Raana Abbas, Hafiz Ghulam Abbas, Abubaker Shahid, Sohail Chand, Sara Nawaz.
Reference Intervals for Free T3 and Free T4 in Pakistani Euthyroid Patients: Effect of Age and Gender on Thyroid Function.
J Coll Physicians Surg Pak Jan ;24(11):806-9.

Objective: To establish reference intervals for Free Triiodothyronine (FT3) and Free Thyroxine (FT4) in euthyroid subjects and to assess the effect of age and gender on FT3 and FT4. Study Design: Cross-sectional, analytical study. Place and Duration of Study: Institute of Nuclear Medicine and Oncology (INMOL), Lahore, from January 2009 to April 2011. Methodology: FT3 and FT4 were measured in 852 euthyroid patients. Those with previous thyroid surgery, on thyroid-related medication and severe non-thyroid illness were excluded. Results: There were 215 males and 637 females with mean age of 46 years. The reference intervals, revealed by this study, for FT3 and FT4 were 2.80 - 5.39 pmol/L and 11.9 - 22.2 pmol/L respectively. The mean difference between gender groups and age groups was found statistically significant for FT3 (gender: p < 0.001; age: p < 0.001) but statistically insignificant for FT4 (gender: p=0.147; age: p=0.201). Conclusion: There was no effect of gender and age on FT3 and FT4. The age with serum FT3 and FT4 significantly negatively correlated but this correlation was stronger for FT3 as compared to FT4 levels. Reference intervals of FT3 and FT4 for male (2.99 - 5.63 pmol/L, 12.3 - 22.6 pmol/L) and female (2.77 - 5.29 pmol/L, 11.7 - 22.1 pmol/L) respectively are suggested.

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