Endocrine

Myxedema coma: recognition and management

Clinical Overview and When to Suspect Myxedema Coma

— Rare (~0.22/million/year) but mortality 30–60% even with aggressive therapy

— Predominantly elderly women in winter months

— Often the first presentation of long-standing untreated/undertreated hypothyroidism, or unmasked by a precipitant

— Infection (pneumonia, UTI, sepsis) — most common trigger

— Cold exposure, especially in winter

— CVA, MI, CHF, GI bleed, trauma, surgery

— Drugs: amiodarone, lithium, sedatives, opioids, anesthetics, diuretics, beta-blockers

— Noncompliance with levothyroxine, or recent discontinuation

— Hypothermic (<35.5°C), bradycardic, hypotensive, hypoventilating elderly patient with confusion or stupor

— History of thyroidectomy, radioactive iodine, autoimmune thyroid disease, neck irradiation, or a visible thyroidectomy scar with no medication list

— Hyponatremia + hypoglycemia + hypoventilation triad in an obtunded patient

— Pericardial or pleural effusions of unclear cause

— Profound deficiency of T3/T4 → reduced thermogenesis, decreased cardiac output, hypoventilation (blunted hypoxic/hypercapnic drive), reduced free-water clearance (SIADH-like), adrenal hyporesponsiveness

— Decompensation when a stressor exceeds the patient's already marginal metabolic reserve

Board pearl: Myxedema coma is a clinical diagnosis — do not wait for TSH/free T4 results before initiating empiric therapy. Mortality climbs sharply with each hour of delay, so suspicion in the right elderly hypothermic, hyponatremic, bradycardic patient is enough to start IV levothyroxine plus stress-dose hydrocortisone in parallel with the workup.

Definition: Decompensated, life-threatening hypothyroidism characterized by altered mental status, hypothermia, and multiorgan slowing — a misnomer because frank coma is uncommon and overt myxedema (non-pitting edema) is not required.

Epidemiology:

Classic precipitants to probe in the ED:

When to suspect at triage:

Pathophysiology snapshot:

Presentation Patterns and Key History

— Altered mental status (lethargy → stupor → rarely true coma; may present as psychosis, "myxedema madness")

— Hypothermia (often <35°C; a "normal" temp in this patient may actually be relative fever from infection)

— Precipitating illness or stressor

— Neuro: progressive somnolence over days–weeks, slow speech, ataxia, seizures (~25%), depressed reflexes with delayed relaxation phase (hung-up reflexes)

— Cardiac: fatigue, dyspnea on exertion, pedal edema, syncope

— Pulmonary: hypoventilation, CO₂ narcosis, sleep apnea worsening

— GI: constipation, ileus, anorexia, abdominal distension (megacolon)

— GU: oliguria, urinary retention from atonic bladder

— Derm: dry coarse skin, alopecia (lateral third of eyebrows — Queen Anne's sign), macroglossia, hoarseness

— Thyroid disease, thyroid surgery, RAI ablation, external-beam radiation to neck

— Hashimoto's, vitiligo, type 1 DM, Addison's (polyglandular autoimmune syndrome)

— Pituitary surgery, postpartum hemorrhage (Sheehan), head trauma → consider central hypothyroidism

— Medication reconciliation: levothyroxine dose, missed refills, recent switches between generic/brand, amiodarone, lithium, checkpoint inhibitors, interferon

— Recent infection, cold exposure, surgery, opioid or benzodiazepine use

Step 3 management: When the patient cannot speak, send EMS or family back for the pill bottles and pharmacy records. Finding an empty levothyroxine bottle or a discontinued refill instantly tightens the diagnosis and justifies empiric therapy. Document the source of history and time of last known well in the chart — this matters for stroke mimics and for medicolegal traceability of your empiric treatment decision.

Cardinal triad to anchor recognition:

System-by-system symptom review from collateral history:

Targeted history to elicit:

Time course clue: Symptoms typically evolve over weeks to months then crash acutely with a trigger — distinguish from a primary acute neurologic event

Physical Exam Findings and Hemodynamic Assessment

— Temperature: hypothermia (often 30–35°C); use a low-reading rectal thermometer, as standard probes underread

— HR: sinus bradycardia (40s–50s)

— BP: hypotension, narrow pulse pressure; diastolic HTN can paradoxically occur from systemic vasoconstriction

— RR: hypoventilation with hypercapnia and hypoxia

— SpO₂: low; ABG often reveals respiratory acidosis

— Puffy, doughy facies; periorbital edema; macroglossia

— Non-pitting pretibial myxedema (mucopolysaccharide deposition)

— Cool, dry, sallow, scaly skin; carotenemia (yellow palms/soles without scleral icterus)

— Thinning hair, loss of lateral eyebrows

— Thyroidectomy scar — always look

— Goiter (Hashimoto's) or no palpable thyroid (atrophic/post-ablative)

— Hoarse, slow speech

— Muffled heart sounds → suspect pericardial effusion; rarely tamponade

— Dullness at bases → pleural effusions (transudative)

— Bibasilar crackles if concomitant CHF

— Distension, hypoactive bowel sounds, fecal impaction, possible ileus or myxedema megacolon

— Ascites can occur

— Generalized hyporeflexia with delayed relaxation of ankle/biceps reflexes — pathognomonic feel

— Cerebellar ataxia, hung-up Achilles

— GCS ranges from drowsy to comatose; psychosis possible

— Output is low from bradycardia + decreased contractility; SVR is paradoxically elevated

— Fluid responsiveness is limited; vasopressors may be ineffective until thyroid hormone is replaced

Key distinction: Hypothermia with bradycardia + delayed-relaxation reflexes + macroglossia points to myxedema coma; hypothermia with shivering, tachycardia, and a clear environmental exposure points to primary environmental hypothermia — managed by rewarming alone, not hormone replacement.

