Endo: Syndrome of Inappropriate ADH (SIADH): Free MSRA Podcast

🎧 FREE MSRA PODCAST – SIADH: Dilutional Danger, Diagnosis & Treatment EssentialsIn this essential revision episode, we unpack Syndrome of Inappropriate Antidiuretic Hormone (SIADH) – a frequently examined cause of hyponatraemia that’s tricky but high-yield. You’ll learn to identify it quickly, avoid dangerous pitfalls, and confidently manage it using a structured approach.🧠 Key Learning Points📌 Definition• SIADH = excessive antidiuretic hormone (ADH) → water retention → dilutional hyponatraemia• Blood becomes diluted, but volume appears normal (euvolaemia)• Triad: ↓ sodium, ↑ urine osmolality, euvolaemia📌 Causes (Mnemonic: TCPM)Tumours: esp. small cell lung cancer (produces ectopic ADH)CNS disorders: meningitis, stroke, head injuryPulmonary disease: pneumonia, TB, asthmaMedications: SSRIs, carbamazepine, TCAs, antipsychotics📌 Pathophysiology• Excess ADH → collecting ducts reabsorb too much water• Result: serum sodium falls due to dilution• Urine remains inappropriately concentrated despite low serum osmolality• Can be due to ectopic ADH secretion or renal hypersensitivity to ADH📌 Differential Diagnosis (Mnemonic: HARD)• Hypothyroidism• Adrenal insufficiency (Addison’s)• Renal dysfunction• Diuretics (esp. thiazides)📌 Clinical Features• Symptoms depend on sodium level & speed of drop: – Mild: fatigue, nausea, headache – Moderate: confusion, muscle cramps – Severe: seizures, coma• Often no oedema or signs of overload (euvolaemic)📌 Investigations🧪 Bloods:• ↓ Serum sodium• ↓ Serum osmolality• Normal renal, adrenal, thyroid function💧 Urine Tests:• ↑ Urine sodium >30 mmol/L• ↑ Urine osmolality >100 mOsm/kg• Rule out other causes with: TSH, cortisol, U&Es🖼️ Imaging:• Chest X-ray / CT → rule out lung malignancy• Brain MRI if CNS cause suspected📌 Management1️⃣ Fluid restriction (mainstay): typically <1L/day2️⃣ Hypertonic saline (e.g. 3%) for severe/symptomatic cases – Correct slowly to avoid osmotic demyelination syndrome (ODS)3️⃣ Furosemide + salt tablets in some cases4️⃣ Treat underlying cause (e.g. stop SSRIs, manage cancer)5️⃣ Tolvaptan (vasopressin antagonist) for resistant or chronic cases6️⃣ Patient education: understanding fluid restriction and warning signs📌 Prognosis & Complications• If the cause is reversible (e.g. medication/infection), outcome is excellent• Chronic or malignancy-linked SIADH has a prognosis tied to the underlying condition• Major risks: – Severe hyponatraemia → seizures, coma – ODS from rapid sodium correction – Rarely, pulmonary oedema or arrhythmias📎 More MSRA Resources for SIADH📝 Revision Notes:https://www.passthemsra.com/topic/syndrome-of-inappropriate-adh-siadh-revision-notes/🧠 Flashcards:https://www.passthemsra.com/topic/syndrome-of-inappropriate-adh-siadh-flashcards/💬 Accordion Q&A Notes:https://www.passthemsra.com/topic/syndrome-of-inappropriate-adh-siadh-accordion-qa-notes/🚀 Rapid Quiz:https://www.passthemsra.com/topic/syndrome-of-inappropriate-adh-siadh-rapid-quiz/🎓 Full Endocrinology Course:https://www.passthemsra.com/courses/endocrinology-for-the-msra/#MSRA #SIADH #Hyponatraemia #MSRARevision #MSRAFlashcards #PassTheMSRA #EndocrinologyMSRA #Tolvaptan #MedicalPodcast #MSRAQuestionBank #ClinicalMedicine #OsmoticDemyelination #FreeWaterRetention