Adrenal Disorders: Cushing Syndrome, Addison Disease, and Pheochromocytoma

Adrenal disorders encompass a spectrum of conditions affecting the adrenal cortex and medulla, resulting in hormone excess or deficiency states. The three major adrenal disorders represent distinct pathophysiological mechanisms:

Cushing Syndrome is characterized by chronic exposure to excessive cortisol, either from endogenous overproduction or exogenous administration. [KEY_CONCEPT] The hypothalamic-pituitary-adrenal (HPA) axis normally maintains cortisol homeostasis through negative feedback, but this regulation is disrupted in Cushing syndrome.

Primary Adrenal Insufficiency (Addison Disease) results from destruction of the adrenal cortex, leading to deficiency of glucocorticoids, mineralocorticoids, and adrenal androgens. [HIGH_YIELD] Autoimmune adrenalitis accounts for 80-90% of cases in developed countries, while infectious causes (tuberculosis, histoplasmosis) predominate in developing regions.

Pheochromocytoma arises from chromaffin cells in the adrenal medulla (90%) or extra-adrenal paraganglia (10%), causing episodic or sustained catecholamine excess. [CLINICAL_PEARL] The "rule of 10s" historically described pheochromocytomas: 10% bilateral, 10% malignant, 10% extra-adrenal, and 10% hereditary, though genetic testing has revealed hereditary syndromes in up to 40% of cases.

Epidemiology:

• Cushing syndrome: 2-3 cases per million per year
• Addison disease: 4-6 cases per 100,000 population
• Pheochromocytoma: 0.1-0.6% of hypertensive patients

These conditions share common features of significant morbidity and mortality when undiagnosed, emphasizing the importance of early recognition and appropriate management.

The clinical manifestations of adrenal disorders reflect the specific hormonal imbalances involved:

Cushing Syndrome Clinical Features:

[HIGH_YIELD] Pathognomonic signs include wide purple striae, proximal muscle weakness, and easy bruising. Moon facies and buffalo hump are common but less specific.

Addison Disease Clinical Features:

• Primary symptoms: Fatigue, weakness, weight loss, anorexia
• Pathognomonic signs: Hyperpigmentation (especially buccal mucosa, palmar creases, surgical scars)
• Cardiovascular: Hypotension, orthostatic hypotension
• Gastrointestinal: Nausea, vomiting, abdominal pain, salt craving
• Electrolyte abnormalities: Hyponatremia, hyperkalemia, hypoglycemia

[CLINICAL_PEARL] Hyperpigmentation in Addison disease results from elevated ACTH cross-reacting with melanocortin receptors, distinguishing primary from secondary adrenal insufficiency.

Pheochromocytoma Clinical Features:

Classic Triad (occurs in <50% of patients):

1. Headache
2. Sweating
3. Palpitations/tachycardia

Additional manifestations:

• Hypertension (sustained in 50%, paroxysmal in 50%)
• Anxiety, tremor, pallor
• Chest or abdominal pain
• Weight loss
• Hyperglycemia

[HIGH_YIELD] **"4 H's" mnemonic: Headache, Heart palpitations, Hyperhydrosis (sweating), Hypertension. The absence of all four symptoms has high negative predictive value for excluding pheochromocytoma.

Cushing Syndrome Diagnostic Algorithm:

Clinical Suspicion ↓ Screening Tests (perform 2-3 tests): ├─ 24-hour urine free cortisol (>3x ULN) ├─ Late-night salivary cortisol (elevated) ├─ 1mg dexamethasone suppression test (cortisol >1.8 μg/dL) └─ Midnight serum cortisol (if hospitalized) ↓ If positive screening → Confirmatory testing ↓ Dexamethasone-CRH test or Midnight salivary cortisol × 2 ↓ Etiology determination: Plasma ACTH level ├─ Suppressed (<20 pg/mL) → Adrenal cause │ └─ Adrenal imaging (CT/MRI) └─ Elevated (>20 pg/mL) → Pituitary vs Ectopic └─ High-dose dexamethasone test └─ CRH stimulation test └─ Pituitary MRI

