Secondary Hypertension Has a Treatable Underlying Cause. Here Is When to Look for One.

The Scene

The patient in this scene is a composite. Names, ages, and circumstances are changed to protect privacy.

Marcus is 34 years old and he has been on three blood pressure medications for eighteen months. His cardiologist in Springfield started him on lisinopril after a reading of 158/96 at a sports physical. The lisinopril brought it down to 142/90. They added amlodipine. Now it is 138/88. His cardiologist is preparing to add a third agent.

During the medication review, Marcus mentions something almost as an aside: he has been tired for about six months, he has had some muscle weakness in his legs, and he went to the bathroom seven times last night.

His cardiologist orders a basic metabolic panel. The potassium comes back at 2.8 mEq/L.

Low potassium. Difficult-to-control blood pressure in a young man. Muscle weakness. Polyuria.

His cardiologist does not add the third blood pressure medication that day. Instead, she orders an aldosterone-to-renin ratio.

The result: aldosterone 42 ng/dL, renin 0.4 ng/mL/hr. Aldosterone-to-renin ratio: 105. The normal upper limit is approximately 30.

Marcus does not have essential hypertension. He has primary aldosteronism. The aldosterone-producing tumor in his left adrenal gland has been quietly raising his blood pressure for at least two years. After laparoscopic left adrenalectomy, his blood pressure normalizes. He stops all three medications.

What It Is

The Plain-Language Definition

Secondary hypertension is raised blood pressure caused by a specific, identifiable medical condition. Unlike essential hypertension, which arises from a complex interplay of genetic and environmental factors without a single cause, secondary hypertension has a traceable origin. Find the origin, treat it effectively, and in many cases the blood pressure normalizes or becomes far easier to control.

Secondary hypertension accounts for approximately 5-10% of all hypertension cases. In the general hypertensive population, that fraction seems small. But given that approximately 116 million Americans have hypertension, 5-10% represents 5.8 to 11.6 million people with a potentially correctable cause that may never be investigated.

The stakes of missing secondary hypertension are not trivial. A patient with primary aldosteronism carries cardiovascular risk that exceeds their blood pressure level alone because aldosterone has independent toxic effects on the heart and vasculature beyond what raised pressure alone would cause 5 / Solid . A patient with pheochromocytoma faces intermittent hypertensive crises that can precipitate stroke, MI, or sudden death. A patient with renovascular hypertension may progress to ischemic nephropathy if the renal artery stenosis is not addressed.

The case for investigation is straightforward: secondary hypertension should be excluded in every patient whose clinical picture is inconsistent with simple essential hypertension.

When to Look for a Secondary Cause

Several clinical features should prompt a formal evaluation for secondary causes of hypertension:

1. Onset before age 30 (essential hypertension rarely presents young unless there is obesity or strong family history)
2. Blood pressure that is unusually severe (Stage 2 at first presentation, especially in young patients)
3. Resistant hypertension: blood pressure above goal on three agents including a diuretic, with documented adherence
4. Sudden worsening of previously controlled hypertension
5. Hypokalemia unprovoked by diuretic therapy (the most important clue for primary aldosteronism)
6. Episodes of hypertension that are paroxysmal (episodic rather than sustained), particularly with headache, palpitations, and diaphoresis (the classic triad for pheochromocytoma)
7. Hypertension in the setting of snoring, witnessed apneas, or excessive daytime sleepiness (obstructive sleep apnea)
8. Hypertension that is poorly controlled despite multiple agents in a patient with a renal bruit, abdominal bruit, or rising creatinine after starting an ACE inhibitor or ARB
9. Cushingoid features: central obesity, purple striae, dorsal fat pad, moon facies, proximal muscle weakness

The Mechanism

Primary Aldosteronism: The Most Common and Most Missed Secondary Cause

Primary aldosteronism (PA) is the most prevalent secondary cause of hypertension. For decades, it was thought to account for 1-2% of hypertension cases and was considered a zebra diagnosis. The assumption was wrong.

When systematic screening with the aldosterone-to-renin ratio (ARR) is applied to unselected hypertensive populations, PA prevalence ranges from 5-13% 5 / Solid . Among patients with resistant hypertension, prevalence approaches 20% 5 / Solid . It is not a zebra. It is a horse that most clinicians are taught to call a zebra.

The mechanism: adrenal tissue (either a unilateral adenoma or bilateral adrenal hyperplasia) autonomously secretes excess aldosterone independent of renin and angiotensin II control. Excess aldosterone tells the kidneys to retain sodium and excrete potassium. The sodium retention expands plasma volume, raises blood pressure, and suppresses renin through negative feedback. The potassium excretion produces hypokalemia. The autonomous aldosterone secretion continues regardless.

The classic teaching was that hypokalemia is required to suspect PA. The PATHWAY-2 trial 5 / Solid 00257-3) and the PA-Genetics Consortium data have overturned this: most patients with PA have normal potassium. Normokalemic PA is far more common than hypokalemic PA.

