Secondary arterial hypertension , definition,causes, pathophysiology, symptoms, diagnosis, differential diagnosis, treatment with doses

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Secondary Arterial Hypertension

Definition

Secondary arterial hypertension is hypertension associated with a specific, identifiable anatomic or biochemical cause — and is therefore potentially curable if that cause is removed or corrected. This distinguishes it from primary (essential) hypertension, which has no single identifiable cause.

Secondary hypertension accounts for approximately 10% of all hypertension in adults. Among children, secondary causes are the rule rather than the exception — up to 90% of young children with hypertension have an identifiable secondary cause.

When to suspect secondary hypertension:

Treatment-resistant hypertension (BP uncontrolled on ≥3 drugs)
Abrupt onset or worsening of hypertension
Hypertension in patients <30 years
Disproportionate target-organ damage for the level of BP
Unprovoked hypokalemia, proteinuria, or LV hypertrophy on workup

— Harrison's Principles of Internal Medicine 22E, p. 2179

Causes

The main causes in approximate order of prevalence in adults:

Cause	Estimated Prevalence Among Hypertensives
Obstructive Sleep Apnea (OSA)	Most common; >30% of hypertensives
Medication/substance-induced	Very common; >26% use NSAIDs alone
Renal parenchymal disease (CKD)	~5% of non-OSA secondary HTN
Primary aldosteronism	5–10% of all hypertensives; ~20% of resistant HTN
Renovascular disease (RAS)	1–5%
Pheochromocytoma/Paraganglioma	Rare; 2–8 per million/year
Coarctation of the aorta	Uncommon in adults
Cushing syndrome	Uncommon
Thyroid disorders (hypo/hyperthyroidism)	Uncommon

Drug/substance causes include:

NSAIDs, oral contraceptives, systemic corticosteroids
Amphetamines, cocaine, MDMA, cannabis
Angiogenesis inhibitors (bevacizumab, sunitinib, sorafenib)
Cyclosporine, tacrolimus, erythropoietin
MAOIs, decongestants, antipsychotics
Herbal agents: ephedra (Ma-Huang), licorice, ginseng, guarana, arnica, St. John's wort

— NKF Primer on Kidney Diseases 8e, p. 698; Harrison's 22E, p. 2181

Pathophysiology by Cause

1. Obstructive Sleep Apnea

Repeated episodes of upper-airway obstruction cause intermittent hypoxia → sympathetic nervous system activation → increased peripheral vascular resistance and BP. Abnormalities of the RAAS and fluid redistribution also contribute. BP elevation correlates directly with OSA severity.

2. Renal Parenchymal Disease (CKD)

Any CKD etiology can cause hypertension. ~75% of patients with GFR <45 mL/min are hypertensive. Mechanisms:

Sodium and water retention (reduced GFR)
RAAS activation (renal ischemia signals)
Proteinuria independently increases sodium retention and BP

Glomerular diseases tend to produce hypertension at higher GFRs than interstitial diseases.

3. Renovascular Hypertension (Renal Artery Stenosis)

Two main types:

Atherosclerotic RAS (ARAS): >90% of cases. Unilateral lesions near the origin of the renal artery. Older patients with widespread ASCVD.
Fibromuscular Dysplasia (FMD): <10% of cases. Younger women. Distal artery involvement with classic "string of beads" angiographic appearance.

Mechanism: Renal ischemia → renin release → angiotensin II–mediated vasoconstriction and aldosterone secretion → hypertension and sodium retention. In unilateral disease, the contralateral kidney compensates with pressure natriuresis. In bilateral disease, sodium retention dominates and renin may be paradoxically normal/low. A stenosis typically requires >70% luminal narrowing to become hemodynamically significant.

4. Primary Aldosteronism

Caused by bilateral adrenal hyperplasia (~60%) or unilateral aldosterone-producing adenoma (~40%). Somatic mutations in KCNJ5 (inwardly rectifying K⁺ channel) allow Na⁺ influx → chronic membrane depolarization → Ca²⁺ influx → aldosterone hypersecretion.

Aldosterone excess → renal Na⁺ retention → volume expansion → BP elevation + suppressed renin + hypokalemia (via K⁺ excretion).

5. Pheochromocytoma / Paraganglioma (PPGL)

Tumors of adrenomedullary chromaffin cells (pheo) or extraadrenal sympathetic ganglia (paraganglioma) secrete epinephrine, norepinephrine, or dopamine → severe hypertension via α₁-receptor–mediated vasoconstriction. Episodic catecholamine release causes paroxysmal hypertension.

