There is an intimate relationship between diabetes mellitus (DM) and hypertension. It is estimated that if diabetic patients live long enough, approximately 75% will develop hypertension. The following mechanisms mediate the development of hypertension in diabetes:
- Activation of the tissue-based renin-angiotensin-aldosterone axis;
- Volume expansion secondary to hyperglycemia;
- Reduced baroreceptor response;
- Autonomic dysfunction (exaggerated orthostatic response and loss of circadian rhythm without the normal nighttime depression in blood pressure);
- Endothelial dysfunction and vascular oxidative stress.
Hypertension is more difficult to control in diabetic patients than in non-diabetic patients. Several published studies corroborate the need for multiple antihypertensive agents – on average, three – to achieve target blood pressure goals in this population.
In addition, increasing systolic blood pressure portends even greater increases in mortality in diabetic patients than in non-diabetic patients; and even at normal blood pressure, the risk for cardiovascular death is 25-fold greater.
Hypertension can be classified as either essential (primary) or secondary. Essential hypertension indicates that no specific medical cause can be found to explain a patient’s condition. Secondary hypertension indicates that the high blood pressure is a result of (i.e. secondary to) another condition, such as kidney disease or certain tumors (especially of the adrenal gland). Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure and arterial aneurism, and is a leading cause of chronic renal failure.
Over 91% of adult hypertension has no clear cause and is therefore called essential/primary hypertension. Often, it is part of the metabolic “Syndrome X” in patients with insulin resistance; it occurs in combination with diabetes mellitus (type-2), combined hyperlipidemia and central obesity.
Secondary obesity is more common in preadolescent children, with most cases caused by renal disease. Primary or essential hypertension is more common in adolescents and has multiple risk factors, including obesity and a family history of hypertension.