From the Guidelines
Primary hypertension and secondary hypertension differ primarily in their underlying causes, with primary hypertension being the most common form, accounting for about 90-95% of all hypertension cases, and secondary hypertension being caused by an identifiable underlying condition, accounting for approximately 5-10% of hypertension cases. The key difference between the two is that primary hypertension develops gradually over many years without an identifiable cause, likely resulting from a complex interaction of genetic factors, lifestyle choices, and environmental influences 1. On the other hand, secondary hypertension is caused by an identifiable underlying condition, such as kidney disease, adrenal gland tumors, thyroid problems, certain medications, sleep apnea, and congenital blood vessel defects 1.
Key Characteristics of Primary and Secondary Hypertension
- Primary hypertension:
- Develops gradually over many years
- No identifiable cause
- Accounts for about 90-95% of all hypertension cases
- Likely results from a complex interaction of genetic factors, lifestyle choices, and environmental influences
- Secondary hypertension:
- Caused by an identifiable underlying condition
- Accounts for approximately 5-10% of hypertension cases
- Can be caused by kidney disease, adrenal gland tumors, thyroid problems, certain medications, sleep apnea, and congenital blood vessel defects
- Tends to appear suddenly and cause higher blood pressure than primary hypertension
Screening for Secondary Hypertension
When evaluating a patient with hypertension, especially if they are young, have sudden onset of severe hypertension, or are not responding to standard treatments, clinicians should consider screening for secondary causes 1. The 2020 international society of hypertension global hypertension practice guidelines recommend considering screening for secondary hypertension in patients with early onset hypertension, resistant hypertension, sudden deterioration in BP control, hypertensive urgency and emergency, and those presenting with high probability of secondary hypertension based on strong clinical clues. Basic screening for secondary hypertension should include a thorough assessment of history, physical examination, basic blood biochemistry, and dipstick urine analysis.
Clinical Implications
Treating the underlying cause of secondary hypertension can often cure the high blood pressure, while primary hypertension typically requires lifelong management through lifestyle modifications and medication. Clinicians should be aware of the differences between primary and secondary hypertension and consider screening for secondary causes in patients with hypertension, especially if they are young, have sudden onset of severe hypertension, or are not responding to standard treatments. By identifying and treating the underlying cause of secondary hypertension, clinicians can improve patient outcomes and reduce the risk of cardiovascular disease.
From the Research
Definition and Prevalence
- Primary hypertension (HTN) is also known as essential hypertension, and its cause is unknown 2.
- Secondary hypertension, on the other hand, has an identifiable and potentially reversible cause, accounting for 5-10% of all hypertension cases 2, 3, 4, 5, 6.
Causes of Secondary Hypertension
- Renal parenchymal disease and renovascular diseases are common causes of secondary hypertension 2, 3, 4, 5, 6.
- Other causes include coarctation of the aorta, Cushing's syndrome, primary hyperaldosteronism, pheochromocytoma, hyperthyroidism, and hyperparathyroidism 2, 3, 4, 5.
- Additionally, obstructive sleep apnea, drug and substance use, and certain medications can also lead to secondary hypertension 3, 4, 6.
Diagnosis and Evaluation
- Features that aid in the diagnosis of secondary hypertension include onset of hypertension before the age of 20 or after the age of 50 years, markedly elevated blood pressure, and specific body habitus and ancillary physical findings 2.
- Resistant or refractory hypertension, specific biochemical tests, and abdominal diastolic bruits are also indicative of secondary hypertension 2, 3, 6.
- A combination of a good history and physical examination, astute observation, and accurate interpretation of available data usually are helpful in the diagnosis of a specific causation 2.
Management and Treatment
- Correct diagnosis of a causative underlying condition can lead to more effective, even curative management and subsequent cardiovascular risk reduction 4.
- Management involves treating the underlying condition, and some patients may benefit from referral to a specialist with specific expertise in treating the causative condition 4, 6.