Secondary hypertension
High blood pressure caused by an identifiable, often treatable, underlying condition — rather than the common 'essential' kind with no single cause. It is suspected when high blood pressure appears young, is very severe or hard to control, and is worked up with targeted blood, urine and imaging tests.
What it is
Most high blood pressure is 'essential' (primary) — it has no single identifiable cause and results from a mix of genetics and lifestyle. Secondary hypertension, by contrast, is high blood pressure caused by a specific, identifiable underlying condition, and it matters because treating that cause can improve or even cure the blood pressure. It accounts for a minority of cases, but the proportion is higher in certain groups. Common causes include kidney disease and narrowing of the kidney arteries; hormonal disorders such as primary aldosteronism (an overproduction of aldosterone, a leading and under-recognised cause), an overactive or underactive thyroid, Cushing's syndrome (excess cortisol) and a rare adrenaline-producing tumour (phaeochromocytoma); obstructive sleep apnoea; and certain medications and substances (including some painkillers, the contraceptive pill, decongestants, steroids and stimulants). Secondary hypertension is suspected when high blood pressure begins at a young age, is unusually severe or resistant to several medications, worsens suddenly, or comes with clues pointing to a specific cause — such as a low potassium (suggesting aldosterone excess) or episodes of sweating and palpitations. The work-up is targeted at the suspected cause and can lead to specific, effective treatment.
Key lab markers
- Potassium — a low level is a clue to primary aldosteronism.
- Aldosterone-to-renin ratio — screens for primary aldosteronism, a key treatable cause.
- Creatinine and eGFR, urinalysis — assess kidney disease as a cause and a consequence.
- Plasma or urine metanephrines — screen for a phaeochromocytoma.
- TSH, and cortisol tests — for thyroid disorders and Cushing's syndrome; imaging of the kidneys and adrenals as guided.
Symptoms
- Often the high blood pressure itself causes no symptoms
- High blood pressure that is severe, resistant to treatment, or starts young
- Clues to a cause: muscle weakness or cramps (low potassium)
- Episodes of headache, sweating and palpitations (phaeochromocytoma)
- Loud snoring and daytime sleepiness (sleep apnoea)
- Weight gain, easy bruising, round face (Cushing's syndrome)
- Symptoms of thyroid over- or under-activity
Related lab panels
When to discuss with a doctor
Secondary hypertension is worth looking for when high blood pressure has features that make a specific cause more likely: it begins at a young age, is very high, resists three or more medications, worsens abruptly, or comes with pointers such as an unexplained low potassium, spells of sweating and palpitations, or heavy snoring with daytime sleepiness. Finding and treating the cause can substantially improve or resolve the blood pressure, so this is a valuable work-up in the right person — usually guided by a doctor and sometimes a specialist. It does not replace controlling the blood pressure itself in the meantime. Mediora.AI can surface clues from your results — such as a low potassium or an abnormal aldosterone-to-renin ratio — that point toward a secondary cause worth investigating; the interpretation and any targeted testing belong with your doctor.