Addison Disease Diagnostic Criteria:

Primary Diagnostic Test:

• Morning cortisol <3 μg/dL strongly suggests adrenal insufficiency
• Morning cortisol >18 μg/dL excludes adrenal insufficiency
• Intermediate values (3-18 μg/dL) require ACTH stimulation test

ACTH Stimulation Test Protocol:

1. Baseline cortisol and ACTH levels
2. Administer 250 μg cosyntropin IV/IM
3. Measure cortisol at 30 and 60 minutes
4. Normal response: Cortisol >18-20 μg/dL at 30 or 60 minutes

[CLINICAL_PEARL] In acute illness, random cortisol <10 μg/dL suggests adrenal insufficiency, while >25 μg/dL indicates adequate adrenal reserve.

Additional Tests for Addison Disease:

• Elevated ACTH (>100 pg/mL) confirms primary adrenal insufficiency
• 21-hydroxylase antibodies (positive in 85% of autoimmune cases)
• Aldosterone and renin levels
• Adrenal imaging if infectious etiology suspected

Pheochromocytoma Diagnostic Approach:

Biochemical Testing (preferred initial tests):

• 24-hour urine: Catecholamines and metanephrines
• Plasma metanephrines: Most sensitive single test
• 24-hour urine metanephrines: Highest specificity

Diagnostic Thresholds:

• Plasma metanephrines >4× upper limit normal: 100% specificity
• Values 2-4× upper limit: Consider repeat testing or clonidine suppression

[HIGH_YIELD] Medications affecting catecholamine measurements:

• Increase: Tricyclic antidepressants, levodopa, methyldopa
• Decrease: Alpha-methyltyrosine

Imaging Studies:

• CT or MRI abdomen/pelvis after biochemical confirmation
• Functional imaging (MIBG, PET) for extra-adrenal or metastatic disease

Genetic Testing Indications:

• Age <45 years
• Bilateral/multifocal tumors
• Extra-adrenal paraganglioma
• Family history of pheochromocytoma/paraganglioma
• Associated clinical features (RET, VHL, NF1, SDH mutations)

Cushing Syndrome Management:

Surgical Management (first-line for most cases):

• Pituitary adenoma: Transsphenoidal surgery
• Adrenal adenoma: Unilateral adrenalectomy
• Adrenal carcinoma: En-bloc resection with lymphadenectomy
• Ectopic ACTH: Tumor resection when feasible

Medical Therapy Indications:

• Preoperative preparation
• Non-surgical candidates
• Persistent/recurrent disease
• Metastatic adrenal carcinoma

Medical Treatment Options:

Addison Disease Management:

Glucocorticoid Replacement:

• Hydrocortisone: 15-25mg daily (2/3 morning, 1/3 evening)
• Prednisolone: 3-5mg daily
• Dexamethasone: 0.25-0.75mg daily

[HIGH_YIELD] Stress dose steroids: 2-3× maintenance dose for minor stress, IV hydrocortisone 100mg q8h for major stress/surgery.

Mineralocorticoid Replacement:

• Fludrocortisone: 0.05-0.2mg daily
• Monitor electrolytes, blood pressure, and plasma renin activity

Patient Education Essentials:

• Medical alert bracelet/card
• Stress dose steroid protocol
• Injectable hydrocortisone for emergencies
• Sick day management guidelines

Pheochromocytoma Management:

Preoperative Preparation (essential):

α-blockade (start 7-14 days before surgery): Phenoxybenzamine 10mg BID → titrate to effect ↓ β-blockade (start only after α-blockade): Propranolol or metoprolol for tachycardia ↓ Fluid resuscitation: High-salt diet, adequate hydration ↓ Goal: Seated BP <130/80, standing BP >90 systolic

[CLINICAL_PEARL] Never start β-blockers before α-blockade - may precipitate hypertensive crisis due to unopposed α-stimulation.

