- Published on
Emergency And Acute Medicine – Hypothyroidism
Basics
Description Decreased effective circulating thyroid hormone causes reduced metabolic rate and diminished catecholamine sensitivity. More common in women and the elderly. Myxedema coma is a rare, life-threatening decompensation marked by altered mental status and impaired thermoregulation precipitated by stress in a hypothyroid patient.
Etiology
Primary causes include idiopathic, congenital, autoimmune thyroiditis (Hashimoto disease), iodine deficiency (most common worldwide), neoplasm, infection, and iatrogenic causes (thyroid surgery, radioiodine, external radiation). Drug induced causes include iodides, lithium, amiodarone, sunitinib, bexarotene, interferons, narcotics, and sedatives. Central hypothyroidism is rare and due to pituitary or hypothalamic dysfunction, often with other hormone deficiencies.
Myxedema coma is triggered by infection, hypothermia, intoxication, drugs, stroke, heart failure, trauma, or pregnancy.
Diagnosis
Signs And Symptoms
History: Fatigue, cold intolerance, weight gain, constipation, depression, cognitive slowing, headaches, myalgias, muscle weakness, menorrhagia, infertility, carpal tunnel syndrome.
Physical exam: Periorbital edema, coarse sparse hair, brittle nails, loss of lateral third of eyebrows, hoarse voice, goiter, dry pale cool skin, nonpitting edema, prolonged relaxation of deep tendon reflexes.
Myxedema coma: Altered mental status, hypothermia, hypotension, bradycardia, respiratory failure.
Pediatric And Geriatric Considerations
Congenital hypothyroidism largely prevented by newborn screening. Childhood disease usually due to Hashimoto thyroiditis and may impair growth and development. Elderly patients may present atypically, mimicking normal aging.
Essential Workup
Laboratory confirmation may not be immediately available; treatment should be initiated based on clinical suspicion in severe cases.
Diagnosis Tests And Interpretation
Labs: Low total and free T4 and T3. TSH elevated in primary hypothyroidism, normal or low in central causes. Associated findings include anemia, hyponatremia, hypoglycemia, hypoxemia, hypercapnia, respiratory acidosis, elevated CK, LDH, cholesterol, and creatinine.
Imaging: Chest radiograph may show cardiomegaly from pericardial effusion.
ECG: Sinus bradycardia, low voltage, PR prolongation, bundle branch blocks, QT prolongation, nonspecific ST–T changes; Osborn waves if profoundly hypothermic.
Differential Diagnosis
Chronic kidney disease, heart failure, depression, hypoalbuminemia, pernicious anemia, nephrotic syndrome, sepsis.
Alert Euthyroid sick syndrome may cause abnormal thyroid tests during acute illness.
Treatment
Initial Stabilization/Therapy ABCs with airway protection and ventilation as needed. Cardiac monitoring, oxygen supplementation, cautious passive rewarming. Avoid aggressive rewarming.
Emergency Department Treatment/Procedures
Mild hypothyroidism: Outpatient oral thyroid hormone replacement.
Myxedema coma: Medical emergency. Initiate IV thyroid hormone replacement immediately on suspicion. Use lower doses and avoid aggressive T3 in elderly or cardiac patients. Administer hydrocortisone to prevent adrenal crisis. Treat hypoglycemia with dextrose, hypotension with IV fluids (pressors often ineffective until thyroid hormone given), severe hyponatremia with hypertonic saline if indicated. Identify and treat precipitating cause.
Medication
First line thyroid hormone therapy:
• T4 IV load ~2 μg/kg (ideal body weight) then 10–40 μg IV or PO daily
• Optional T3 IV 10 μg load then 10 μg IV q8–12h (avoid in elderly/cardiac patients)
Second line/supportive: Hydrocortisone 100 mg IV q6–8h, dextrose IV for hypoglycemia.
Follow-Up And Disposition
Admission Criteria All patients with myxedema coma require ICU admission.
Discharge Criteria Uncomplicated hypothyroidism suitable for outpatient management.
Follow-Up Recommendations Primary care or endocrinology follow-up for long-term thyroid hormone management. Pregnant, elderly, and cardiac patients require cautious dose titration.
Key Points And Cautions
Symptoms are nonspecific and easily overlooked. Myxedema coma has high mortality and requires prompt treatment. Do not delay therapy awaiting lab confirmation. Avoid aggressive T3 use in elderly or patients with ischemic heart disease.
