In Reply.—Farriaux and Dhondt describe a centralized screening scribe gram for CH based on detection of elevated serum concentrations of TSH and suppression of TSH during treatment. I wish to note some merits and weaknesses of this approach vis-à-vis the primary T4-supplemental TSH measurement and treatment strategy described in our article.
With either strategy, some infants with CH will be missed. Primary TSH testing does not detect thyrotropin-releasing hormone or TSH deficiency, or late-onset TSH elevations.1 On the other hand, LaFranchi et al2 reported that, using a primary T4-supplemental TSH approach, approximately 10% of infants with primary hypothyroidism were not detected until a second screen was performed at 4 to 6 weeks of age. Virtually all of these infants had detectable thyroid tissue at the time of diagnosis, and half had low TSH concentrations on the first screening specimen that would not have been detected