Free Triiodothyronine (FT3)

You're absolutely right. Estimating Free Triiodothyronine (FT3) and Free Thyroxine (FT4) levels is crucial in accurately diagnosing thyroid dysfunctions. FT3 and FT4 are the unbound, biologically active forms of the hormones, making them more reflective of the thyroid's actual hormonal activity. 

While Total T3 and Total T4 levels include both bound and unbound hormones, their concentrations can be influenced by factors like protein levels in the blood, which can vary due to non-thyroidal illnesses, pregnancy, or medication use. This can sometimes lead to misleading results if healthcare providers only rely on T3 and T4 levels.

By measuring FT3 and FT4, doctors can better assess thyroid function, especially in cases where Total T3 and T4 levels may not align with clinical symptoms. This enhances the sensitivity and specificity of diagnosing conditions such as hyperthyroidism, hypothyroidism, and other thyroid-related disorders. Consequently, more accurate diagnosis leads to better-targeted treatment plans for patients.