce small quantities of both hormones, and scientists believe that they are "two sides of the same coin" in regulating many body functions. It is now known that some important physiological functions in both sexes are governed by the same hormone. It is oestrogen, for instance, that determines the growth of bones. This essential role of oestrogen has been under scrutiny for sometime, especially its role in fertility in males. About 300 million sperms are made daily inside every adult human male, within roughly 250 metres of somniferous tubules coiled up inside each testis. The immature sperm fluid, also produced by the tubules, flows into a collecting area and into a convoluted sac called kaput epididymis. This is sensitive to oestrogen. A team from the University of Illinois, usa, reports that genetically engineered mice that have no cells in the epididymis are sterile. As the dilute sperm solution enters the epididymis, about 90 per cent of the fluid is resorbed. Rex Hess and his colleagues found that a particular oestrogen hormone called oestradiol is vital to the process of fluid resorption.

Disruption of this essential function causes sperm to enter the epididymis in a diluted rather than a concentrated form resulting in infertility. Dilution of sperm fluid reduces the chances of sperms reaching the egg. But these sperms suffer another disadvantage -- the chemicals and nutrients that it needs to mature are also diluted. Eventually, the accumulation of unresorbed fluid damages the testes. There has been a steady and significant reduction of sperm count in the industrial world, which has been attributed to increase in pollutants, especially 'oestrogen mimics'. But recent research has shown that both male and female hormones share a role in fulfilling the same tasks in both sexes. In the developing human embryo, for instance, these hormones decide whether it is going to be a boy or a girl. During puberty, they control development to full sexual maturity and go on to influence the sexual behaviour of adults.

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