[The surface of epiphyses of the knee: index of the duration of neonatal hypothyroidism].

The surfaces of the epiphyses of the knees were calculated in 34 neonates with hypothyroidism detected with a systematic screening and in 32 normal neonates. In the group of neonates with hypothyroidism, the surface of the lower femoral point was 12.7 +/- 0.9 mm2 and that of the upper tibial point 1.8 +/- 0.9 mm2. There was a significant difference (P less than 0.01) for both epiphyses between children of the 2 groups. The use of mathematical formula excluding non specific factors showed significant correlation between the corrected values for lower femoral points, and T4 and T3 plasma levels. These corrected values were higher in neonates with thyroid ectopia than in neonates with thyroid aplasia. There was also a significant correlation between the corrected values for lower femoral points and the IQ at 6 months and 2 years. Thus, the calculation of the surface of the epiphyses of the knee may be considered as a criterion of duration and severity o hypothyroidism and may be an index for the determination of the ante- or post-natal onset of the disease.