Serum Concentration of Free T3, Free T4, and TSH In Healthy Children

Objective: It is rare that manufacturers report age-related FT 3 , FT 4 and TSH normal ranges in healthy children. Study design: Using a solid phase time-resolved fluoroimmunometric method, we determined serum FT 3 , FT 4 and TSH in 3,360 healthy children, age 2-16 years, that we grouped into two age ranges (2-7 yr and 9-16 yr). Results: Boys' and girls' mean serum thyroid hormone values substantially overlap in all age groups. In the age range 2-7 yr, FT 3 , FT 4 and TSH values were 0.10-0.67 ng/dl (mean 0.37 ng/dl), range 0.45-2.29 ng/dl (mean 1.18 ng/dl) and 0.10-5.9 μU/ml (mean 2.2 pU/ml), respectively. In the age range 9-16 yr, FT 3 , FT 4 and TSH values were 0.11-0.53 ng/dl (mean 0.35 ng/dl), 0.69-1.69 ng/dl (mean 1.07 ng/dl) and 0.20-6.1 pU/ml (mean 2.3 μU/ml), respectively. Conclusion: Our results represent a useful set of reference values in children and can help physicians in the management of thyroid diseases.