Basics
Description Decreased effective circulating thyroid hormone causes reduced metabolic rate and diminished catecholamine sensitivity. More common in women and the elderly. Myxedema coma is a rare, life-threatening decompensation marked by altered mental status and impaired thermoregulation precipitated by stress in a hypothyroid patient.
Etiology
Primary causes include idiopathic, congenital, autoimmune thyroiditis (Hashimoto disease), iodine deficiency (most common worldwide), neoplasm, infection, and iatrogenic causes (thyroid surgery, radioiodine, external radiation). Drug induced causes include iodides, lithium, amiodarone, sunitinib, bexarotene, interferons, narcotics, and sedatives. Central hypothyroidism is rare and due to pituitary or hypothalamic dysfunction, often with other hormone deficiencies.
Myxedema coma is triggered by infection, hypothermia, intoxication, drugs, stroke, heart failure, trauma, or pregnancy.
Diagnosis
Signs And Symptoms
History: Fatigue, cold intolerance, weight gain, constipation, depression, cognitive slowing, headaches, myalgias, muscle weakness, menorrhagia, infertility, carpal tunnel syndrome.
Physical exam: Periorbital edema, coarse sparse hair, brittle nails, loss of lateral third of eyebrows, hoarse voice, goiter, dry pale cool skin, nonpitting edema, prolonged relaxation of deep tendon reflexes.
Myxedema coma: Altered mental status, hypothermia, hypotension, bradycardia, respiratory failure.
Pediatric And Geriatric Considerations
Congenital hypothyroidism largely prevented by newborn screening. Childhood disease usually due to Hashimoto thyroiditis and may impair growth and development. Elderly patients may present atypically, mimicking normal aging.
Essential Workup
Laboratory confirmation may not be immediately available; treatment should be initiated based on clinical suspicion in severe cases.
Diagnosis Tests And Interpretation
Labs: Low total and free T4 and T3. TSH elevated in primary hypothyroidism, normal or low in central causes. Associated findings include anemia, hyponatremia, hypoglycemia, hypoxemia, hypercapnia, respiratory acidosis, elevated CK, LDH, cholesterol, and creatinine.
Imaging: Chest radiograph may show cardiomegaly from pericardial effusion.
ECG: Sinus bradycardia, low voltage, PR prolongation, bundle branch blocks, QT prolongation, nonspecific ST–T changes; Osborn waves if profoundly hypothermic.
Differential Diagnosis
Chronic kidney disease, heart failure, depression, hypoalbuminemia, pernicious anemia, nephrotic syndrome, sepsis.
Alert Euthyroid sick syndrome may cause abnormal thyroid tests during acute illness.
Treatment
Initial Stabilization/Therapy ABCs with airway protection and ventilation as needed. Cardiac monitoring, oxygen supplementation, cautious passive rewarming. Avoid aggressive rewarming.
Emergency Department Treatment/Procedures
Mild hypothyroidism: Outpatient oral thyroid hormone replacement.
Myxedema coma: Medical emergency. Initiate IV thyroid hormone replacement immediately on suspicion. Use lower doses and avoid aggressive T3 in elderly or cardiac patients. Administer hydrocortisone to prevent adrenal crisis. Treat hypoglycemia with dextrose, hypotension with IV fluids (pressors often ineffective until thyroid hormone given), severe hyponatremia with hypertonic saline if indicated. Identify and treat precipitating cause.
Medication
First line thyroid hormone therapy:
• T4 IV load ~2 μg/kg (ideal body weight) then 10–40 μg IV or PO daily
• Optional T3 IV 10 μg load then 10 μg IV q8–12h (avoid in elderly/cardiac patients)
Second line/supportive: Hydrocortisone 100 mg IV q6–8h, dextrose IV for hypoglycemia.
Follow-Up And Disposition
Admission Criteria All patients with myxedema coma require ICU admission.
Discharge Criteria Uncomplicated hypothyroidism suitable for outpatient management.
Follow-Up Recommendations Primary care or endocrinology follow-up for long-term thyroid hormone management. Pregnant, elderly, and cardiac patients require cautious dose titration.
Key Points And Cautions
Symptoms are nonspecific and easily overlooked. Myxedema coma has high mortality and requires prompt treatment. Do not delay therapy awaiting lab confirmation. Avoid aggressive T3 use in elderly or patients with ischemic heart disease.
0 Comments