The aldosterone-to-renin ratio screening test is drawn as a morning, ambulatory, non-fasting sample. Many antihypertensive medications affect aldosterone and renin levels, but most current guidelines recommend screening without stopping medications (adjusting interpretation accordingly) rather than the logistical nightmare of a four-week medication washout 5 / Solid .

When the ARR is raised (typically above 30 using aldosterone in ng/dL and renin in ng/mL/hr), confirmatory testing is performed: either a saline suppression test (failure to suppress aldosterone after 2 liters of IV saline) or an oral sodium loading test. Once confirmed, adrenal CT imaging is obtained to distinguish adenoma from bilateral hyperplasia. Adrenal venous sampling (AVS) is the gold standard for lateralization when surgery is considered, because CT misclassifies unilateral vs bilateral disease in approximately 20-25% of cases 5 / Solid .

Unilateral adenoma: laparoscopic adrenalectomy. Bilateral hyperplasia: mineralocorticoid receptor antagonist (spironolactone or eplerenone).

Renal Artery Stenosis: Renovascular Hypertension

The kidney responds to reduced blood flow by activating RAAS. When stenosis narrows a renal artery, the ischemic kidney perceives reduced perfusion as systemic hypoperfusion, even if total blood pressure is raised. It releases renin. Renin generates angiotensin II. Angiotensin II raises blood pressure. The blood pressure elevation is a compensatory response to perceived underperfusion of one kidney.

Atherosclerotic renal artery stenosis (ARAS) is the more common form, occurring in the same patients who have coronary and peripheral arterial disease. It typically affects the ostium or proximal portion of the renal artery. Fibromuscular dysplasia (FMD) is the other major cause, predominantly affecting young women, and typically involves the mid-to-distal renal artery in a “string of beads” pattern on imaging.

The clinical clues: new or worsening hypertension with rising creatinine after starting an ACE inhibitor or ARB (the ACE inhibitor blocks the angiotensin II-mediated efferent arteriolar constriction that had been maintaining GFR in the stenotic kidney), an abdominal bruit, asymmetric kidneys on imaging, or flash pulmonary edema in a patient with bilateral renal artery stenosis.

The treatment question for ARAS has been clarified by the CORAL trial: stent revascularization of atherosclerotic renal artery stenosis does not improve blood pressure or renal outcomes compared to target medical therapy 5 / Solid . For FMD, balloon angioplasty (without stenting) is effective and is recommended for hemodynamically significant lesions.

Pheochromocytoma and Paraganglioma

Pheochromocytomas (adrenal tumors) and paragangliomas (extra-adrenal chromaffin cell tumors) secrete catecholamines (epinephrine, norepinephrine, and occasionally dopamine) either continuously or in bursts. The resulting hypertension can be sustained or paroxysmal.

The classic triad of episodic hypertension, headache, palpitations, and diaphoresis is present in fewer than half of patients. Many patients present with sustained hypertension and have no dramatic episodes. Some are detected incidentally when adrenal imaging is performed for another reason (an adrenal incidentaloma).

The cardiovascular consequences of undiagnosed pheochromocytoma are serious. Catecholamine excess can produce hypertensive crisis, pulmonary edema, hypertensive encephalopathy, catecholamine cardiomyopathy (a form of stress cardiomyopathy), and sudden death. In the perioperative setting, undiagnosed pheochromocytoma is a source of intraoperative hypertensive crisis.

Screening is biochemical: 24-hour urinary fractionated metanephrines and catecholamines, or plasma fractionated metanephrines. Plasma metanephrines have high sensitivity (96-99%) at the cost of false positives 5 / Solid . Imaging with CT or MRI locates the tumor. Functional imaging with MIBG scintigraphy or PET (using 68-Gallium DOTATATE) is used for multifocal or metastatic disease.

Treatment: alpha-blockade with phenoxybenzamine or doxazosin first (always before beta-blockade, to prevent paradoxical hypertensive crisis from unopposed alpha stimulation), then beta-blockade to control reflex tachycardia, followed by surgical resection.

Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is the most common identifiable contributor to resistant hypertension. Estimates suggest that 30-40% of hypertensive patients have OSA 5 / Solid 17450-6), and the relationship is bidirectional: OSA raises blood pressure through nocturnal sympathetic activation and hypoxia-driven vasopressor responses, and obesity drives both conditions simultaneously.

The blood pressure effects of OSA are concentrated in the nighttime. Non-dipping and reverse-dipping on ambulatory blood pressure monitoring (blood pressure that fails to fall at night or actually rises) should prompt evaluation for OSA. The history from a bed partner (witnessed apneas, loud snoring, gasping) is the most sensitive initial screening tool, more informative than any questionnaire.

CPAP reduces blood pressure by approximately 2-3 mmHg systolic in hypertensive OSA patients, a modest but real effect 5 / Solid . The effect is larger in patients with more severe OSA and those with more severe hypertension. CPAP does not cure hypertension in most patients, but it makes it easier to control.

