Hormone Health Hub: Expert Insights on Testing, Balance & Better Living — total T4 testing

Many patients produce sufficient thyroid hormone yet still suffer from classic hypothyroid symptoms. Why? Because standard TSH testing misses the full picture. In this clinical guide, Jim Paoletti explains the functional approach to thyroid assessment — examining T4 production, TBG binding, T4-to-T3 conversion, cortisol interference, ferritin and vitamin D — and outlines exactly which tests are needed for a complete analysis.

Normal thyroid blood tests don’t always explain why patients still suffer from fatigue, cold intolerance, brain fog and weight gain. In this in-depth clinical article, ZRT Laboratory explains the critical role of selenium in thyroid hormone synthesis and T4-to-T3 conversion, how heavy metals like mercury and arsenic sequester selenium and inactivate protective antioxidant enzymes, and why this can trigger Hashimoto’s thyroiditis — even when TSH, T4 and T3 appear normal.