Endocrine Abstracts

For years it was thought that the excess male mortality compared to age-matched females was explained by unhealthy behaviours that were more acceptable for men, and not the inherent sex differences in biology. The intention of this review is to illustrate whether it is our environment, hormones or genes that really make the sexes different in terms of the cardiovascular system. My focus will be on the genetic difference between men and women, in particular, the Y chromosome, and how this could be a risk factor for males.

Environment: Behavioural mechanisms combine to render men are at higher risk of cardiovascular disease. Factors such as smoking and lower levels of physical activity are thought to play a crucial role in obesity, diabetes and cardiovascular disease. However, recent studies adjusting for unhealthy behaviours show that they contribute to but do not fully explain the increased risk of CHD in men.

Hormones: The most frequent explanation put forward by experts to explain the gender gap in CHD risk is that women are relatively protected due to their high levels of endogenous oestrogen whereas androgens, which are higher in men, may be harmful. However, several observations go against a major role for endogenous oestrogen or androgens.

Genes on sex chromosomes: Human sex chromosomes determine our sexual phenotype during foetal life. Most of the male determining Y chromosome (the smallest human chromosome) does not recombine with the X chromosome. Human studies have shown that a mutation(s) of a locus on the Y chromosome maybe partially responsible for increase in blood pressure and lipids in males.

In summary, I like to propose that all the above three affect our cardiovascular system, but I also like to be controversial and say that genes are likely to be the most important.