Cushing Syndrome: Cortisol Excess

Cortisol excess from any cause (Cushing disease from a pituitary ACTH-producing adenoma, adrenal cortisol-producing adenoma, or exogenous glucocorticoid administration) raises blood pressure through multiple mechanisms: cortisol occupies mineralocorticoid receptors and mimics aldosterone’s sodium-retaining effects, cortisol increases hepatic angiotensinogen production, and cortisol has direct vasopressor effects.

The clinical features of Cushing syndrome are well known (central obesity, buffalo hump, purple striae, moon facies, proximal muscle weakness, easy bruising, glucose intolerance) but are often present in incomplete form. Screening tests: 24-hour urinary free cortisol, late-night salivary cortisol (the most sensitive single test), or overnight 1 mg dexamethasone suppression test 5 / Solid .

Thyroid Disease

Both hypothyroidism and hyperthyroidism affect blood pressure by different mechanisms.

Hypothyroidism: reduced cardiac output, increased systemic vascular resistance, raised diastolic blood pressure. Thyroid hormone replacement normalizes cardiovascular parameters.

Hyperthyroidism: increased heart rate, increased cardiac output, raised systolic blood pressure with low or normal diastolic (wide pulse pressure). Beta-blockers provide rapid symptomatic control while definitive therapy (radioactive iodine, antithyroid drugs, or surgery) normalizes thyroid function.

Thyroid function testing (TSH) is standard in the initial evaluation of new hypertension.

How We Diagnose It

The Screening Algorithm

The workup for secondary hypertension is not performed on every hypertensive patient. It is triggered by clinical features. The basic evaluation at initial hypertension diagnosis (metabolic panel, urinalysis, TSH, lipid panel, ECG) screens passively for thyroid disease, CKD, and metabolic abnormalities.

When the clinical trigger criteria listed in Section 2 are present, targeted workup is added:

For primary aldosteronism: Aldosterone-to-renin ratio. If screening-positive, confirmatory testing (salt loading test or fludrocortisone suppression test). If confirmed, CT adrenal. If CT suggests unilateral adenoma and patient is a surgical candidate, adrenal venous sampling before surgery.

For renal artery stenosis: Renal artery duplex ultrasound (non-invasive, no contrast, good sensitivity for ostial lesions). CT angiography or MR angiography for confirmation. ACE inhibitor renography (captopril scintigraphy) has largely been replaced by cross-sectional imaging.

For pheochromocytoma: Plasma fractionated metanephrines (preferred) or 24-hour urine fractionated metanephrines. If positive, cross-sectional imaging (CT abdomen/pelvis). If CT negative or multifocal disease, functional imaging.

For Cushing: Late-night salivary cortisol (most sensitive, easiest for outpatient), 24-hour urine free cortisol (confirms diagnosis), overnight dexamethasone suppression test.

For OSA: Sleep questionnaire (Epworth Sleepiness Scale, STOP-BANG). Polysomnography (in-lab or home-based) when clinical suspicion is present.

The Cost of Screening

One concern raised about systematic aldosteronism screening is resource utilization. The ARR is a blood test and costs less than $50. A saline suppression test (if needed for confirmation) costs a few hundred dollars and one morning in a hospital infusion suite. An adrenal CT scan costs a few hundred to a thousand dollars depending on the setting. Against this, consider the cost of three antihypertensive medications for life, the cost of end-organ damage from uncontrolled hypertension, and the independent cardiovascular toxicity of excess aldosterone. The economic case for screening is strong 5 / Solid .

The Evidence

PATHWAY-2: Spironolactone in Secondary Hypertension Context

The PATHWAY-2 trial, the same trial that shaped the treatment of resistant hypertension (discussed in PRES-003), provides important insights into the prevalence of unsuspected primary aldosteronism in what had been labeled “resistant hypertension.” In PATHWAY-2, patients randomized to spironolactone (a mineralocorticoid receptor antagonist) had dramatically better blood pressure control than those randomized to bisoprolol or doxazosin 5 / Solid 00257-3). The magnitude of response to aldosterone blockade supports the inference that excess aldosterone activity, even without meeting formal criteria for primary aldosteronism, is a prevalent driver of resistant hypertension.

The CORAL Trial: Settling the Renal Artery Stenting Question

The 2014 CORAL trial randomized 947 patients with atherosclerotic renal artery stenosis (≥80% stenosis, or 60-80% stenosis with a pressure gradient) to stenting plus target medical therapy versus target medical therapy alone 5 / Solid . At 43 months, there was no difference in the primary endpoint (cardiovascular or renal events) or in blood pressure. Renal stenting for atherosclerotic disease is not supported by evidence. This is a specific and important finding that has changed practice; many patients who would previously have undergone renal artery stenting now receive medical management.

