Myxoedema

Define:

  • Severe hypothyroidism characterized by 1) decrease mental status 2) hypothermia

Why should I know?

  • endocrine emergency which remains a clinical diagnosis
  • mortality rate 30-40%
  • treat based on suspicion without delay for laboratory confirmation.

Presentation:

  • CNS: confusion, lethargy, psychosis (myxoedema madness), seizures, slow ankle reflexes.
  • Hypothermia: impaired thermogenesis
  • Hyponatremia: renal impairment, SIADH
    • renal impairment: hypothyroidism cause increase peripheral vascular resistance and reduce GFR, reduce water excretion, cause dilution hyponatremia. proposed
    • SIADH: hypothyroidism cause decrease cardiac output and  hypovolemia then lead to baroreceptor-mediated  ADH release. debating
  • Hypoventilation with respiratory acidosis, due to depression of central ventilatory drive.
  • Hypoglycemia: due to decrease gluconeogenesis and associated adrenal insufficiency.
  • CVS: bradycardia, heart failure (elevated jugular venous pressure, pedal edema, S3), pericardial effusion (muffled heart sound), hypotension.
  • Weight gain
  • Voice change
  • Skin: puffy face, carotinemia
  • thyroidectomy scar
  • sepsis

Related image

figure: carotinemia

Causes:

Precipitating factors:

  • infection
  • trauma
  • Acute myocardial infarction
  • Cold exposure
  • sedative drug; opiates & BZD
  • Stroke

Long standing hypothyroidism:

  • surgery or radio iodine therapy
  • medication: amiodarone, lithium
  • autoimmune thyroiditis

Investigation:

  • DXT
  • FBC
  • RP -hyponatremia
  • CK – >1000iu/L -hypothyroid cause myopathy
  • ABG: type 2 failure cause by hypoventilation
  • TFT
  • Serum cortisol: look for associated hypocortisolism
  • CXR: cardiomegaly, pleural effusion, pulmonary edema, penumonia
  • ECG: MI, bradycardia, J waves (hypothermia), low voltage QRS complexes (in pericardial effussion)Image result for j waves ecg

Figure: J waves: causes of J waves ; Hypothermia, Brugada Syndrome, BER, Hypercalcemia

 

Management

  • ABCD
  • Fluid resuscitation if hypotension. add vasopressor if not respond to fluids. avoid hypotonic fluid in hyponatremia.
  • rewarm passively, with blanket.
  • IV Hydrocortisone 100mh TDS (associated hypocortisolism, stop if serum cortisol normal).
  • Hypoglycemia, treat with IVD D10%
  • Hyponatremia, correct slowly with normal saline
  • Cardiac failure: diuretics, vasodilator
  • Sepsis: Antibiotic
  • Thyroid hormone replacement theraphy
    • IV or oral
    • T3 (triiodothyronine- advantage: rapid onset, greater biological activity) or T4 (L-thyroxine)
    • T3: 2.5 ug TDS, double dose every 2-3 days, target 30-40 ug/day
    • T4: 25 ug as test dose, then increase to 500 ug/day on 1st day. subsequent dose 25-100 ug/day.
    • maintenance dose should be lower in elderly and ischemic heart disease.
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