| Abstract: | A direct measurement of free thyroxine (FT4) by a radio-immunologic method using an analogue of thyroxine as tracer allowed to establish the normal values in 341 children from birth to puberty. These values were used as reference for the determination of free T4 in the diagnosis and management of treatment for congenital hypothyroidism. In 44 treated hypothyroid children, there was a positive correlation between the serum concentration of free T4 and the amount of levothyroxine given daily (r = 0.46, p less than 0.01). There was also a negative correlation between free T4 and serum TSH (r = 0.59, p less than 0.001). Thus, the measurement of free thyroxine seems to be a more reliable, more accurate and more sensitive parameter than that of total thyroxine or TSH for controlling the treatment of congenital hypothyroidism. |
