Primary Aldosteronism is the Most Common Cause of Secondary Hypertension
Primary aldosteronism (Conn syndrome) is definitively the most common cause of secondary hypertension, accounting for the largest proportion of identifiable secondary causes in adults. 1
Evidence Hierarchy
The 2024 ESC Guidelines explicitly state that "Primary aldosteronism (Conn syndrome) is the most common form of secondary hypertension" 1. This is corroborated by high-quality research demonstrating that primary aldosteronism causes more end-organ damage than essential hypertension and is associated with excess cardiovascular morbidity including heart failure, stroke, myocardial infarction, and atrial fibrillation 2.
Age-Dependent Variations
While primary aldosteronism dominates overall, the specific etiology varies by age group:
- Young adults (especially women): Renovascular hypertension from fibromuscular dysplasia is particularly common 3
- Middle-aged adults: Primary aldosteronism is the leading cause 3
- Older adults: Atherosclerotic renovascular disease becomes more prevalent 4
- Children: Renal parenchymal disease accounts for up to 85% of secondary hypertension cases 3
Other Common Secondary Causes
After primary aldosteronism, the frequency ranking includes:
Obstructive sleep apnea (OSA): Present in up to 60% of resistant hypertension patients 1. Some studies suggest OSA may be the most frequently detected condition when systematically screened, accounting for 24.7% of hypertensive patients in specialized centers 5
Renovascular hypertension: Affects 24% of older patients with resistant hypertension, with 35% of all secondary causes attributed to occlusive renovascular disease in specialty clinic populations 4
Renal parenchymal disease: Historically cited as accounting for 2.5-5% of all hypertension cases 6
Clinical Caveat
The apparent prevalence of secondary causes depends heavily on the population studied. In unselected hypertensive populations, secondary causes account for 5-10% of cases 3. However, in resistant hypertension cohorts seen at specialty centers, the detection rate jumps to approximately 40% 5. This discrepancy reflects both referral bias and the intensity of screening protocols employed.
Screening Implications
The 2024 ESC Guidelines recommend screening for primary aldosteronism using the aldosterone-to-renin ratio, with particular attention to prior potassium levels (hypokalaemia increases likelihood) 1. Despite primary aldosteronism being the most common and treatable cause, screening rates remain unacceptably low in clinical practice 2.
For OSA, validated questionnaires should be used in all resistant hypertension patients, particularly those with non-dipping patterns on 24-hour blood pressure monitoring or obesity 1. The high prevalence of OSA in resistant hypertension makes it a critical consideration, though whether it represents a true "cause" versus an exacerbating comorbidity remains debated 7.