Endocrine Abstracts

Hypertension and diabetes are prevalent conditions. Population studies suggest that blood pressure in excess of 140/90 mmHg is found in nearly 30% of adults while type 2 diabetes occurs in 3-4%. However, both conditions are strongly age-dependent, and exhibit large geographical variations. Non-european populations typically have much higher prevalence rates. Worldwide, there has been a dramatic increase in the occurrence of type 2 diabetes. It has long been known that these conditions tend to occur together in the same patients; approximately 2/3 of diabetics will have hypertension while hypertensive subjects have a substantially increased risk of diabetes. Both conditions are, in turn, associated with other metabolic abnormalities including dyslipidaemia (raised plasma triglyceride and low high density lipoprotein concentrations)and central or abdominal obesity. This cluster of conditions which is known as the metabolic syndrome is associated with a substantially increased risk of cardiovascular disease.

The aetiological mechanisms underlying the development of hypertension and diabetes and the reasons for their clustering are still not understood. Resistance to the metabolic actions of insulin and consequent hyperinsulinaemia seem to play a central role as all the conditions comprising the metabolic syndrome are strongly associated with insulin resistance. In prospective studies insulin resistance predicts many of the components of the syndrome. Although there is agreement that obesity coupled with a sedentary lifestyle is an important preventable cause, the other factors involved in the pathogenesis of the metabolic syndrome or its components are still a subject of debate. While genetic factors are likely to be involved, progress in identifying these has been slow. The demonstration that type 2 diabetes, hypertension and some other features of the metabolic syndrome are related to low birthweight has raised the possibility that the conditions may arise as a result of altered intrauterine development. Current thinking suggests that a complex interaction between hereditary factors, developmental processes and adult lifestyle will explain the aetiology of these conditions.