Vital signs — the "everything is low" pattern:

General appearance:

HEENT/neck:

Cardiopulmonary:

Abdomen:

Neuro:

Hemodynamic assessment:

Diagnostic Workup — Initial Labs, Imaging, ECG

— TSH markedly elevated, free T4 low → primary hypothyroidism (most common)

— TSH low/normal with low free T4 → central (secondary/tertiary) hypothyroidism — implies pituitary/hypothalamic pathology

— Total T3 often very low (peripheral conversion impaired)

— Random serum cortisol and ACTH before giving hydrocortisone

— Coexisting adrenal insufficiency present in ~5–10% (autoimmune polyglandular, or central from panhypopituitarism)

— Hyponatremia (dilutional, SIADH-like) — often <130

— Hypoglycemia — check fingerstick immediately

— Elevated creatinine (decreased renal perfusion), elevated CK (myopathy, rhabdomyolysis), elevated LDH, AST

— Lactate may be elevated from poor perfusion

— Blood, urine, sputum cultures; CXR; UA; lactate; procalcitonin

— Low threshold for empiric broad-spectrum antibiotics

— Sinus bradycardia, low voltage (effusion), prolonged QT (torsades risk), flattened/inverted T waves, varying degrees of heart block

— CXR: cardiomegaly (effusion), pleural effusions, infiltrates

— CT head if focal deficits, trauma, or concern for stroke/pituitary mass

— Bedside echo if effusion suspected

CCS pearl: Order in parallel: fingerstick glucose, TSH, free T4, random cortisol, ACTH, CMP, CBC, ABG, lactate, blood/urine cultures, CXR, ECG, head CT. Then immediately move to empiric IV hydrocortisone → IV levothyroxine → passive rewarming → cautious fluid resuscitation. The clock matters more than confirmation.

Thyroid function tests — send before first hormone dose, do not wait for results:

Cortisol — critical:

Chemistry:

CBC: Normocytic or macrocytic anemia; leukocytosis may be blunted despite infection — absence of fever or leukocytosis does NOT rule out sepsis

ABG: Respiratory acidosis with hypoxemia; mixed picture if shock present

Cultures and infection workup:

ECG:

Imaging:

Toxicology: screen for sedatives, opioids, alcohol — frequent confounders or precipitants

Diagnostic Workup — Advanced and Confirmatory Studies

— Popoveniuc diagnostic score weights thermoregulatory dysfunction, CNS effects, GI, cardiovascular, metabolic abnormalities, and presence of a precipitant

— Score ≥60 highly suggestive; 25–59 risk of impending myxedema coma

— Do not let scoring delay treatment — it supports clinical gestalt

— Free T4 (low) and TSH (high) confirm primary disease

— If central hypothyroidism suspected: pituitary MRI, prolactin, FSH/LH, IGF-1, morning testosterone (men), 8 AM cortisol with ACTH stimulation test (once stabilized off hydrocortisone — typically delayed)

— Anti-TPO and anti-thyroglobulin antibodies (Hashimoto's) for outpatient confirmation of etiology

— Bedside transthoracic echo for pericardial effusion, ventricular function (often globally hypokinetic)

— Troponin if ischemia suspected — myxedema coma can mask classic MI presentation

— Serial ECGs for QT monitoring, especially after starting medications

— ABG to trend pCO₂ and pH; capnography if intubated

— Consider sleep study after recovery — high rate of comorbid OSA contributing to chronic hypoventilation

— EEG if seizures occur or status epilepticus suspected — diffuse slowing typical

— LP if meningitis cannot be excluded; remember opening pressure may be elevated from cerebral edema in severe cases

— Abdominal imaging if obstruction, megacolon, or ischemia suspected; avoid early surgery for ileus until thyroid replacement begins

— Aggressive search for occult source — UA + cultures, CXR, skin/decubitus exam, line evaluation; empiric antibiotics until cultures return

— Lithium level if applicable; amiodarone history (can cause hypo- or hyperthyroidism)

Board pearl: A low or inappropriately normal TSH in a clinically obvious myxedema coma patient is not reassurance — it signals central hypothyroidism, which mandates hydrocortisone before thyroid hormone to avoid precipitating adrenal crisis. Also pursue a pituitary MRI once stabilized.

Scoring system (helpful for borderline cases):

Confirmatory endocrine testing:

Cardiac evaluation:

Pulmonary:

Neurologic:

GI:

Infectious workup:

Drug levels:

Risk Stratification and First-Line Management Logic

— 1. Airway/breathing: Low threshold for intubation; respiratory failure is a leading cause of death. Hypercapnia and CO₂ narcosis develop insidiously.

— 2. Empiric hydrocortisone FIRST (before thyroid hormone) — 100 mg IV bolus, then 50–100 mg IV q6–8h. Levothyroxine alone can precipitate adrenal crisis if coexisting adrenal insufficiency.

