What are the common causes of hypertension ?

The various causes of hypertension include:

(1) Preeclampsia and eclampsia. The hypertension may be caused by a pressor polypeptide secreted by the placenta.

(2) Hyperaldosteronism and Cushing’s Syndrome produces hypertension due to salt and water retention.

(3) Pheochromocytomas. These are catecho- lamine-secreting tumors of adrenal medulla.

(4) Renal hypertension is due to narrowing of the renal arteries.

(5) Coarctation of the aorta, a congenital narrowing of a segment of the thoracic aorta, increases the resistance to flow, producing severe hypertension in the upper part of the body. The blood pressure in the lower part of the body is usually normal but may be elevated due to increased renin secretion.

(6) Pill hypertension. Oral contraceptives containing estrogens produces significant hypertension when consumed over prolonged periods. The hypertension is due to an increase in circulating levels of angiotensinogen, the production of which is stimulated by estrogens.

(7) Essential hypertension. This constitutes the largest group (90%) in which the cause is unknown. It is probably due to autonomic hyperreactivity so that there are exaggerated hypertensive responses to stimuli such as cold and excitement. The frequent spasms of the arterioles lead to hypertrophy of their musculature so that at later stages, the hypertension becomes sustained.