Farriaux and Dhondt suggest that US may be just as sensitive as radionuclide scanning to help determine the cause of CH in children. They were able to detect 73% of ectopic glands while we could not detect any. The reasons for this are not clear but may relate to the sensitivity of the equipment or the fact that they scanned their patients at 4 months of age, whereas ours were examined at birth. The results in athyrotic children and in those with NLGs were similar to ours. We do not dispute their results but agree that US has the limitations that they indicate. We do not believe that the level of serum thyroglobulin is helpful. With further technical advances, US may replace radionuclide scanning. However, at the present time, we believe that radionuclide scanning remains the "gold standard" for diagnosing the cause of CH.