— 3. IV levothyroxine — loading dose 200–400 mcg IV, then 50–100 mcg IV daily. Some protocols add T3 (liothyronine) 5–20 mcg IV load then 2.5–10 mcg q8h, especially if severe cardiac compromise (controversial; higher arrhythmia risk in elderly/CAD).

— 4. Passive external rewarming only — warm blankets, warm room. Avoid active rewarming (heating pads, warm IVF >40°C) which causes peripheral vasodilation → shock.

— 5. Treat the precipitant — empiric broad-spectrum antibiotics until cultures return, even without fever or leukocytosis.

— Cautious isotonic IVF; avoid fluid overload (poor cardiac reserve, SIADH risk)

— Vasopressors often refractory until thyroid hormone takes effect — norepinephrine first-line if needed

— Correct hypoglycemia with D50; avoid free water for hyponatremia (fluid restrict)

— Sedatives, opioids, benzodiazepines (prolonged metabolism, worsen hypoventilation)

— Aggressive sodium correction (risk of osmotic demyelination — Na⁺ <120 may need hypertonic saline 3% in small aliquots)

Step 3 management: Memorize the trio: hydrocortisone first → levothyroxine → passive rewarming, all while culturing and empirically treating infection. The single most testable trap is giving T4 before hydrocortisone in a patient with possible adrenal insufficiency.

All myxedema coma patients are ICU-level — there is no "moderate" version that belongs on a regular floor.

The five parallel priorities (start within the first hour):

Hemodynamic support:

Avoid:

Pharmacotherapy — First-Line Drug Regimen

— 100 mg IV bolus → 50–100 mg IV q6–8h

— Continue until adrenal insufficiency excluded (post-stabilization cosyntropin stim) or for full course if confirmed

— Taper over days once thyroid levels rising and patient stable

— Load 200–400 mcg IV (lower end for elderly, small frame, CAD, arrhythmia history)

— Maintenance 1.6 mcg/kg/day IV (≈75–100 mcg daily) until oral tolerated

— Convert to oral at ~75% of IV dose once GI function returns and patient extubated

— 5–20 mcg IV load, then 2.5–10 mcg IV q8h until clinical improvement

— Rationale: peripheral T4→T3 conversion impaired in critical illness

— Risk: tachyarrhythmia, ischemia — avoid or minimize in elderly, CAD, atrial fibrillation

— Current ATA guidance: combination T4+T3 reasonable in severe disease; T4 monotherapy acceptable

— Free T4 daily; TSH every 1–2 days (slow to fall)

— Continuous telemetry for arrhythmia, ischemia

— Serial mental status checks; expect improvement over 24–72 h

— Dextrose for hypoglycemia (D50 push, then D10 infusion)

— Empiric antibiotics: broad-spectrum (e.g., ceftriaxone ± vancomycin) until source identified

— Vasopressors: norepinephrine titrated to MAP ≥65; expect refractoriness until thyroid effect

— DVT prophylaxis (LMWH or heparin SC) — immobile, hypercoagulable risk

— Stress ulcer prophylaxis with PPI

— Sedatives, opioids, benzodiazepines, propofol bolus (hypotension)

— Amiodarone (worsens thyroid status); lithium

— Beta-blockers unless arrhythmia mandates

Board pearl: The #1 wrong answer is starting levothyroxine alone in a hypotensive obtunded hypothyroid patient. Hydrocortisone 100 mg IV always precedes or accompanies the T4 load, because untreated adrenal crisis is rapidly fatal and a single dose causes no harm if adrenal axis turns out intact.

Hydrocortisone (give first):

Levothyroxine (T4) — IV preferred:

Liothyronine (T3) — adjunct, controversial:

Monitoring during replacement:

Supportive pharmacology:

Drugs to STOP or AVOID:

Procedures and Advanced Supportive Management

— Indications for intubation: GCS deterioration, hypercapnia (pCO₂ >50 with acidosis), hypoxemia refractory to supplemental O₂, inability to protect airway

— Anticipate difficult airway — macroglossia, short neck, obesity, decreased neck mobility; have video laryngoscopy and surgical airway backup ready

— Use minimal sedation — etomidate (single dose acceptable despite adrenal concern, since hydrocortisone already given), avoid propofol bolus

— Expect prolonged ventilator dependence (days–weeks); plan for early tracheostomy if extubation fails by day 7–10

— Central venous access for vasopressors and frequent labs

— Arterial line for continuous BP and ABG sampling

— Avoid pulmonary artery catheter routinely; bedside echo guides volume status

— Passive external: warm blankets, room temp 24–26°C, head covering

— Warmed humidified ventilator circuit (40°C)

— Warmed IV fluids to body temperature (not hotter)

— Avoid: forced-air warmers on bare skin, immersion, heating pads — all cause vasodilation → shock

— Target rise of 0.5°C/hour

— Most are slowly accumulating, hemodynamically tolerated — treat the hypothyroidism, not the effusion

— Pericardiocentesis only for tamponade physiology

— Hyponatremia: fluid restrict to 1 L/day; hypertonic 3% saline only if seizures or Na⁺ <120 with symptoms; correct ≤8 mEq/L/24 h to avoid osmotic demyelination

— Hypoglycemia: D10 infusion after D50 push; recheck q1h

— Remove infected lines, drain abscesses, foley change; do not delay

— Early enteral feeding once ileus resolves; aspiration precautions

CCS pearl: On the simulated case, move the clock forward in short increments (15–30 min) during the first 4 hours — recheck mental status, vitals, glucose, and lab trends. Don't advance hours at a time until the patient is stable on T4, hydrocortisone, antibiotics, and rewarming is underway.