Sex Differences in Secondary Hypertension

Fibromuscular dysplasia affects women far more than men, with a female-to-male ratio of approximately 9:1 5 / Solid . This is the renal artery disease of young women, and it is distinct from atherosclerotic renal artery stenosis both mechanistically and therapeutically (angioplasty, not stenting; not driven by lipid management).

Primary aldosteronism presents similarly in men and women, but the surgical cure rates are higher in women for unknown reasons 5 / Solid .

The Patient Experience

The Relief of a Diagnosis

Patients who are found to have a secondary cause of hypertension after years of multi-drug therapy frequently report the discovery as one of the most significant medical events of their lives. Not because the diagnosis is simple, but because it changes the narrative from “you have a condition you will manage forever” to “you have a condition with a specific cause that we can address.” This is not a trivial difference in patient experience.

Marcus, the composite patient in this article’s opening scene, described his post-adrenalectomy experience in these terms: “I had spent two years thinking I just had bad blood pressure genes. Turns out I had a tumor.”

The relief is real and the clinical implication is clear: secondary causes should be excluded before a patient is labeled with lifelong essential hypertension, particularly when the clinical picture is inconsistent.

What Investigation Looks Like

The workup for secondary hypertension is usually not dramatic. For most patients, it begins with a blood draw (aldosterone, renin, potassium if not already done, metanephrines if paroxysmal symptoms are present) and an office visit to review results. CT imaging is added when biochemical screening is positive. For OSA evaluation, a home sleep study can be ordered through primary care in most systems without requiring a sleep specialist referral.

The experience of adrenal venous sampling, however, is an exception. AVS is an interventional procedure requiring fluoroscopy, cannulation of both adrenal veins, and simultaneous hormone measurement. It is not painful but requires an interventional radiology or cardiology team experienced in the technique. Experienced centers (in Chicago, Northwestern Medicine and University of Chicago; in central Illinois, referral to UIUC-affiliated programs or Indianapolis) achieve bilateral AVS cannulation rates above 90%; inexperienced centers may have failure rates of 30-50%, making the procedure useless 5 / Solid .

Decisions and Trade-Offs

When to Screen Broadly vs. When to Wait

The tension in secondary hypertension evaluation is between the cost and complexity of systematic screening and the risk of missing treatable causes. Current guidelines (Endocrine Society, European Society of Hypertension) recommend screening for primary aldosteronism in patients with:

• Hypertension with spontaneous or diuretic-induced hypokalemia
• Resistant hypertension
• Blood pressure above 150/100 on three agents
• Hypertension with adrenal incidentaloma
• Hypertension with a family history of early-onset hypertension or stroke under age 40
• Hypertension in first-degree relatives with primary aldosteronism

The case for broader screening (all hypertensive patients) remains debated. The ARR is cheap enough that broader application would be feasible; the bottleneck is confirmatory testing and AVS, which require specialized resources.

For pheochromocytoma, screening is reserved for patients with episodic symptoms, an adrenal incidentaloma, familial syndromes (MEN2, von Hippel-Lindau, neurofibromatosis), or difficult-to-control hypertension. Universal screening is not supported.

The Medication Management Question

When a secondary cause is suspected but not yet confirmed, should medications be changed? Generally, blood pressure must be controlled in the interim. But some medications complicate the workup:

• Spironolactone and eplerenone falsely suppress the ARR (by raising renin) and should be stopped for at least 4 weeks before PA screening when possible
• Beta-blockers can suppress plasma renin and falsely increase the ARR; they should ideally be avoided in the pre-screening period
• ACE inhibitors and ARBs may trigger acute renal deterioration in bilateral renal artery stenosis

These considerations do not mandate stopping all blood pressure medications before screening. They require thoughtful choice of agents and interpretation of results in context. An internist or cardiologist comfortable with the nuances can manage this without specialized endocrinology referral in most cases.

Clinical Synthesis

The Investigative Principle

The core clinical thesis is that most cardiovascular events are not random misfortune but are predictable consequences of identifiable and addressable conditions. Secondary hypertension is a powerful illustration.

When a 34-year-old man is found to have primary aldosteronism after two years of inadequately controlled hypertension on three drugs, the question is not only “how do we treat this now?” The question is also “how long has this been present, what organ damage has already accumulated, and how much of that damage was preventable?”

Aldosterone has independent effects on the cardiovascular system beyond blood pressure elevation. It promotes myocardial fibrosis, vascular inflammation, and left ventricular hypertrophy. A patient with an aldosteronoma who is treated with three antihypertensive drugs that modestly lower blood pressure but do not address the aldosterone excess is accumulating cardiovascular damage at a rate that blood pressure reduction alone cannot arrest 5 / Solid .

This is a preventable situation. The ARR test that would have identified it costs approximately $30 to $50.

