Fatigue, cold, weight gain, constipation, hyponatremia
Confirm: Free T4 low + TSH high (Hashimoto → anti-TPO)
Treat: Levothyroxine 1.6 µg/kg/day PO empty stomach; start low (25–50 µg) in elderly/CAD; recheck TSH q6wk
Myxedema coma → IV levothyroxine + hydrocortisone (rule out adrenal insufficiency first — adrenal crisis can occur with ANY glucocorticoid route incl. inhaled/topical); passive rewarming + treat precipitant
Order set
- TSH, free T4
- Anti-TPO
- Lipids, FBC
- Cortisol if adrenal concern
Criteria
AdmitMyxoedema coma
ICUMyxoedema coma (hypothermia, ↓GCS, shock)
VasopressorsRefractory hypotension in myxoedema
DischargeLevothyroxine started, stable, TSH recheck plan
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Myxoedema coma (hypothermia, ↓GCS)
Differentials
- Sick euthyroid
- Central hypothyroidism
- Depression
Common mistakes
- Full-dose levothyroxine in elderly/CAD
- Not rechecking TSH at 6 wk
Disposition & follow-up
Levothyroxine, recheck TSH 6 wk; myxoedema → ICU.
Discharge package
MedicationsLevothyroxine (empty stomach)
Follow-upTSH at 6 wk then periodically
Warning symptomsPalpitations (over-replacement), worsening fatigue
💊 Treatment detail — doses & preparation
Levothyroxinethyroid replacement
Dose1.6 mcg/kg/day PO empty stomach, 30–60 min before food; start 25–50 mcg in elderly/CAD
Preparation25–300 mcg tablets; separate from Ca²⁺/iron/PPI by 4 h
MonitorTSH 6–8 wk after each change; keep same brand
Liothyronine (T3) IVmyxoedema coma
Dose5–20 mcg IV q8–12h (with hydrocortisone 100 mg q8h) or levothyroxine 200–400 mcg IV load
Preparation20 mcg ampoule slow IV push
MonitorHR, arrhythmia (start low in elderly/CAD); T4/T3 response
Hydrocortisone IVglucocorticoid
DoseAdrenal crisis: 100 mg IV bolus then 200 mg/24 h (50 mg q6h or infusion). Septic shock: 50 mg IV q6h
Preparation100 mg vial reconstitute with 2 mL water; bolus over 30 s–10 min
MonitorGlucose, Na⁺, BP response; taper when trigger resolves
📖 ATA HypothyroidismReviewed July 2026