Airway management:

Hemodynamic procedures:

Rewarming protocol:

Pericardial effusion management:

Electrolyte management:

Source control for sepsis:

Nutrition:

Special Populations — Elderly and Renal/Hepatic Impairment

— Lower T4 loading dose — 100–200 mcg IV (not 400 mcg) given high prevalence of occult CAD and arrhythmia

— Avoid or minimize T3 — risk of MI, atrial fibrillation, ventricular arrhythmia

— Continuous telemetry mandatory; serial troponins and ECGs

— Watch for delirium during recovery — taper sedatives aggressively

— Higher risk of pressure ulcers, aspiration pneumonia, DVT during prolonged immobility

— Polypharmacy review: discontinue amiodarone if possible, reassess all sedatives

— Start with lower T4 dose (50–100 mcg IV load), titrate slowly

— Maintain beta-blocker only if active arrhythmia or ischemia

— If acute coronary syndrome coexists, treat MI per usual protocols — do not withhold aspirin or anticoagulation, but coordinate with cardiology

— Levothyroxine dosing not affected by GFR

— Hyponatremia management more delicate — slower correction, watch volume

— Adjust antibiotic and vasopressor dosing per CrCl

— Many of these patients have AKI from hypoperfusion — usually reverses with hemodynamic and thyroid recovery

— Levothyroxine metabolism partially hepatic but dose unchanged

— Hypoalbuminemia alters free hormone interpretation — trust free T4 over total T4

— Coagulopathy and encephalopathy may confound mental status assessment

— Reduced ejection fraction common; furosemide cautiously, as overdiuresis worsens hypotension

— Inotropes (dobutamine) sometimes needed bridging until thyroid hormone takes effect

— Goals-of-care conversation early — mortality remains 30–40% even with optimal care

— Engage family, surrogate decision-makers, palliative care concurrently with aggressive treatment

Key distinction: In a 35-year-old, load levothyroxine 300–400 mcg IV; in an 82-year-old with prior CABG, load 100–200 mcg and skip T3. The patient's cardiovascular reserve drives the dose, not just body weight.

Elderly (the modal patient):

CAD/known ischemic heart disease:

Renal impairment:

Hepatic impairment:

Heart failure overlap:

Frailty considerations:

Special Populations — Pregnancy and Other Subgroups

— Untreated/undertreated hypothyroidism in pregnancy increases miscarriage, preeclampsia, abruption, stillbirth, low birth weight, and impaired fetal neurodevelopment

— Myxedema coma in pregnancy: same algorithm — hydrocortisone, IV levothyroxine, passive rewarming, treat precipitant

— Levothyroxine requirements rise 30–50% during pregnancy; postpartum requirements drop back

— Fetal monitoring with continuous tocodynamometry; involve OB and MFM early

— Postpartum hemorrhage history? Suspect Sheehan syndrome with combined central hypothyroidism + adrenal insufficiency → hydrocortisone is non-negotiable first

— Postpartum thyroiditis can transition through hyper- then hypothyroid phases; severe decompensation rare but reported

— Lithium- or amiodarone-treated patients may decompensate postpartum due to dose shifts

— Extremely rare; usually congenital hypothyroidism missed at newborn screening or in resource-limited settings

— Weight-based dosing: levothyroxine 10–15 mcg/kg/day; hydrocortisone 1–2 mg/kg q6h

— Pediatric ICU and pediatric endocrinology mandatory

— Especially at risk if levothyroxine interrupted (NPO, surgery, GI illness, malabsorption from bariatric surgery, celiac, PPI use)

— Always reconcile and resume thyroid replacement perioperatively; IV equivalent is 50–75% of oral dose

— Checkpoint inhibitors (pembrolizumab, nivolumab, ipilimumab) cause autoimmune thyroiditis and hypophysitis — concurrent adrenal insufficiency common

— Always check both thyroid and cortisol axes in decompensated cancer patients on these drugs

— Oral absorption impaired; switch to IV or liquid formulations

— Educate on separation from calcium, iron, PPIs, sucralfate

Step 3 management: A pregnant patient with severe hypothyroidism needs higher maintenance levothyroxine (often pre-pregnancy dose +30%) and TSH targeted to trimester-specific ranges (typically <2.5 in first trimester) — failure to escalate dose is a high-yield outpatient miss.

Pregnancy (rare but high-stakes):

Postpartum patients:

Pediatric:

Post-thyroidectomy / post-RAI patients:

Immunotherapy-associated:

Bariatric/short-bowel patients:

Complications and Adverse Outcomes

— Overall mortality 30–60% despite optimal therapy; predictors include older age, lower GCS, higher APACHE, persistent hypothermia, need for mechanical ventilation, sepsis, bradycardia <50, hypotension requiring vasopressors

— Hypoventilation → CO₂ narcosis → respiratory arrest

— Aspiration pneumonia (depressed gag, ileus, NG misplacement)

— Prolonged ventilator weaning; ventilator-associated pneumonia

— Pleural effusions limiting tidal volume

— Bradyarrhythmias, heart block, torsades from prolonged QT

— Iatrogenic MI or arrhythmia from aggressive T3/T4 dosing, especially in elderly with CAD