A structured cardiovascular assessment specifically includes an evaluation for secondary hypertension in any patient who presents with:

• Hypertension diagnosed before age 40
• Hypertension requiring more than two medications
• Hypertension with unexplained hypokalemia
• Hypertension with paroxysmal symptoms

For clinicians at Carle Foundation Hospital in Urbana, the endocrinology and nephrology programs are co-located with cardiology, enabling rapid specialist referral when secondary causes are identified. For patients in more rural settings (Mattoon, Paris, Danville), telemedicine evaluation with the Carle secondary hypertension program is available before committing to in-person workup.

The principle is not to chase rare diagnoses in every hypertensive patient. The principle is to not assume essential hypertension when the clinical picture is inconsistent with it. The 34-year-old man with difficult-to-control blood pressure and a potassium of 2.8 is not a difficult case if the right question is asked.

Extended Evidence Review: Diagnosis and Management of Secondary Hypertension Causes

Primary Aldosteronism: A Deeper Look

Primary aldosteronism is the most common secondary cause of hypertension, affecting 5-10% of all hypertensive patients and approximately 20% of patients with resistant hypertension. It is dramatically underdiagnosed: most patients with primary aldosteronism do not have the classic features (unprovoked hypokalemia, severe hypertension) and present instead with moderate to severe hypertension that is simply poorly controlled on standard therapy.

The PAPY Study (Prevalence of Primary Aldosteronism in Patients with Arterial Hypertension in Italy) screened 1,125 consecutive newly diagnosed hypertensive patients with aldosterone-to-renin ratio (ARR) and confirmatory testing. Primary aldosteronism was confirmed in 11.2% of the total cohort: substantially higher than the historically estimated 1-2% prevalence. 5 / Solid

Organ damage beyond blood pressure: Milliez and colleagues compared 124 primary aldosteronism patients to 465 essential hypertension patients matched for blood pressure, age, and sex. The primary aldosteronism patients had significantly higher rates of atrial fibrillation (12.1% vs 2.8%), stroke (12.9% vs 3.4%), and non-fatal MI (4.0% vs 0.6%), indicating that aldosterone exerts direct cardiovascular toxicity independent of its blood pressure effects. 5 / Solid This finding justifies aggressive diagnosis and treatment of primary aldosteronism even in patients whose blood pressure appears controlled.

Adrenal vein sampling (AVS) vs CT: CT scan classifies lateralization correctly in approximately 50-60% of primary aldosteronism cases; adrenal vein sampling is required for accurate lateralization before adrenalectomy is recommended. A young patient (below 35) with unilateral adenoma on CT can proceed to surgery without AVS per some guidelines, but the consensus for most patients is AVS first. 5 / Solid

Obstructive Sleep Apnea: Causality Established

The relationship between obstructive sleep apnea (OSA) and hypertension is bidirectional and causal. The Wisconsin Sleep Cohort Study followed 709 adults for 4 years and found that the odds ratio for developing hypertension was 3-fold higher in patients with severe OSA compared to no OSA, even after adjustment for obesity, age, and sex. 5 / Solid

Mechanisms:

1. Apnea episodes produce hypoxia and hypercapnia, activating the carotid body chemoreflex and triggering surges in sympathetic nervous system activity
2. Recurrent sympathetic surges during sleep cause endothelial dysfunction, arterial stiffening, and eventually sustained daytime hypertension
3. Negative intrathoracic pressure during obstructed breathing creates extreme cardiac afterload, stressing the left ventricle and promoting left ventricular hypertrophy
4. Intermittent hypoxia stimulates renal renin release, activating RAAS and contributing to sodium retention

Treatment effects on blood pressure: CPAP therapy reduces 24-hour ambulatory blood pressure by approximately 2-3 mmHg in OSA patients with hypertension: clinically meaningful when sustained over years but insufficient as sole antihypertensive therapy in severe hypertension. The HIPARCO trial (n=194, non-dipping hypertension and OSA) showed that CPAP reduced non-dipping in treated OSA, restoring the normal nocturnal BP dip in approximately 36% of patients, with associated reductions in major cardiovascular events in a smaller observational follow-up. 4 / Promising

The clinical implication: hypertension in an obese, snoring patient with daytime somnolence and non-dipping on ABPM should prompt formal sleep study. CPAP initiation may reduce antihypertensive medication requirements and provides cardiovascular benefits beyond the blood pressure effect (reduced atrial fibrillation burden, improved left ventricular function, reduction in arrhythmia).

Cushing Syndrome: The Under-Tested Cause

Cushing syndrome (excess cortisol from any source) affects approximately 1 in 500 patients with obesity and hypertension, making it less common than primary aldosteronism or OSA but more likely to be missed. Classical features (moon face, buffalo hump, purple striae, proximal myopathy, thin skin with easy bruising) are easily recognizable but often subtle or absent in early or mild hypercortisolism.

