A popular line of research has been to examine the effects of environment and lifestyle on health and wellbeing. Over the past few years, for example, reports of male reproductive abnormalities have increased, so it begs the question why?
A recent study, published in the journal Endocrinology, suggests that a combination of stress and exposure to certain chemicals may increase the likelihood of certain disorders including undescended testicles (cryptorchidism), misaligned urinary tracts (hypospadias) and reduced sperm count, collectively linked to a syndrome called testicular dysgenesis syndrome (TDS). Mandy Drake and colleagues from Edinburgh University, examined the effect of a stress hormone combined with a chemical commonly found in plastics, glues and paints.
Although reproductive disorders are mainly seen after exposure to abnormally high levels of chemicals, Drake, reported by the BBC news website, suggests that, "additional exposure to stress, an everyday event, may increase the risk of these disorders and could mean that lower levels of chemicals are required to cause adverse effects."
The research team examined how conditions in the womb affected the development of male rats. Some pregnant rats were injected with varying levels of solvents used to soften plastics such as shower curtains, toys, credit cards and vinyl flooring. Rats were separated into six groups where two were given a daily dose of chemicals, three were injected with the stress hormone dexamethasone, either alone or in combination with chemicals, and the sixth group acted as the experimental control.
When the male rats were born they were checked for physical defects. The results revealed that the control group had no physical defects. Of the rats that received only the stress hormone, 3 percent had undescended testicles. Of the 45 rats that received low dose chemicals, none showed any physical defects. In the 35 rats that received high levels of chemicals, 53 percent had undescended testicles and 31 percent hypospadias. In the group of rats that received high levels of chemicals and the stress hormone, 86 percent had undescended testicles and 45 percent had hypospadias.
What do such studies tell us? Well, animal research like this does seem to demonstrate that a combination of stress and exposure to toxins can have a critical effect on later development. The effect of exposure to toxins and subsequent birth defects is well established, but the role of stress in the mix is far from understood. In relation to this specific study what remains unclear is whether exposure to dibutyl phthalate (DBP) - the chemical used - would have any such effect on the human fetus.
We also need to ask whether the injection of a synthetic hormone to stimulate stress is a suitable platform from which to suggest a relationship with the human condition? What this study shows is that stress, as defined by the introduction of the stress hormone dexamethasone, had a negative effect but in real terms the most significant damage still appears to have been done by the introduction of high doses of chemical toxins. The view that higher levels of stress combined with lower levels of environmental toxins could be equally damaging is interesting but is something that requires more time and careful study.
Drake. A.J., van den Driesche. S., Scott, H.H., Hutchison, G.R., Seckl, J.R., and Sharpe, R.M (2009) Glucocorticoids Amplify Dibutyl Phthalate-Induced Disruption of Testosterone Production and Male Reproductive Development. Endocrinology, Nov; 150: 5055 - 5064.
NHS Choices. Stress, Plastics and Male Infertility. http://www.nhs.uk. Accessed 11.16.2009.
Published On: November 16, 2009