What are the diagnosis criteria for myxedema (hypothyroidism) coma?

From the Guidelines

Myxedema is diagnosed based on clinical features and laboratory findings indicating severe hypothyroidism, with diagnostic criteria including significantly elevated TSH levels and low free T4 levels, accompanied by characteristic clinical manifestations such as profound lethargy, hypothermia, bradycardia, and altered mental status. The diagnostic workup and evaluation for thyroid myxedema involve checking TSH, with the option of also including FT4, every 4-6 weeks as part of routine clinical monitoring for asymptomatic patients on immune checkpoint inhibitor (ICPi) therapy 1. For symptomatic patients, TSH and FT4 should be used for case detection.

Key Diagnostic Criteria

• Significantly elevated TSH levels (typically >10 mIU/L)
• Low free T4 levels
• Characteristic clinical manifestations, including:
  • Profound lethargy
  • Hypothermia (temperature <35°C)
  • Bradycardia
  • Hypotension
  • Hypoventilation
  • Altered mental status ranging from confusion to coma
  • Non-pitting edema particularly in the face, hands, and pretibial areas

Management

According to the guidelines, patients with severe symptoms, medically significant or life-threatening consequences, or unable to perform activities of daily living (ADL) should have ICPi held until symptoms resolve to baseline with appropriate supplementation 1. Endocrine consultation is recommended to assist with rapid hormone replacement, and hospital admission is necessary for developing myxedema, with inpatient endocrinology consultation to assist with IV levothyroxine dosing, steroids, and supportive care.

Treatment

Treatment for myxedema coma, a life-threatening emergency, requires admission and a high level of care, with thyroid supplementation and reassessment as indicated 1. Hydrocortisone should be given before thyroid hormone is initiated if there is uncertainty about whether primary or central hypothyroidism is present.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Thyroid Myxedema Diagnosis Criteria

The diagnosis of thyroid myxedema is based on a combination of clinical and laboratory findings. Some of the key criteria include:

• Characteristic symptoms such as weakness, cold intolerance, mental and physical slowness, dry skin, typical facies, and hoarse voice 2
• Results of total serum thyroxine and free thyroxine index tests to confirm the diagnosis 2
• Blood levels of thyroid-stimulating hormone and free thyroxine to suggest thyroid dysfunction 3
• Clinical presentation of myxedema, which can represent a valuable symptom in establishing the correct diagnosis, even in subclinical cases of thyroid diseases 4

Laboratory Tests

Laboratory tests play a crucial role in the diagnosis of thyroid myxedema. These tests include:

• Total serum thyroxine and free thyroxine index tests 2
• Thyroid-stimulating hormone and free thyroxine levels 3
• Thyrotropin and free T4 and free triiodothyronine (FT3) levels to diagnose subclinical hypothyroidism 5

Clinical Evaluation

Clinical evaluation is essential in patients with disparate clinical and laboratory findings. This includes:

• Careful attention to nonspecific complaints, myxedematous changes, and signs of dysfunction of any organ system, especially in older female patients 6
• Recognition of myxedema coma, which is potentially fatal and must be recognized and treated emergently, usually prior to laboratory confirmation 6