The overnight 1 mg dexamethasone suppression test is the standard screening test: normal suppression (cortisol below 1.8 mcg/dL the morning after 1 mg dexamethasone at 11 PM) effectively rules out Cushing syndrome. Failure to suppress warrants further evaluation with 24-hour urinary free cortisol and late-night salivary cortisol. 5 / Solid

Hypertension in Cushing syndrome is driven by multiple mechanisms: cortisol-mediated activation of mineralocorticoid receptors (cortisol at high concentrations binds the mineralocorticoid receptor, producing aldosterone-like sodium retention), cortisol-induced upregulation of angiotensin II receptors, and direct cortisol enhancement of pressor sensitivity. Treatment of the underlying cause (adrenalectomy for adrenal adenoma, transsphenoidal resection for pituitary ACTH-producing adenoma) can fully normalize blood pressure in many patients.

Extended Mechanism: Renovascular Hypertension in Practice

The Clinical Scenario for Renal Artery Stenosis Screening

Renovascular hypertension should be actively considered in specific clinical scenarios where the pre-test probability justifies further investigation:

1. Onset of severe hypertension before age 30 (especially in young women: fibromuscular dysplasia)
2. Accelerated or malignant hypertension newly developing in a patient with previously stable essential hypertension
3. Onset of stage 3 hypertension (systolic above 180 mmHg) in a patient above 55 with diffuse atherosclerosis
4. Unilateral small kidney on imaging not explained by other causes
5. Acute rise in creatinine (above 30%) after initiation of ACE inhibitor or ARB (bilateral RAS or RAS in a solitary kidney: a diagnostic clue)
6. Flash pulmonary edema in a patient with hypertension and atherosclerosis, without clear cardiac cause (“Pickering syndrome”: bilateral RAS causing acute cardiac decompensation)
7. Resistant hypertension despite maximally dosed three-drug therapy

Fibromuscular Dysplasia: The Young Woman’s Diagnosis

Fibromuscular dysplasia (FMD) is a non-inflammatory, non-atherosclerotic disease of the arterial wall that primarily affects medium-sized arteries, most commonly the renal arteries (60-75% of cases) and carotid/vertebral arteries. It produces a characteristic “string of beads” appearance on angiography from alternating areas of medial fibroplasia and webs.

FMD-associated renovascular hypertension typically presents in women between 15 and 50 years of age with severe, poorly controlled hypertension. The diagnosis is made with CT angiography or MR angiography of the renal arteries.

Treatment: balloon angioplasty (without stenting) is highly effective for hemodynamically significant renal FMD lesions, with technical success rates above 85% and cure or meaningful improvement of hypertension in 50-60% of patients. 5 / Solid This distinguishes FMD from atherosclerotic renal artery stenosis (where the CORAL trial showed no benefit from stenting).

The US Registry for Fibromuscular Dysplasia has documented over 2,000 patients and confirmed that FMD patients have higher rates of spontaneous coronary artery dissection (SCAD), intracranial aneurysms, and arterial dissections at other sites. A patient diagnosed with FMD in the renal arteries should have cervical and intracranial artery imaging to screen for concurrent FMD and aneurysm. 5 / Solid

Extended Patient Experience: The Workup That Changed Everything

When Secondary Hypertension Is Found

The discovery of a secondary cause of hypertension is often a turning point for patients who have struggled with poorly controlled blood pressure for years. A patient told for a decade that they simply have “hard to treat” essential hypertension who is then found to have a 2 cm adrenal adenoma on CT: the explanation for their persistent hypokalemia, resistant hypertension, and two prior hypertensive emergencies: experiences this as a diagnosis. Not a label, but an explanation.

The emotional and practical implications deserve attention:

• The potential for cure: Unilateral primary aldosteronism treated by adrenalectomy produces hypertension cure (defined as maintained BP below 140/90 without medications) in approximately 30-50% of patients and meaningful improvement in the remainder. This is the only cardiovascular disease where a surgical or procedural intervention can potentially eliminate the patient’s lifelong medication burden.
• Family implications: Some secondary causes (FMD, some endocrine tumors) have genetic components. A diagnosis of MEN2A (associated with pheochromocytoma) in one family member triggers cascade genetic testing in first-degree relatives.
• Cardiovascular risk recalibration: Primary aldosteronism patients, once diagnosed and treated, should have their cardiovascular risk reassessed: their cumulative aldosterone-mediated organ damage may have created a risk profile higher than their blood pressure numbers alone would suggest.

Illinois Referral Resources for Complex Secondary Hypertension

At Carle Foundation Hospital, suspected secondary hypertension beyond the initial ARR screening is managed through a collaborative approach between internal medicine, nephrology, endocrinology, and vascular surgery. Adrenal vein sampling is performed in the interventional radiology suite.

For fibromuscular dysplasia, the University of Illinois at Chicago has a dedicated FMD program. Northwestern Memorial Hospital in Chicago has both an endocrine hypertension program (for primary aldosteronism, pheochromocytoma, and Cushing) and a renal hypertension program with expertise in AVS.

