From the Research
High reverse T3 (rT3) with normal TSH, free T4, and free T3 typically indicates non-thyroidal illness syndrome (NTIS), also known as euthyroid sick syndrome, as suggested by the most recent study 1. This pattern suggests that while the thyroid gland itself is functioning normally, the body is converting more T4 to reverse T3 instead of active T3 due to physiological stress. Common causes of elevated rT3 include:
- Severe illness
- Malnutrition
- Chronic inflammation
- Prolonged fasting
- Excessive exercise
- Psychological stress
- Certain medications like beta-blockers, steroids, and amiodarone No specific treatment for elevated rT3 alone is typically recommended if other thyroid values are normal, as supported by the study 2. Instead, addressing the underlying cause of physiological stress is the primary approach. The body increases rT3 production as a protective mechanism during times of stress or illness to conserve energy by reducing metabolic rate. If symptoms like fatigue, weight changes, or cold intolerance persist, further evaluation may be warranted, including testing for:
- Adrenal function
- Nutritional deficiencies
- Chronic inflammatory conditions It is essential to note that reverse T3 does not reliably differentiate hypothyroid sick syndrome from euthyroid sick syndrome, as shown in the study 2. Therefore, a comprehensive approach to diagnosis and treatment is necessary, taking into account the patient's overall clinical presentation and laboratory results, as discussed in the study 1.