Secondary Hypertension

About 5 to 10 percent of patients with high BP have secondary HTN. By definition, secondary HTN has an identifiable and potentially correctable cause (Table 1).13 Whenever a patient is diagnosed with high BP, one purpose of the initial assessment (i.e., history, physical examination, and basic laboratory testing) is to identify possible secondary causes. The dietary habits and medication profile is also assessed. Excessive consumption of sodium, licorice, and alcohol is known to increase the BP. Agents such as estrogen (e.g., oral contraceptives), herbals and supplements (e.g., ephedra, ginseng, and ma huang), illicit drugs (e.g., amphetamines and cocaine), NSAIDs, CNS drugs (e.g., buspirone, carbamazepine, clozapine, fluoxetine, lithium, and tricyclic antidepressants), steroids, and sympathomimetic agents (e.g., decongestants and diet pills) may also affect BP.

Table 1. Common Age-based Identifiable Causes of Hypertension.
Age Group % of Hypertension with an Identifiable Cause Common Etiologies
Birth to 12 years 70 to 85% Coarctation of the aorta
Renal parenchymal disease
13 to 18 years 10 to 15% Coarctation of the aorta
Renal parenchymal disease
19 to 39 years 5% Fibromuscular dysplasia
Renal parenchymal disease
Thyroid dysfunction
40 to 64 years 8 to 12% Aldosteronism
Cushing syndrome
Pheochromocytoma
Sleep apnea
Thyroid dysfunction
≥65 years 17% Atherosclerotic renal artery stenosis
Hypothyroidism
Renal failure

The most recent American College of Cardiology/American Heart (ACC/AHA) Association Task Force on Clinical Practice Guidelines for BP management introduced a more conservative threshold for hypertension (Figure 3).14 As a consequence, the number of patients with HTN has increased from 32 percent to 46 percent (68 million to 103 million) of adults 18 years and older in the United States.15 The risk of developing HTN varies by race and increases dramatically with age. For adults 45 years of age without HTN, the 40-year risk of developing HTN was 93% for African-American, 92% for Hispanic, 86% for white, and 84% for Chinese adults.

Figure 3. Classification of blood pressure for adults aged 18 or older.12
  SBP   DBP
Normal <120 mm Hg and <80 mm Hg
Elevated 120–129 mm Hg and <80 mm Hg
Hypertension      
Stage 1 130–139 mm Hg or 80–89 mm Hg
Stage 2 ≥140 mm Hg or ≥90 mm Hg

Only 30% of adults with HTN are aware of their condition and only about 60% of those diagnosed with HTN are receiving antihypertensive therapy.16