Rural patients in central and southern Illinois accessing services through OSF Healthcare Saint Francis in Peoria can access endocrine hypertension evaluation and adrenal imaging. The OSF Multi-Specialty Group includes nephrology services with renovascular hypertension protocols.

Extended Mechanism: The Adrenal Axis and Hypertension

Pheochromocytoma: Diagnosis and Management in Detail

Pheochromocytoma accounts for approximately 0.1-0.5% of hypertension cases but is critical to identify because of its life-threatening catecholamine crisis potential. The clinical presentation varies from persistent severe hypertension to paroxysmal attacks of hypertension, tachycardia, sweating, and headache. The triad of headache, diaphoresis, and palpitations in a hypertensive patient should always prompt biochemical screening.

Biochemical diagnosis: The preferred initial test is plasma metanephrines (metanephrine and normetanephrine), which are continuous metabolites of catecholamines produced within the adrenal medulla. Sensitivity approaches 98% for adrenal pheochromocytoma. Urine fractionated metanephrines and catecholamines over 24 hours provide comparable sensitivity with slightly greater specificity. False positives occur with certain medications (tricyclic antidepressants, sympathomimetics, phenoxybenzamine) and can be reduced by testing after 30 minutes supine rest in a non-stressful environment.

Imaging: Once biochemically confirmed, CT of the abdomen and pelvis localizes the tumor in approximately 80-90% of cases. Functional imaging with DOTATATE PET-CT (which targets somatostatin receptors on neuroendocrine tumors) provides superior sensitivity for metastatic and extra-adrenal paraganglioma. MIBG scintigraphy is an older functional imaging modality still used at some centers.

Perioperative management: The most dangerous moment in pheochromocytoma management is surgical resection. Tumor manipulation during surgery produces massive catecholamine release. Pre-operative alpha-blockade for at least 10-14 days (phenoxybenzamine is the preferred irreversible alpha-blocker; doxazosin is an alternative) is mandatory. Beta-blockade is added only after adequate alpha-blockade is established: beta-blockade before alpha-blockade can produce paradoxical severe hypertension by eliminating beta-2-mediated vasodilation while leaving alpha-1 vasoconstriction unopposed. 5 / Solid

Genetic counseling is essential: approximately 30-40% of pheochromocytomas are associated with germline mutations in SDH genes (SDHB, SDHC, SDHD), VHL, RET (MEN2), NF1, or MAX. SDHB mutations are particularly associated with malignant pheochromocytoma and paraganglioma.

The Hypothyroidism Connection

Hypothyroidism produces diastolic hypertension through increased peripheral vascular resistance (thyroid hormone normally promotes vascular smooth muscle relaxation through direct genomic and non-genomic effects). Patients with untreated or undertreated hypothyroidism frequently have blood pressure that normalizes or improves substantially with thyroid hormone replacement: making TSH one of the most important and inexpensive secondary hypertension screening tests.

The bidirectional relationship is also present: hyperthyroidism produces systolic hypertension (raised cardiac output, increased stroke volume) and tachycardia. Both states normalize with appropriate treatment.

In clinical practice, TSH should be checked in any patient with new onset of hypertension, particularly if accompanied by fatigue, cold intolerance, weight gain, or constipation (hypothyroidism) or heat intolerance, weight loss, tremor, or diarrhea (hyperthyroidism). 5 / Solid

Extended Patient Experience: The Sequence of Testing

A systematic approach to secondary hypertension evaluation avoids both the cost of testing everyone with hypertension for rare causes and the harm of missing common causes in the patients most likely to have them. The principle: screen broadly in high-yield populations, confirm positive screens with specific tests.

Tier 1 screening (all resistant hypertension, all hypertension before age 40, all with hypokalemia or metabolic clues):

• Plasma aldosterone-to-renin ratio (primary aldosteronism)
• TSH (thyroid disease)
• Urinalysis with microscopy and serum creatinine (renal parenchymal disease, renal artery stenosis clue)
• Sleep study or polysomnography referral if OSA risk factors present

Tier 2 (if Tier 1 abnormal or clinical suspicion persists):

• Aldosterone: saline suppression test or oral sodium loading test for confirmatory PA testing
• Adrenal CT (PA) or renal artery duplex / CT angiography (RAS)
• Plasma or urine fractionated metanephrines (pheochromocytoma)
• 24-hour urine free cortisol or overnight dexamethasone suppression test (Cushing)

Tier 3 (specialist-driven, selective):

• Adrenal vein sampling for PA lateralization
• Dynamic MRI or functional CT for adrenal lesions
• DOTATATE PET for paraganglioma
• Genetic counseling and germline testing for hereditary syndromes

At Carle Foundation Hospital, the endocrine hypertension pathway uses this tiered approach. Most cases of secondary hypertension are identified in Tier 1. The specialist consultation resources in Tier 2 and 3 are concentrated at Carle’s Endocrinology Department and at Northwestern Medicine in Chicago for complex cases.

