Renin in essential hypertension

Acromegaly and hypertension: prevalence and relationship to the renin-angiotensin-aldosterone system

The prevalence of arterial hypertension was evaluated in a retrospective study of 158 patients with acromegaly, and results were compared to control populations, namely, the Munich Blood Pressure Study (MBPS) and the Framingham Study. The prevalence of hypertension (defined according to WHO criteria) was significantly increased in female patients but not in men; hypertensive acromegalics were older and tended to have higher body weight compared to normotensive patients. Hypertension was not related to serum concentrations of growth hormone. After successful treatment of acromegaly, growth hormone levels and systolic and diastolic blood pressure fell only in female hypertensive acromegalics; this did not occur in normotensives. The rise in plasma renin activity in response to upright posture was diminished in 57.9% of acromegalic patients. The prevalence of low-renin hypertension in our group of patients was 31.6%, which is similar to figures reported for unselected non-acromegalic subjects with essential hypertension. Orthostatic renin activity was weakly and inversely related (r = -0.3) to blood pressure. No relationship between plasma aldosterone concentration and blood pressure could be detected; however, in acromegalic women, aldosterone rose higher after ambulation than in men. In conclusion, hypertension is a common problem in acromegaly and at least in part related to similar risk factors in control populations. The association with abnormalities of the renin-angiotensin-aldosterone system is difficult to interpret and does not offer an explanation for the slight increase in the prevalence of hypertension.

Angiotensin-converting enzyme and its clinical significance--a review

There have been considerable advances in understanding the metabolic role of the endothelial lining cells of the blood vessels. Angiotensin-converting enzyme activity is concentrated in these cells, especially those lining the pulmonary circulation. The enzyme exerts control over systemic vascular tone indirectly through the powerful pressor effect of angiotensin II. A number of therapeutic agents are now available which directly inhibit converting enzyme activity and thereby effect a reduction in blood pressure. Macrophages are the source of increased angiotensin-converting enzyme activity commonly found in association with active sarcoidosis. A better understanding of this phenomenon may give fresh insight into this puzzling condition. Pulmonary endothelial metabolism is affected by lung injury and it is likely that in this situation changing activities of serum angiotensin converting enzyme may indicate the extent of damage and the response to therapy. The full clinical significance of serum ACE measurements has yet to be established. However, raised activities have been reported in a number of other conditions and diabetes mellitus and hyperthyroidism are of particular current interest. The numerous methods and reference ranges described in the literature for the measurement of serum ACE activity require further assessment, and there is a clear need for an accepted reference method.