What is secondary hypertension?

by 60888888 on 2010-02-01 14:08:39

I have already talked to everyone about primary hypertension, and today I will continue to discuss the causes of secondary hypertension. Secondary hypertension refers to hypertension that is secondary to other diseases or causes. It only accounts for 5% to 10% of the population with hypertension. Elevated blood pressure is only one of the clinical manifestations of these diseases. The clinical manifestations, complications, and consequences of secondary hypertension are similar to those of primary hypertension.

What are the causes of secondary hypertension?

1. Renal Hypertension

Renal hypertension is the most common type of secondary hypertension. It is caused by vascular or parenchymal lesions in the kidneys. When the renal artery responsible for supplying blood to the kidneys becomes narrowed, it leads to ischemia in the kidney, and one of the main clinical manifestations is hypertension. Common renal parenchymal lesions causing high blood pressure include nephritis, chronic pyelonephritis, renal nuclei, systemic diseases such as kidney damage from systemic lupus erythematosus, etc. Patients with renal parenchymal lesions often exhibit hypertension clinically, and abnormal findings such as protein, white blood cells, or red blood cells can be detected in urine tests.

2. Hypertension Caused by Adrenal Disorders

The small glands above the kidneys - the adrenal glands - their hyperplasia or tumors are also an important cause of secondary hypertension. The outer layer of the adrenal gland is the cortex, and the middle layer is the medulla. Hyperplasia or tumors in the adrenal cortex mainly lead to two conditions: Cushing's syndrome and primary aldosteronism. In patients with Cushing's syndrome, the adrenal cortex excessively secretes a substance called glucocorticoid hormones.

Besides having hypertension, patients often exhibit centripetal obesity, muscle wasting in the limbs, a moon-shaped face (called a full moon face), flushed complexion (plethora), purple streaks on the abdomen and inner thighs, acne, increased body hair, irregular menstruation, and varying degrees of masculinization in women. Patients who take cortisone, dexamethasone, and other drugs for long periods due to other diseases may also exhibit this set of clinical symptoms. The clinical manifestations of Cushing's syndrome are characteristic, making it generally not difficult to differentiate from primary hypertension.

In primary aldosteronism, the excessive substance secreted by the adrenal cortex hormone is aldosterone. Excessive aldosterone leads to water and sodium retention in the body while increasing potassium excretion through urine. Besides elevated blood pressure, blood tests reveal hypernatremia and hypokalemia, and urine tests show increased urinary potassium but less sodium excreted through urine than consumed in the diet. Due to low blood potassium, patients experience fatigue, muscle weakness, intermittent paralysis, and cramps. Frequent nocturia is also a common symptom. Adrenal medullary diseases causing secondary hypertension include pheochromocytoma. The adrenal medulla intermittently or continuously secretes excessive adrenaline or noradrenaline. These substances increase heart rate, constrict blood vessels, and cause episodic or sustained increases in blood pressure. The three common symptoms are episodic severe headaches, sweating, and palpitations. However, they may not all appear simultaneously in one patient. Other symptoms include pallor, nausea, abdominal pain, and breathing difficulties.

3. Pregnancy-induced Hypertension Syndrome (PIH)

There are roughly three scenarios for elevated blood pressure in pregnant women:

① Pregnant women already had primary or secondary hypertension before pregnancy, referred to as chronic hypertension complicating pregnancy;

② Hypertension appears during pregnancy, and blood pressure returns to normal within three months after delivery, which is known as pregnancy-induced hypertension syndrome;

③ Pregnant women already had existing hypertension; after pregnancy, the increase in blood pressure worsens, termed pre-pregnancy hypertensive condition complicated by PIH.

The diagnosis of PIH is generally not difficult. PIH patients often exhibit edema, and urine tests reveal increased protein levels, i.e., proteinuria.

4. Vascular Hypertension

Vascular lesions that cause elevated blood pressure commonly include coarctation of the aorta, Takayasu arteritis, and atherosclerosis. In patients with coarctation of the aorta, blood pressure in the upper limbs significantly increases, while blood pressure in the lower limbs is low, or even absent. Takayasu arteritis mostly affects young women and often involves arteries on one side of the body. When measuring blood pressure, significant differences in blood pressure between the two upper limbs can be found, with one side abnormally elevated and the other side low or even unmeasurable. Takayasu arteritis can also affect the renal arteries, leading to renal artery stenosis. Atherosclerosis, common in elderly people, can also cause significant differences in blood pressure between the two upper limbs.