Handbook of Diabetes, 4th Ed., Excerpt #18: Hypertension in Diabetes

Diagnosis of hypertension

Patients should have blood pressure measured in a standardized way with readings above 140/90 mmHg on at least two occasions before they are diagnosed with hypertension (Box 19.3). Ambulatory blood pressure or home assessment can be used in cases of doubt but diagnostic readings in these circumstances are 10/5 mmHg lower (120/75 mmHg). Initial management should include a thorough basic examination and investigations (Box 19.4).

Management

Lifestyle changes can be remarkably effective. Table 19.1 lists those known to have an impact on blood pressure but most of these data have been gleaned from populations without diabetes or from mixed populations with and without type 1 and type 2 diabetes.
Some drugs and behaviors are known to increase blood pressure (Box 19.5).

Hypertension is a feature of endocrinopathies that also cause glucose tolerance such as Cushing’s syndrome, acromegaly and pheochromocytoma. These rare conditions should be considered and excluded (see Chapter 8).

Drug treatment

Lifestyle changes should be tried for at least 3 months before commencing medication. However, if blood pressure is > 20/10 mmHg above target, drug treatment should be started immediately, and will usually require two agents initially.

Drugs which block the RAS

The RAS has been closely linked to the development of micro- (particularly nephropathy) and macrovascular complications. Activation both locally at the tissue level and systemically has been described in people with diabetes. Angiotensin II (AII) is a potent vasoconstrictor and has profibrogenic properties in both the kidney and myocardium. Aldosterone causes salt and water retention and is also profibrogenic. Moreover, several of the breakdown products of angiotensin I (AI) and II have vasoactive properties and our understanding of the RAS shows it to be much more complicated than originally realized. The rate-limiting step for AII production from the RAS is renin activation. Although renin is an enzyme, together with its precursor prorenin it now appears to have its own receptor (Figure 19.3).