6. Coarctation of the Aorta

Constriction of the descending thoracic aorta (usually distal to the left subclavian artery) → mechanical obstruction → increased BP in upper extremities + reduced perfusion to kidneys → RAAS activation → further BP elevation.

7. Cushing Syndrome

Glucocorticoid excess → sodium retention (through mineralocorticoid receptor activation), increased angiotensinogen, potentiation of vasopressor responses.

8. Thyroid Disorders

Hypothyroidism: Increased peripheral vascular resistance (loss of thyroid-mediated vasodilation), decreased heart rate → diastolic hypertension predominant
Hyperthyroidism: Increased cardiac output, decreased peripheral vascular resistance → systolic hypertension predominant

— Harrison's 22E, pp. 2180–2183; NKF Primer 8e, pp. 700–706

Symptoms

Most patients with secondary hypertension are asymptomatic from hypertension itself. Symptoms are often clues to the underlying cause:

Cause	Symptoms/Signs
OSA	Snoring, daytime sleepiness, nocturnal gasping/choking, obesity, crowded oropharynx
Renovascular (FMD)	Young woman, abrupt-onset or resistant hypertension, abdominal bruit
Renovascular (ARAS)	Older patient, diffuse atherosclerosis, abdominal bruit, flash pulmonary edema
Primary aldosteronism	Muscle weakness, cramps, polyuria/nocturia (from hypokalemia), atrial fibrillation
Pheochromocytoma	Classic triad: episodic headache, palpitations, diaphoresis; pallor, paroxysmal BP spikes
Cushing syndrome	Weight gain (central obesity), moon face, buffalo hump, striae, glucose intolerance
Hypothyroidism	Fatigue, cold intolerance, constipation, bradycardia, dry skin
Hyperthyroidism	Heat intolerance, weight loss, palpitations, tremor, tachycardia
Coarctation of aorta	BP discrepancy arms > legs, weak femoral pulses, young patient, bicuspid aortic valve
CKD	Fatigue, hematuria, proteinuria (foamy urine), edema, elevated creatinine

Diagnosis

Initial Evaluation (All Suspected Secondary HTN)

Serum electrolytes, creatinine, eGFR, urinalysis with microscopy and protein-to-creatinine ratio
Fasting glucose, lipid panel
ECG, echocardiogram for LVH
Thyroid function tests (TSH)

Specific Screening Tests by Cause

Cause	Screening Test	Confirmatory Test
OSA	Epworth Sleepiness Scale, overnight oximetry	Polysomnography (gold standard)
Renal parenchymal disease	Urinalysis, creatinine, eGFR	Renal ultrasound, CT, renal biopsy (if glomerulonephritis suspected)
Renovascular (RAS)	Renal duplex ultrasound	CTA or MRA (preferred non-invasive); renal angiography (gold standard)
Primary aldosteronism	Plasma aldosterone/renin ratio (high ratio + high aldosterone)	Saline suppression test, captopril challenge; adrenal vein sampling (gold standard for lateralization)
Pheochromocytoma	24-h urinary fractionated metanephrines or plasma free metanephrines	MIBG scintigraphy; CT/MRI of adrenals
Cushing syndrome	24-h urinary free cortisol or late-night salivary cortisol	Low-dose dexamethasone suppression test; 24-h UFC
Coarctation of aorta	BP in arms vs. legs (gradient >20 mmHg), chest X-ray (rib notching)	CT or MR angiography; echocardiography
Thyroid disorder	TSH, free T4	—

— NKF Primer 8e, pp. 700–716; Harrison's 22E, pp. 2179–2183

Differential Diagnosis

Secondary hypertension must be distinguished from primary (essential) hypertension and from each other:

Primary HTN: No identifiable cause; gradual onset; family history; responds to standard therapy; no biochemical red flags
White-coat hypertension: Elevated office BP, normal ambulatory monitoring
Pseudohypertension: False elevation due to stiff arteries (elderly); confirmed by intra-arterial measurement
Pseudopheochromocytoma: Labile/paroxysmal HTN without biochemical evidence of catecholamine excess; includes panic disorder, sympathomimetic drug use, alcohol withdrawal, hyperthyroidism, baroreflex failure, carcinoid syndrome
Neurogenic HTN: Raised intracranial pressure (Cushing reflex), brain tumors

Treatment

Treatment is directed at the underlying cause whenever possible, with antihypertensive drug therapy as adjunct or primary management when the cause cannot be cured.

