From the Guidelines
Myxedema is a severe form of hypothyroidism that requires immediate treatment with thyroid hormone replacement, typically with levothyroxine (T4) at an initial dose of 1.6 mcg/kg/day orally, as recommended by the US Preventive Services Task Force 1. The treatment of myxedema involves oral T4 monotherapy (levothyroxine sodium) as the principal treatment for hypothyroidism.
- The initial dose of levothyroxine is typically 1.6 mcg/kg/day orally, but for elderly patients or those with cardiac disease, a lower dose of 25-50 mcg/day is recommended, with gradual increases every 2-4 weeks based on TSH levels 1.
- In myxedema coma, a life-threatening emergency, intravenous levothyroxine (300-500 mcg initially, then 50-100 mcg daily) is necessary, along with supportive care including temperature management, fluid replacement, and respiratory support 1.
- Regular monitoring of thyroid function tests is required to adjust dosing, with a target TSH of 0.5-2.5 mIU/L, and patients should take levothyroxine on an empty stomach, 30-60 minutes before breakfast, and avoid taking it with calcium, iron supplements, or certain medications that can interfere with absorption 1. Myxedema develops due to prolonged, severe thyroid hormone deficiency, which slows metabolism and leads to accumulation of glycosaminoglycans in tissues, causing the characteristic swelling and other symptoms like fatigue, cold intolerance, and bradycardia.
- The USPSTF found no direct evidence on the benefits and harms of screening for thyroid dysfunction in nonpregnant, asymptomatic adults, and therefore considered the indirect evidence on screening accuracy, benefits of early treatment, and harms 1.
- The serum TSH test is the primary screening test for thyroid dysfunction, and multiple tests should be done over a 3- to 6-month interval to confirm or rule out abnormal findings 1.
- Overdiagnosis is of concern because it leads to the psychological consequences of labeling and unnecessary treatment, and it is a fundamental harm that should be avoided in disease prevention and health promotion 1.
From the FDA Drug Label
Myxedema Recommended starting dosage is 5 mcg daily This may be increased by 5 to 10 mcg daily every 1 or 2 weeks. When 25 mcg daily is reached, dosage may be increased by 5 to 25 mcg every 1 or 2 weeks until a satisfactory therapeutic response is attained. Usual maintenance dose is 50 to 100 mcg daily The recommended starting dosage of liothyronine for myxedema is 5 mcg daily, with a gradual increase until a satisfactory therapeutic response is attained, and the usual maintenance dose is 50 to 100 mcg daily 2.
From the Research
Thyroid Myxedema Overview
- Myxedema coma is a rare endocrine emergency resulting from the decompensation of severe hypothyroidism, associated with a high mortality rate 3.
- It is characterized by deterioration of mental status, hypothermia, hypotension, hyponatremia, and hypoventilation 3, 4.
Diagnosis and Treatment
- Diagnosis of myxedema coma is based on clinical suspicion, especially in patients with hypothyroidism and in the presence of precipitating factors 5.
- Treatment options include intensive supportive care and management of the underlying thyroid hormone deficiency with levothyroxine and liothyronine 3, 5, 6.
- Intravenous levothyroxine (T4) is commonly recommended, while hydrocortisone should be administered until coexisting adrenal insufficiency is ruled out 4.
Treatment Approaches
- Combination therapy with levothyroxine (LT4) and liothyronine (LT3) has been used, but its effectiveness is still being studied 7.
- Oral levothyroxine may be an effective option in resource-limited settings where intravenous thyroid hormone replacement is not available 5.
- Intramuscular levothyroxine has been used as an alternative in cases of poor compliance with oral levothyroxine treatment 6.