Surgical Approach:

• Laparoscopic adrenalectomy: Standard for benign, unilateral tumors <6cm
• Open surgery: Large tumors, suspected malignancy, or anatomical constraints
• Intraoperative monitoring: Arterial line, central venous access
• Anesthetic considerations: Avoid drugs that stimulate catecholamine release

Medical Management (non-surgical candidates):

• α-blockers: Phenoxybenzamine, doxazosin
• Calcium channel blockers: Amlodipine, nicardipine
• α-methyltyrosine: Reduces catecholamine synthesis (specialty use)

Malignant Pheochromocytoma:

• Chemotherapy: Cyclophosphamide, vincristine, dacarbazine (CVD)
• Targeted therapy: Sunitinib for metastatic disease
• Radiotherapy: MIBG therapy with I-131 or Lu-177

Long-term Follow-up:

• Annual biochemical screening for 5-10 years
• Genetic counseling and family screening when indicated
• Surveillance imaging for high-risk features

Cushing Syndrome Complications:

Acute Complications:

• Diabetic ketoacidosis: From severe hyperglycemia
• Opportunistic infections: Due to immunosuppression
• Psychiatric emergencies: Severe depression, psychosis, suicidal ideation
• Cardiovascular events: Myocardial infarction, stroke

Chronic Complications:

• Cardiovascular: Accelerated atherosclerosis, congestive heart failure
• Musculoskeletal: Osteoporotic fractures, avascular necrosis
• Metabolic: Type 2 diabetes mellitus, metabolic syndrome
• Growth: Permanent growth retardation in children

[HIGH_YIELD] Mortality risk: 2-5 fold increased standardized mortality ratio, primarily from cardiovascular and infectious causes.

Recovery Timeline:

• Metabolic improvements: 3-12 months
• Bone density: 1-2 years
• Muscle weakness: 6-24 months
• Psychiatric symptoms: Variable, may persist

Addison Disease Complications:

Adrenal Crisis (Medical Emergency):

Clinical Features:

• Severe hypotension/shock
• Altered mental status
• Severe dehydration
• Hypoglycemia, hyperkalemia
• Abdominal pain, vomiting

Management Protocol:

1. Immediate: IV hydrocortisone 100mg bolus
2. Fluids: Normal saline 1-2L over first hour
3. Maintenance: Hydrocortisone 50-100mg IV q6-8h
4. Electrolytes: Monitor and correct hyponatremia, hyperkalemia
5. Precipitant: Identify and treat underlying cause

[CLINICAL_PEARL] Never delay steroid treatment for diagnostic testing in suspected adrenal crisis. Dexamethasone 4mg IV can be used if cortisol measurement needed.

Long-term Complications:

• Cardiovascular: Increased mortality from cardiovascular disease
• Autoimmune: Associated autoimmune conditions (thyroid, diabetes)
• Osteoporosis: From chronic glucocorticoid replacement
• Adrenal crisis: 5-10% annual incidence without proper education

Pheochromocytoma Complications:

Cardiovascular Complications:

• Hypertensive crisis: Malignant hypertension, stroke
• Cardiomyopathy: Catecholamine-induced (often reversible)
• Arrhythmias: Ventricular tachycardia, atrial fibrillation
• Myocardial infarction: From coronary vasospasm

Surgical Complications:

• Intraoperative crisis: Hypertension, arrhythmias during tumor manipulation
• Post-operative hypotension: From catecholamine withdrawal
• Bleeding: Due to friable, vascular tumors

Prognosis by Tumor Type:

Malignancy Predictors:

• Size >5-6 cm
• Extra-adrenal location
• SDHB gene mutations
• Invasive imaging features
• High proliferative index (Ki-67)

[HIGH_YIELD] Hereditary syndromes have higher malignancy risk: SDHB (30-50%), SDHD (5-15%), VHL (5-10%).

Long-term Surveillance:

• Biochemical: Annual catecholamine/metanephrine levels for 5-10 years
• Imaging: CT/MRI every 1-2 years for high-risk patients
• Genetic counseling: Family screening for hereditary syndromes
• Blood pressure monitoring: Hypertension may persist post-operatively in 25-50%

Overall prognosis depends on early diagnosis, appropriate treatment, and long-term surveillance for recurrence and associated complications.