— Pericardial effusion (rarely tamponade)

— Refractory hypotension until hormone effect

— Seizures (25%), status epilepticus

— Cerebral edema in severe hyponatremia

— Osmotic demyelination syndrome if Na⁺ corrected >8–10 mEq/L/24 h

— Persistent encephalopathy/dementia features may take weeks to clear

— Persistent hyponatremia; SIADH

— Hypoglycemia (especially with adrenal insufficiency)

— Rhabdomyolysis with AKI

— Paralytic ileus, megacolon, perforation if missed

— Stress ulceration and GI bleeding

— Underlying sepsis often the precipitant and the killer; fever and leukocytosis blunted, so clinical suspicion must remain high

— Line infections during prolonged ICU stay

— Aspiration pneumonia, decubitus ulcers, UTIs from immobility

— Active rewarming → vasodilatory shock

— Excess IVF → pulmonary edema, worsened hyponatremia

— Sedative accumulation due to slowed metabolism

Board pearl: Two preventable killers in this disease are (1) giving levothyroxine without hydrocortisone in a patient with unrecognized adrenal insufficiency, and (2) active external rewarming causing peripheral vasodilation and circulatory collapse. Both are favorite distractor traps.

Mortality drivers:

Respiratory complications:

Cardiovascular complications:

Neurologic:

Metabolic:

GI:

Infectious:

Iatrogenic complications:

When to Escalate Care — ICU, Consult, and Triage

— No ED-to-floor admissions; even "mild" cases warrant continuous monitoring during the first 24–72 hours of hormone replacement

— Endocrinology — confirm dosing strategy, especially for central hypothyroidism, pregnancy, pediatric, or unusual etiologies

— Critical care/intensivist — airway, hemodynamics

— Infectious disease if source unclear or immunocompromised

— Cardiology if ACS, arrhythmia, or significant pericardial effusion

— OB/MFM for any pregnant patient

— Palliative care early for frail elderly with poor baseline functional status — high mortality justifies parallel goals-of-care conversation

— GCS ≤8, declining mental status, pCO₂ rising, hypoxemia, inability to protect airway

— No ICU, no endocrinology backup, no IV levothyroxine on formulary (some smaller hospitals stock only oral)

— Pregnant patient

— Pediatric patient

— Need for advanced cardiac support (mechanical circulatory support rarely needed)

— Suspected pituitary mass requiring neurosurgical evaluation

— Administer first dose of hydrocortisone and IV levothyroxine before transport — do not delay for receiving facility

— Secure airway prior to transport if borderline respiratory status

— Document vitals, labs, medications given, and time-stamps

— Direct physician-to-physician handoff using a structured tool (e.g., SBAR)

— Hemodynamically stable, off vasopressors 24+ h

— Extubated, normothermic, mental status improving

— Free T4 trending up, electrolytes corrected

— Tolerating oral levothyroxine

— Then step down to telemetry/floor

Step 3 management: On Step 3, the "next best step" for a stabilized myxedema coma patient still in the ED is ICU admission with endocrinology consultation, not transfer to the floor — even if the patient looks better after the first hydrocortisone and levothyroxine doses.

Disposition: ICU, every time.

Early consults to call from the ED:

Indications for emergent intubation:

Transfer criteria from community ED to tertiary center:

Stabilization before transfer:

De-escalation criteria:

Key Differentials — Same-Category (Endocrine/Metabolic) Causes

— Shares hypotension, hyponatremia, hypoglycemia, altered mental status, weakness

— Differentiating features: hyperpigmentation (primary Addison's), eosinophilia, hyperkalemia (primary only), normal-to-elevated temperature, faster onset

— Often coexists with myxedema coma — treat both

— Diaphoresis, tachycardia, tremor, seizures — but in elderly or beta-blocked patients can present as isolated obtundation

— Differentiates by immediate response to dextrose; thyroid panel normal

— Hyperglycemia, hyperosmolarity, anion gap acidosis

— Lacks the bradycardia and hypothermia of myxedema; tachycardia and Kussmaul breathing more typical

— Overlapping confusion and seizures; serum osmolality and urine studies differentiate

— Myxedema causes hyponatremia via reduced free-water clearance — TSH is part of any hyponatremia workup

— Sudden headache, ophthalmoplegia, visual field defect; central hypothyroidism + adrenal insufficiency + hypogonadism

— MRI pituitary; hydrocortisone first, then thyroid

— Environmental, sepsis, hypoglycemia, alcohol intoxication, drug overdose (barbiturates, phenothiazines), Wernicke encephalopathy

— Thyroid panel and history distinguish

— Symptoms without the decompensation triad — outpatient initiation of levothyroxine at 1.6 mcg/kg/day oral, not emergency dosing

— Amiodarone-induced hypothyroidism, lithium-induced, immune checkpoint inhibitor thyroiditis — can precipitate decompensation if severe

Key distinction: Adrenal crisis features hyperkalemia and hyperpigmentation with hypotension; myxedema coma features hypothermia, bradycardia, hung-up reflexes, and macroglossia. When both axes fail (polyglandular autoimmune type 2 or panhypopituitarism), expect a blend — always replace cortisol first.

