1. Delay in the relaxation phase of reflexes, dry skin, a husky voice, loss of the outer part of the eyebrows, and weight gain. In severe disease there is lethargy, bradycardia, hypothermia, and respiratory depression. Deposition of a mucinous substance causes thickening of the subcutaneous tissues producing a nonpitting oedema. Myxoedematous infiltration of the vocal cords and tongue can occur. Cardiovascular complications include ischaemic heart disease, bradycardia, pericardial effusion, and cardiac failure (Gomberg-Maitland & Frishman 1998). Neurological complications may involve carpal tunnel syndrome, polyneuritis, myopathy, and cerebellar syndrome.About 70% of patients have paraesthesia or sensory neuropathy. Psychiatric disturbances may predominate.
2. An increased TSH, and decreased T4 and sometimes T3. It should be remembered that depression ofT4 alone often occurs in ill patients who are not hypothyroid. Acute hypothyroidism has been been described in a severely ill surgical patient (Mogensen & Hjortso 1988).
3. Hypothyroidism is associated with bradycardia and AV conduction blocks. Diastolic hypertension may occur and is associated with increased systemic resistance (Gammage & Franklyn 1997).Ventricular systolic and diastolic function are impaired.The ECG is of low voltage with flattened or inverted T waves, and CXR may show mild cardiac enlargement.
4. Features of myxoedema coma include anaemia, which may be microcytic or macrocytic, lactic and respiratory acidosis, inappropriate ADH secretion, with severe hyponatraemia (Hanna & Scanlon 1997), and hypoglycaemia.
5. Hyperlipidaemia, with increases in total and low-density cholesterol.
6. Associated diseases include diabetes mellitus, pernicious anaemia, and Addison's disease.
7. Patients occasionally develop hypothyroidism during pregnancy and this is associated with thyroid antibodies, preeclampsia, preterm delivery, and subsequent impairment of IQ of the child (Montoro 1997, Haddow et al 1999).
8. Most cases are iatrogenic and follow radioactive iodine or thyroidectomy, but amiodarone and lithium are other causes.
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