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Can you explain each concisely

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Here is a concise explanation of each condition, its first-line test, and why those confirmatory/imaging steps are used:

1. Primary Aldosteronism

What it is: Excess aldosterone production (usually from an adrenal adenoma or bilateral hyperplasia) causing hypertension and hypokalemia.
  • ARR >30: Aldosterone:Renin Ratio — high aldosterone with suppressed renin signals autonomous secretion.
  • CT adrenal: Looks for a unilateral adenoma (Conn's adenoma).
  • AVS (adrenal vein sampling): Gold standard to distinguish unilateral vs. bilateral disease before surgery.
  • Saline infusion test: Failure of aldosterone to suppress after IV saline confirms the diagnosis.

2. Pheochromocytoma

What it is: Catecholamine-secreting tumor of the adrenal medulla (or extra-adrenal), causing episodic hypertension, headache, sweating, palpitations.
  • 24h urine metanephrines/catecholamines & plasma metanephrines: Detect excess catecholamine metabolites; plasma metanephrines are the most sensitive test.
  • CT/MRI adrenal: Localizes the tumor.
  • MIBG scan: Radiolabeled tracer taken up by chromaffin tissue — used when metastatic or extra-adrenal disease is suspected.

3. Cushing's Syndrome

What it is: Chronic cortisol excess — most commonly from a pituitary ACTH-secreting adenoma (Cushing's disease), adrenal tumor, or ectopic ACTH.
  • 24h urine free cortisol: Measures total daily cortisol output.
  • Overnight 1mg DST (Dexamethasone Suppression Test): Normal cortisol suppresses to <50 nmol/L; failure to suppress = hypercortisolism.
  • CRH stimulation + IPSS: Differentiates pituitary source from ectopic ACTH by sampling venous drainage of the pituitary directly.
  • Pituitary MRI: Looks for a pituitary microadenoma.

4. Renovascular HTN

What it is: Hypertension caused by renal artery stenosis (usually atherosclerotic or fibromuscular dysplasia), triggering the renin-angiotensin system.
  • Renal Doppler USG: Non-invasive screening; detects elevated flow velocity across a stenosis.
  • Captopril renogram: ACE inhibitor worsens GFR in the affected kidney — a nuclear scan shows asymmetric perfusion.
  • MR/CT angiography: Visualizes the stenosis directly.
  • DSA (Digital Subtraction Angiography): Gold standard; also allows simultaneous intervention (angioplasty/stenting).

5. Coarctation of Aorta

What it is: Congenital narrowing of the aorta (typically at the ductus arteriosus), causing upper-limb hypertension with weak/delayed femoral pulses.
  • BP in 4 limbs: Upper > lower limb BP gradient >20 mmHg is the key clinical sign.
  • CXR: Shows rib notching (from dilated intercostal collaterals) and the classic "3 sign" (indentation at the coarctation site).
  • Echocardiogram: Assesses gradient across the coarctation and associated defects (e.g., bicuspid aortic valve).
  • CT/MRI aortogram: Defines anatomy pre-intervention.

6. Sleep Apnea

What it is: Repetitive upper airway collapse during sleep causing hypoxia, poor sleep quality, and secondary hypertension (via sympathetic activation).
  • Berlin questionnaire / Epworth Sleepiness Scale: Validated screening tools for risk stratification.
  • Polysomnography (PSG): Overnight sleep study measuring AHI (apnea-hypopnea index) — gold standard for diagnosis.

7. Hypothyroidism

What it is: Insufficient thyroid hormone, leading to hypertension (usually diastolic), fatigue, weight gain, cold intolerance.
  • TSH (↑): The pituitary releases more TSH to compensate for low T4 — elevated TSH is the earliest and most sensitive marker.
  • Free T4 (↓): Confirms overt hypothyroidism.
  • Anti-TPO antibodies: Positive in Hashimoto's thyroiditis, the most common cause.

8. Acromegaly

What it is: GH excess from a pituitary adenoma causing acral/soft tissue overgrowth, hypertension, diabetes, and organomegaly.
  • IGF-1 level: GH stimulates liver to produce IGF-1; it reflects integrated GH secretion and is the best screening test.
  • GH suppression test (oral glucose): GH should suppress to <1 ng/mL after a 75g glucose load; failure confirms acromegaly.
  • Pituitary MRI: Localizes the adenoma.

9. Renal Parenchymal / CKD

What it is: Chronic kidney disease is the most common cause of secondary hypertension overall, due to sodium retention, RAAS activation, and reduced vasodilator production.
  • eGFR: Estimates kidney filtration function; <60 mL/min/1.73m² defines CKD.
  • Urine ACR (albumin:creatinine ratio): Detects albuminuria, a marker of glomerular damage.
  • Urine microscopy: Identifies casts/RBCs suggesting active glomerulonephritis.
  • Renal biopsy: Required when glomerulonephritis is suspected to guide treatment.
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