Adrenal crisis (primary or secondary):

Severe hypoglycemia:

Diabetic ketoacidosis / HHS:

Severe hyponatremia from SIADH or psychogenic polydipsia:

Pituitary apoplexy / panhypopituitarism:

Hypothermia from other causes:

Severe hypothyroidism without coma (compensated):

Drug-induced hypothyroid states:

Key Differentials — Other-Category Causes of Obtundation + Hypothermia

— Elderly, immunocompromised, or end-of-life patients may present with hypothermia rather than fever

— Procalcitonin, lactate, blood cultures; broad-spectrum antibiotics

— Can coexist with and precipitate myxedema coma

— History of exposure, intact thyroid axis

— Active rewarming appropriate here (unlike in myxedema)

— Cardiac arrhythmias with Osborn (J) waves on ECG

— Opioids (pinpoint pupils, respiratory depression, naloxone reversal)

— Benzodiazepines, barbiturates, alcohol

— Phenothiazines, anticholinergics — can disrupt thermoregulation

— Tox screen, anion gap, osmolar gap

— Ischemic stroke (especially brainstem), intracerebral or subarachnoid hemorrhage, subdural hematoma

— Focal deficits, asymmetric exam, abnormal pupils — head CT first

— Hypothalamic lesions disrupt thermoregulation directly

— Fever may be absent in elderly; LP if any doubt

— Empiric antibiotics ± antivirals

— Asterixis, fetor hepaticus, known cirrhosis; ammonia elevated

— Lactulose, rifaximin

— Severe AKI/CKD, asterixis, pericardial rub

— BUN >100, dialysis indication

— Triad of confusion, ophthalmoplegia, ataxia in alcoholic or malnourished patient

— Thiamine 500 mg IV before glucose

— Always check fingerstick first; D50 is diagnostic and therapeutic

— "Myxedema madness" — psychotic features predate the coma; psychiatric history may mislead

Board pearl: The reflex 5-second bedside checks in any obtunded hypothermic elder are: fingerstick glucose, rectal temperature with low-reading thermometer, pupils, gag reflex, ECG, and a quick neck inspection for a thyroidectomy scar. The scar is the single most diagnostic physical finding you can spot in 3 seconds.

Sepsis with hypothermic phenotype:

Environmental hypothermia:

Drug/toxin overdose:

CNS catastrophe:

Meningitis/encephalitis:

Hepatic encephalopathy:

Uremic encephalopathy:

Wernicke encephalopathy:

Hypoglycemic coma:

Profound hypothyroidism with depression-induced catatonia:

Secondary Prevention, Discharge Medications, and Long-Term Plan

— Once tolerating PO, switch at 75–80% of the IV dose

— Typical maintenance: 1.6 mcg/kg/day oral; elderly start lower (25–50 mcg/day) and titrate

— Take on empty stomach, 30–60 min before breakfast, with water only

— Separate from calcium, iron, PPIs, sucralfate, bile acid sequestrants, soy by at least 4 hours

— If adrenal axis confirmed intact (post-stim cosyntropin >18 mcg/dL), discontinue

— If adrenal insufficiency confirmed, transition to maintenance hydrocortisone 15–25 mg/day in divided doses + fludrocortisone if primary

— Patient education on stress-dose steroids, medical alert bracelet, emergency injection kit

— Complete antibiotic course for any infection

— Discontinue offending drugs (amiodarone alternatives, lithium dose review)

— Vaccinate: influenza, pneumococcal, COVID, RSV per age

— Identify reason for original noncompliance — cost, cognitive impairment, polypharmacy, depression, lack of follow-up

— Engage pharmacy for 90-day refills, mail-order, pill organizers

— Family/caregiver education on signs of relapse

— TPO antibodies (Hashimoto's confirmation)

— Pituitary MRI if central hypothyroidism suspected

— Other autoimmune screening (celiac, T1DM, pernicious anemia, Addison's) given polyglandular risk

— Avoid OTC iodine-containing supplements, kelp products

— Pregnancy planning — preconception TSH optimization to <2.5 mIU/L

— Driving restrictions until cognitive recovery documented

Step 3 management: Do not discharge without a confirmed primary care follow-up appointment within 1–2 weeks, a written medication list, and a TSH recheck scheduled at 6 weeks (steady state on levothyroxine). The post-discharge gap is when relapse happens.

Transition from IV to oral levothyroxine:

Hydrocortisone wean:

Address the precipitant:

Adherence support:

Etiology workup completed outpatient:

Lifestyle and counseling:

Follow-Up, Monitoring Parameters, and Counseling

— TSH and free T4 at 6 weeks after any dose change or initiation (reflects new steady state)

— Once stable, recheck every 6–12 months lifelong

— More frequent in pregnancy (every 4 weeks through mid-pregnancy), after starting interfering meds, or with new GI/absorption issues

— General adult: 0.5–4.5 mIU/L (or local reference)

— Pregnant: trimester-specific, generally <2.5 in T1, <3.0 in T2/T3

— Elderly >70: upper-normal acceptable (e.g., 4–6) to avoid overtreatment-related AF and osteoporosis

— Central hypothyroidism: titrate to free T4 mid-to-upper-normal range, NOT TSH (which is unreliable here)

— Fatigue, weight gain, cold intolerance, constipation, depression, hair changes

— Palpitations, tremor, anxiety, weight loss, heat intolerance, insomnia, atrial fibrillation, osteoporosis (long-term)

— Starting calcium, iron, PPI, estrogen — may need dose adjustment

— New amiodarone, lithium, tyrosine kinase inhibitors — recheck TSH within 6 weeks

