What are the causes of secondary hypertension?

Causes of Secondary Hypertension

Secondary hypertension affects 5-10% of hypertensive patients, but prevalence increases to approximately 20% in resistant hypertension cases. 1 Understanding the underlying causes is essential for effective management and potential cure of hypertension.

Common Causes of Secondary Hypertension

Renal Causes

• Renal parenchymal disease - one of the most common causes 2, 3
• Renovascular disease:
  • Atherosclerotic renal artery stenosis (more common in older adults) 3
  • Fibromuscular dysplasia (more common in younger patients) 1

Endocrine Causes

• Primary aldosteronism - occurs in 5-10% of hypertensive patients and up to 20% of patients with resistant hypertension 4, 1
• Pheochromocytoma/paraganglioma - rare but important cause 2, 3
• Cushing's syndrome - characterized by truncal obesity, purple striae 5, 6
• Thyroid disorders - both hyperthyroidism and hypothyroidism 2, 3
• Hyperparathyroidism - associated with hypercalcemia 5
• Acromegaly - characterized by acral features, enlarging shoe/glove/hat size 4
• Congenital adrenal hyperplasia - rare cause 2

Sleep Disorders

• Obstructive sleep apnea - common but often overlooked cause 1, 3

Vascular Causes

• Coarctation of the aorta - important cause especially in children and young adults 5, 3

Medication and Substance-Related Causes

• Medications that can cause or exacerbate hypertension 4, 1:

  • NSAIDs
  • Oral contraceptives
  • Sympathomimetics
  • Corticosteroids
  • Immunosuppressants (e.g., cyclosporine)
  • Angiogenesis inhibitors and tyrosine kinase inhibitors
  • Antidepressants (e.g., MAOIs, SNRIs, TCAs)
  • Atypical antipsychotics
  • Decongestants

• Substances:

  • Alcohol
  • Caffeine
  • Recreational drugs (cocaine, amphetamines, etc.)
  • Herbal supplements (e.g., Ma Huang [ephedra], St. John's wort)

Clinical Indicators Suggesting Secondary Hypertension

• Early onset hypertension (before age 30, especially before puberty) 5, 3
• Late onset hypertension (after age 50) 5
• Severe or resistant hypertension (requiring >3 medications) 1, 5
• Sudden deterioration in previously controlled blood pressure 1
• Hypertensive urgency or emergency 1
• Target organ damage disproportionate to hypertension duration or severity 1
• Specific physical findings (e.g., abdominal bruits, decreased femoral pulses) 5
• Laboratory abnormalities (e.g., hypokalemia, hypercalcemia, hyperglycemia) 5

Diagnostic Approach

Basic Screening Tests

• Blood tests: electrolytes, renal function, glucose, lipids, TSH, calcium 1
• Urine tests: urinalysis, albumin-to-creatinine ratio 1
• 12-lead ECG 1

Specific Screening Tests

• Plasma aldosterone/renin ratio for primary aldosteronism 1
• Renal ultrasound for renal parenchymal disease 1
• Renal Duplex Doppler for renovascular disease 1
• Sleep studies for obstructive sleep apnea 1

Management Considerations

Treatment should target the underlying cause:

• For primary aldosteronism: adrenalectomy for unilateral disease, mineralocorticoid receptor antagonists for bilateral disease 1
• For renovascular disease: medical therapy or angioplasty depending on the cause and renal function 1
• For obstructive sleep apnea: weight loss, CPAP, mandibular advancement devices 1
• For medication-induced hypertension: discontinue or reduce offending agents 1

Common Pitfalls to Avoid

• Failing to screen appropriate patients for secondary causes 1
• Continuing medications that contribute to hypertension 1
• Inadequate dosing of diuretics in resistant hypertension 1
• Not referring complex cases to specialists 1
• Overlooking dietary factors like excessive sodium intake and licorice consumption 1

Remember that early identification and treatment of secondary causes can lead to improved blood pressure control and potentially cure hypertension in some cases, significantly reducing cardiovascular morbidity and mortality.