Blood serum triiodothyronine (T3), thyroxine (T4) and thyroid stimulating hormone (TSH) concentrations in healthy children at the age of 1 and 2 years.

The physiological mean concentrations of T3, T4 an TSH in 150 healthy children aged from 1 month to 2 years of life decreased gradually with age. The statistically significant difference was observed only in T3 levels between the first and second year of life. The remaining parameters did not show statistically significant differences.