— Cardiovascular: lipid panel, BP, glucose — hypothyroidism contributes to dyslipidemia

— Bone density in elderly post-decompensation if any over-replacement history

— Mood: screen for depression at each visit, common in chronic hypothyroidism

— ICU-acquired weakness common — PT/OT referral

— Cognitive recovery may take weeks to months; neuropsych testing if persistent deficits

— Aspiration risk evaluation (SLP) before fully oral diet at home

— Pulmonary rehab if prolonged ventilator dependence

— Never stop levothyroxine abruptly

— Bring all medication bottles to every visit

— Carry a wallet card listing thyroid history and any steroid dependence

Board pearl: 6 weeks is the magic interval to recheck TSH after any levothyroxine dose change — earlier rechecks reflect non-steady-state values and lead to incorrect titration. This is a recurring Step 3 outpatient management point.

Monitoring cadence after discharge:

Target TSH range:

Signs of under-replacement to counsel about:

Signs of over-replacement:

Drug-interaction counseling:

Comorbidity surveillance:

Rehab needs after ICU stay:

Patient/caregiver education:

Ethical, Legal, and Patient Safety Considerations

— Patient lacks capacity at presentation — proceed under emergency doctrine (implied consent for life-saving therapy)

— Identify and contact surrogate (spouse, adult child, durable power of attorney) as soon as possible; document attempts

— For invasive procedures (intubation, central line, LP), document the emergency rationale and surrogate notification

— Mortality 30–60% — within the first 24 hours, hold a structured family meeting to clarify advance directives, code status, and limits of escalation

— Frail elderly with poor baseline functional status: align aggressive ICU therapy with patient values; involve palliative care concurrently, not as a "last resort"

— Levothyroxine omission at hospital admission is a leading contributor to in-hospital myxedema decompensation — verify and continue on every admission, including NPO patients (give IV if needed)

— Bariatric surgery and short-bowel patients require formulation review (liquid or IV)

— Suspected elder neglect if presentation reflects prolonged untreated chronic disease, missed appointments, and inadequate caregiver support — report to Adult Protective Services per state law

— Document specific findings supporting concern (medication noncompliance pattern, hygiene, home conditions per EMS)

— Discharge to SNF without clear thyroid replacement orders is a high-error zone

— Use structured handoff (medication list with doses and routes, follow-up appointments, TSH recheck date)

— Provide patient and family with written instructions and a teach-back confirmation

— Door-to-hydrocortisone time and door-to-levothyroxine time can be tracked as institutional quality measures

— Sentinel event review if a patient on chronic levothyroxine decompensates during hospitalization for an unrelated issue — usually traces to missed doses or NPO oversight

— IV levothyroxine is expensive and sometimes restricted; advocate for stocking in any ED expected to manage critically ill endocrine patients

Step 3 management: A nursing home patient on chronic levothyroxine who presents in myxedema coma after weeks of "not taking meds well" warrants both clinical stabilization and an APS report for suspected neglect — and a discharge plan that does not return the patient to the same unsupervised setting without intervention.

Informed consent in obtundation:

Goals-of-care conversations:

Medication reconciliation as a safety issue:

Mandatory reporting:

Transitions of care risks:

Quality and safety metrics:

Pharmacy formulary issue:

High-Yield Associations and Rapid-Fire Clinical Facts

Board pearl: If a stem mentions delayed relaxation of Achilles reflex and hypothermia, the diagnosis is myxedema coma until proven otherwise — even before the labs come back.

The "hypo-everything" picture: Hypothermia, hypotension, hypoventilation, hyponatremia, hypoglycemia, hyporeflexia (with delayed relaxation), hypoactive bowel sounds, low cardiac output

Pathognomonic finding: Delayed relaxation phase of deep tendon reflexes (especially Achilles) — "hung-up reflexes"

Skin signs: Carotenemia (yellow palms/soles, white sclera), pretibial non-pitting myxedema, loss of lateral eyebrows (Queen Anne's sign), macroglossia, periorbital puffiness

ECG signs: Sinus bradycardia, low voltage, prolonged QT, flattened/inverted T waves, occasional torsades

Lab signature: ↑TSH, ↓free T4, ↓Na⁺, ↓glucose, ↑CK, ↑creatinine, ↑LDH, ↑cholesterol; macrocytic anemia

Top precipitants (memorize): Infection > cold exposure > stroke/MI > medication noncompliance > sedatives/opioids > surgery/trauma > GI bleed

Drugs that cause or worsen hypothyroidism: Amiodarone, lithium, interferon-α, tyrosine kinase inhibitors (sunitinib), checkpoint inhibitors, iodine excess, antithyroid drugs

Mortality 30–60% even with optimal therapy; predictors of death: age, GCS, persistent hypothermia, vasopressor requirement, sepsis

Hydrocortisone before T4 — always

Passive rewarming only — never active external

IV levothyroxine loading dose: 200–400 mcg adult; lower in elderly/CAD

6-week TSH recheck after dose change

Levothyroxine timing: 30–60 min before breakfast, separated from calcium, iron, PPI

Pregnancy: Dose increases 30–50%; trimester-specific TSH targets

Polyglandular autoimmune syndromes: Hashimoto's + Addison's + T1DM + vitiligo + pernicious anemia (PAS-II)

