treated with 7 micrograms per kilogram per day, a difference that was highly significant statistically.
Similar results have been reported by numerous other investigators. For example, Rovett, et al., have noted a 4 to 5 point increase in IQ of congenital hypothyroid infants when the dose of replacement was increased by as little as 1 to 2 micrograms per kilogram per day, from 7 to 9 micrograms per kilogram per day, to 8 to 10 micrograms per kilogram per day.
These data clearly show that congenital hypothyroidism is associated with significant irreversible cognitive impairment if treatment is inadequate. Relatively small differences in the dose of thyroxine replacement can have an enormous impact and irreversible impact, I might add, in the outcome of these babies. A potential difference of 33 percent in drug content is not acceptable for the optimal care of our patients. Bioequivalence should be determined by the serum TSH concentration, as you've already heard, which is a much more sensitive and physiologically meaningful assessment of bioequivalence than is the measure currently used to assess pharmacological equivalence.