1. Obstructive Sleep Apnea

CPAP (continuous positive airway pressure): first-line; BP reduction is modest (~3/2 mmHg on average but greater with resistant HTN, AHI >30, and good adherence ≥4 h/night)
Lifestyle: weight loss (most effective), alcohol avoidance, sleep-position modification
Antihypertensive agents: beta-blockers (evidence suggests particular efficacy), spironolactone (targets volume/aldosterone component)

2. Renal Parenchymal Disease (CKD)

ACE inhibitors or ARBs: first-line (reduce proteinuria and slow CKD progression)
Diuretics: Thiazide/thiazide-like (chlorthalidone 12.5–25 mg/day effective even in advanced CKD); loop diuretics for GFR <30 mL/min
SGLT2 inhibitors (e.g., empagliflozin, dapagliflozin): reduce BP, proteinuria, and CKD progression
Finerenone (nonsteroidal MRA): additional BP reduction in advanced CKD
Target BP: <130/80 mmHg; often requires ≥3 agents

3. Renovascular Hypertension

Fibromuscular Dysplasia:

Percutaneous transluminal angioplasty (PTA): first-line, preferred; achieves cure in 26–54% depending on FMD subtype; stenting rarely needed
If surgery required: surgical reconstruction for complex lesions
Medical therapy (if PTA declined): ACE inhibitor or ARB + low-dose aspirin
Screen for extrarenal FMD: one-time head-to-pelvis CT/MR angiography

Atherosclerotic RAS:

Medical therapy preferred (RCTs show no benefit of PTA over medical therapy for BP or renal preservation)
ACE inhibitor or ARB (caution with bilateral RAS or solitary kidney — monitor creatinine/K⁺)
Statins, antiplatelet therapy, and risk-factor control (same as other ASCVD)
PTA considered only for recurrent flash pulmonary edema or progressive renal failure

4. Primary Aldosteronism

Unilateral adenoma:

Laparoscopic unilateral adrenalectomy (procedure of choice)
Preoperative preparation: spironolactone to normalize K⁺ and BP
Cure of hypertension more likely if: age <50, BMI <26, duration <5 years, ≤2 antihypertensives, normal renal function

Bilateral hyperplasia (or surgery declined):

Spironolactone 25–150 mg/day (start 25 mg/day, titrate) — first-line MRA
Eplerenone (if spironolactone intolerated) — use 2:1 dose ratio with twice-daily dosing
Amiloride — useful alternative if MRAs not tolerated
Thiazide diuretics as add-on (monitor K⁺ carefully)
Calcium channel blockers also effective for BP control

5. Pheochromocytoma / Paraganglioma

Surgical resection (laparoscopic adrenalectomy): definitive treatment
Preoperative preparation (essential — minimum 10–14 days):
- Alpha-blockade first: phenoxybenzamine (non-selective, irreversible) 10 mg BID, titrate to 20–40 mg BID; or doxazosin 2–16 mg/day; or prazosin 1–5 mg TID
- Beta-blockade second (only AFTER alpha-blockade to avoid hypertensive crisis from unopposed alpha stimulation): propranolol 20–40 mg TID or metoprolol 25–50 mg BID
- High-sodium diet + adequate hydration (prevent post-op hypotension)
For inoperable/malignant disease: metyrosine (tyrosine hydroxylase inhibitor), chemotherapy (cyclophosphamide/vincristine/dacarbazine), MIBG therapy

6. Coarctation of the Aorta

Percutaneous balloon angioplasty ± stenting: preferred in adults for localized CoA
Surgery: reserved for complex lesions not amenable to percutaneous approach
Proceed when translesional gradient >20 mmHg on angiography
Antihypertensive therapy pre/post-procedure: ACE inhibitors, ARBs, beta-blockers

7. Cushing Syndrome

Surgical resection of causative lesion (pituitary adenoma via transsphenoidal surgery for Cushing disease; adrenalectomy for adrenal adenoma; removal of ectopic ACTH source)
Medical: ketoconazole 400–1200 mg/day, metyrapone 500–3000 mg/day, pasireotide (for Cushing disease), or mifepristone (for glucose intolerance/DM)
Antihypertensives as adjunct

8. Thyroid Disorders

Hypothyroidism: levothyroxine replacement (1.6 mcg/kg/day, titrate to normal TSH) — BP usually normalizes
Hyperthyroidism: thionamides (methimazole 5–30 mg/day or propylthiouracil 50–150 mg TID), radioactive iodine, or surgery; beta-blockers (propranolol 40–160 mg/day) for symptomatic control

9. Drug-Induced Hypertension

Identify and discontinue or substitute the offending agent
If continuation required (e.g., anti-VEGF therapy for cancer): add antihypertensive therapy; treatment continues unless BP is uncontrollable or severe renal injury develops

Sources:

Harrison's Principles of Internal Medicine 22E (2025), pp. 2179–2183
NKF Primer on Kidney Diseases 8e, pp. 698–716

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