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Functional Hypothyroidism

Meaning

Functional Hypothyroidism describes a clinical presentation where a patient exhibits classic symptoms of thyroid hormone deficiency—such as fatigue, weight gain, and cold intolerance—despite having laboratory thyroid panel results that fall within the broad conventional reference range. This condition suggests an issue with the function or effectiveness of the thyroid system at the tissue level, rather than overt gland failure. Clinicians often look for subtle imbalances, including elevated Reverse T3 or impaired T4 to T3 conversion, which may not be flagged by standard screening tests. This nuanced diagnosis requires a sophisticated interpretation of the entire thyroid axis.