Distribution of T4 TSH values in children--the Shifa experience.

OBJECTIVE To evaluate the distribution of Thyroxin (T4) and Thyroid Stimulating Hormone (TSH) values in children of various age groups attending our hospital. METHOD We have retrospectively reviewed the T4, TSH levels recorded at our hospital in children from birth to 5 years and evaluated the reference intervals for T4 TSH amongst different ages. Non parametric methods were used to establish a 97.5th, 95th, 50th, 5th and 2.5th centiles. RESULTS In T4 (n=1148) and TSH (n=1142) samples reviewed a TSH surge following delivery showed a sharp decline in the first 4 days of life. This was followed by a more gradual downward trend. Data on T4 estimations showed a similar but more gradual downward trend in advancing age groups. The 5th-95th centile reference range for TSH showed values between 1.7-22.5 (0-4 days; n=992), 0.6-13.3 (5-7 days; n=38), 0.9-14.0 (1 week-1 month; n=38), 0.5-13.6 (1 month-1 year, n=38) and 0.4-12.8 (1-5 years; n=38) microlU/mL. The 5th-95th centile reference range for T4 showed values between 10.7-25.0 (0-4 days; n=995), 6.5-20.4 (5-7 days; n=35), 8.0-18.1 (1 week-1 month; n=38), 6.0-16.1 (1 month-1 year; n=41), 6.9-15.3 (1-5 years; n=39) micro gm/dl. CONCLUSION We recommend using separate T4 and TSH reference values for children in different age groups. Further large-scale studies should be done in Pakistan to establish these reference values within age groups. A national center for neonatal thyroid screening is highly recommended.