Central hypothyroidism clue: Low/normal TSH with low free T4 → MRI pituitary, check cortisol; titrate by free T4 not TSH

Sheehan syndrome: Postpartum hemorrhage → panhypopituitarism → may present years later as myxedema coma

Don't sedate aggressively — drug metabolism dramatically slowed

The thyroidectomy scar is the highest-yield exam finding for an unconscious patient

Order of operations: ABCs → glucose → cortisol/TSH/T4 drawn → hydrocortisone → levothyroxine → cultures → empiric antibiotics → passive rewarming → ICU

Board Question Stem Patterns

— 72-year-old woman brought from home in winter; found unresponsive on couch; T 33.8°C, HR 48, BP 88/54, RR 8. Dry coarse skin, periorbital puffiness, thyroidectomy scar. Na 124, glucose 52. Next best step? → IV hydrocortisone, then IV levothyroxine, ICU admission, passive rewarming, empiric antibiotics. The trap answer is "IV levothyroxine alone" or "active rewarming with warm IVF and Bair Hugger."

— 58-year-old woman with Hashimoto's, ran out of levothyroxine 3 months ago. Confused, bradycardic, hyporeflexic with delayed relaxation. Best initial test? → TSH, free T4, cortisol, glucose. Best initial treatment? → Hydrocortisone + IV levothyroxine.

— Postpartum hemorrhage 8 years ago; never resumed menses; now obtunded, hypotensive. TSH 0.8, free T4 0.3. Best next step? → Hydrocortisone first (panhypopituitarism with adrenal insufficiency), then T4. Order pituitary MRI.

— Patient on amiodarone for 2 years now somnolent and bradycardic; TSH 95. Mechanism? Iodine-induced (Wolff–Chaikoff with failure to escape). Treat as myxedema coma; discuss alternatives to amiodarone with cardiology.

— Hypothyroid patient kept NPO after hip fracture surgery; levothyroxine held for 5 days; develops obtundation and hypothermia POD 4. Lesson: Always continue levothyroxine perioperatively; convert to IV (50–75% of oral dose) if NPO.

— 28-year-old at 14 weeks gestation, hypothyroid on levothyroxine 100 mcg, presents obtunded. Action: Continue/increase levothyroxine, hydrocortisone, fetal monitoring, MFM. TSH target <2.5.

— Tempts you with "warm saline bolus and forced-air warming." Correct answer: Passive rewarming only.

— Stable after 5 days of ICU therapy. Best follow-up? TSH in 6 weeks, PCP visit within 1–2 weeks, written instructions, medication reconciliation, APS referral if neglect suspected.

— Asks about NNT or mortality reduction of early hydrocortisone — recognize that prospective RCT data are limited, expert consensus drives practice.

Step 3 management: When the stem describes a hypothermic, bradycardic, hyponatremic elderly woman with a thyroidectomy scar, the correct answer almost always contains "administer IV hydrocortisone and IV levothyroxine, admit to ICU."

Classic stem 1 — the winter ED case:

Classic stem 2 — the medication noncompliance case:

Stem 3 — central hypothyroidism trap:

Stem 4 — drug-induced:

Stem 5 — surgical/perioperative:

Stem 6 — pregnancy:

Stem 7 — the "wrong rewarming" distractor:

Stem 8 — discharge planning:

Stem 9 — biostatistics overlay:

One-Line Recap

Myxedema coma is a clinical, life-threatening diagnosis in a hypothermic, hyponatremic, bradycardic, obtunded patient with chronic hypothyroidism, treated empirically with IV hydrocortisone first, then IV levothyroxine, passive rewarming, empiric antibiotics, ICU admission, and an aggressive search for the precipitant — never delayed for confirmatory labs.

Board pearl: The single most testable concept is the order: hydrocortisone → levothyroxine → passive rewarming → antibiotics → ICU. Get the order right, and the question is yours.

Recognize: Hypothermia + bradycardia + altered mental status + delayed-relaxation reflexes + thyroidectomy scar/known hypothyroidism + precipitant (infection, cold, medication lapse, drugs, surgery). Hyponatremia, hypoglycemia, hypercapnia, and elevated CK reinforce the picture; mortality 30–60%.

Treat in this exact order: (1) ABCs with low threshold for intubation, (2) draw TSH/free T4/cortisol/ACTH/glucose/lactate/cultures, (3) IV hydrocortisone 100 mg before any thyroid hormone, (4) IV levothyroxine 200–400 mcg load → 50–100 mcg/day (lower in elderly/CAD; consider T3 cautiously), (5) passive rewarming only, (6) empiric broad-spectrum antibiotics, (7) cautious isotonic fluids and dextrose, (8) ICU admission.

Avoid the traps: Active external rewarming (vasodilatory shock), levothyroxine without hydrocortisone (adrenal crisis), sedatives/opioids (CO₂ narcosis), rapid hyponatremia correction (osmotic demyelination), aggressive T3 in elderly/CAD (arrhythmia, MI), discharging without scheduled TSH recheck at 6 weeks.

Long-term: Identify and treat etiology (Hashimoto's, central, drug-induced, post-ablative); transition to oral levothyroxine at 75–80% of IV dose; PCP follow-up in 1–2 weeks; TSH in 6 weeks; address adherence, polypharmacy, and social drivers; APS referral if neglect; pregnancy and perioperative dose adjustments are recurring high-yield management points.