Extended Evidence Review: Adrenal Vein Sampling and Surgical Cure of Primary Aldosteronism

The Surgical Cure Problem

Primary aldosteronism is the most common surgically correctable cause of hypertension, yet fewer than 40% of patients with confirmed primary aldosteronism undergo adrenal vein sampling (AVS): the necessary test to determine whether the aldosterone excess is unilateral (surgically curable by adrenalectomy) or bilateral (requiring medical management with mineralocorticoid receptor antagonists).

The barriers to AVS are real: it requires experienced interventional radiologists, is technically demanding (cannulating the right adrenal vein is difficult and fails in up to 25% of attempts at high-volume centers, substantially higher at low-volume centers), and has limited availability outside academic medical centers.

The alternative to AVS: adrenal CT: misclassifies approximately 40% of cases. A unilateral adenoma on CT may be associated with bilateral hypersecretion on AVS; bilateral nodules on CT may turn out to have unilateral dominance. Using CT alone to make the surgical/medical decision results in unnecessary adrenalectomies (operating on the wrong adrenal) and missed surgical cures (not operating on unilateral cases misclassified as bilateral). 5 / Solid

The clinical principle: for any patient with confirmed primary aldosteronism who is a surgical candidate and willing to consider surgery, AVS is mandatory before proceeding to adrenalectomy. The referral to an experienced center (University of Illinois at Chicago, Northwestern, or Rush for Illinois patients) is appropriate even if it requires travel, because the consequences of surgical versus medical misclassification are significant.

Outcomes After Adrenalectomy for Primary Aldosteronism

When AVS correctly identifies unilateral aldosterone-producing adenoma and adrenalectomy is performed, outcomes are excellent. The PASO (Prospective Adrenalectomy Study for Primary Aldosteronism Outcomes) study found that:

• Complete clinical success (normotension without medications): approximately 37% at 6 months
• Partial clinical success (improved BP control on reduced medication): approximately 47%
• No improvement: approximately 16%

Clinical success is more likely in: younger patients (shorter duration of BP elevation, less arteriolar hypertension remodeling), patients without CKD, patients with fewer co-morbidities, and patients whose contralateral adrenal vein aldosterone suppression was confirmed on AVS. 5 / Solid 31799-5)

Extended Patient Experience: The Thyroid-Hypertension Connection

Hypothyroidism and Hypertension

Thyroid hormone is a major regulator of systemic vascular resistance. Hypothyroidism: with reduced T3/T4 production: produces raised peripheral vascular resistance (via reduced endothelial nitric oxide production and increased arterial stiffness), leading to diastolic hypertension. The pattern is typically raised diastolic pressure with near-normal systolic, producing a narrow pulse pressure: the hemodynamic signature of high peripheral resistance.

TSH screening for hypertension is inexpensive and clinically important. Overt hypothyroidism (TSH above 10 mIU/L with low free T4) is a treatable cause of hypertension. Subclinical hypothyroidism (TSH 4.5-10 mIU/L with normal free T4) has a more modest and inconsistent effect on blood pressure, but thyroid hormone replacement in patients with TSH above 7-10 mIU/L is associated with small but measurable reductions in systolic and diastolic BP in multiple meta-analyses.

For Marcus: the resistant hypertension patient whose secondary cause workup should include TSH: a TSH above 10 mIU/L would prompt thyroid hormone replacement before or concurrent with antihypertensive escalation.

Hyperthyroidism produces the opposite pattern: high systolic, wide pulse pressure, reflex tachycardia. Treating the hyperthyroidism substantially normalizes blood pressure. This is relevant in the patient with apparently new-onset systolic hypertension and weight loss, heat intolerance, or tremor: a clinical picture that should prompt TSH measurement before adding antihypertensives.

Illinois Secondary Hypertension Referral Resources

For Illinois patients who need secondary hypertension evaluation:

• Carle Foundation Hospital Hypertension Clinic (Urbana): Complete secondary hypertension workup for patients in central Illinois, including ARR, overnight dexamethasone suppression test, and OSA screening. Complex cases requiring AVS are referred to Chicago tertiary centers.
• University of Illinois at Chicago: Endocrinology and nephrology programs with adrenal venous sampling expertise for primary aldosteronism evaluation.
• Northwestern Medicine Feinberg School Hypertension Program: Complete secondary hypertension evaluation, renal artery imaging, FMD workup, and pheochromocytoma management.
• Rush University Medical Center: Nephrology hypertension program with renovascular expertise.

This program’s position on secondary hypertension: every patient labeled as having “resistant hypertension” who has not had a systematic secondary cause evaluation has an incomplete workup. Primary aldosteronism, OSA, renovascular disease, and hypothyroidism are each common enough and treatable enough that systematic screening changes clinical management in a clinically meaningful fraction of patients.

The Signal Check is fifteen questions mapping the cardiovascular risk pattern across the physiological domains most commonly missed in standard screenings. It produces a specific starting point for your next clinical conversation.