Thyroid Function Index Panel Calculator

TSH (mIU per L) Free T4 (ng per dL) Thyroid Function Index Panel Explanation and Clinical Context The Thyroid Function Index is an integrated measure that combines serum TSH and free T4 to provide a more stable and physiologically relevant indicator of thyroid status. TSH alone can fluctuate because of pituitary dynamics and non thyroidal influences while free T4 may remain within reference intervals in early thyroid dysfunction. The Thyroid Function Index improves interpretability by using a logarithmic transformation of TSH and proportional weighting of free T4 which reflects the sensitivity of the hypothalamic pituitary thyroid axis.

Normal thyroid function generally produces a moderately centered index while a lower index suggests increasing thyroid hormone effect consistent with a hyperthyroid pattern and a higher index indicates reduced thyroid hormone effect consistent with a hypothyroid pattern. The tool is useful for clinicians who require a synthesized representation of thyroid physiology for monitoring treatment adjustment evaluation of atypical thyroid profiles and interpretation of borderline laboratory values. Reference Lacout C et al.

Thyroid Function Index A composite measure using TSH and free thyroxine enhances classification of thyroid status. Clin Chem Lab Med. 2015.

DOI 10.1515