hypothyroidism indicated in the bottom panel as compared with the control group of normal children in the upper panel. An IQ of less than 85 is considered to be consistent with significant cognitive impairment, and as you can see, a majority of babies with congenital hypothyroidism had an IQ less than 85 indicated by the red arrow, but few of the normal babies had an IQ of 85 or less.
The third slide demonstrates the striking improvement and in fact the normalization of IQ in babies with congenital hypothyroidism indicated by the dark bars as compared with control patients when the diagnosis was made by newborn screening and treatment was early and adequate. Unfortunately, the IQ was only normal if treatment is adequate and even small decreases in the dose of thyroxine replacement are associated with a significantly reduced prognosis.
The next slide demonstrates a study in which the IQ of babies treated with two different starting doses was compared. It could be seen that babies treated with a higher dose, 10 micrograms per kilogram per day, had a mean IQ that was 21 points higher than that of babies