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Evaluation of a three years' systematic screening for hypothyroidism in the newborn.

par Delange, François ;Lagasse, Raphaël ;Bourdoux, Pierre ;Branders, C;Pardou, Anne ;Sacre, Lydia ;Brauman, Henri ;Ermans, André Marie
Référence Acta paediatrica Belgica, 32, 2, page (113-121)
Publication Publié, 1979

Article révisé par les pairs

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Résumé :

We report the results of systematic screening for congenital hypothyroidism in 7067 newborns in the Obstetrical Departments of the St. Pierre and Brugmann Hospitals in Brussels during a 3-year period. Screening was performed on the 5th day of life by means of serum TSH measurement in all newborns and T 4 measurements in addition in 836 of them. Length and weight were lower in girls than in boys (p <0.001), but the differences for T 4, and TSH were at the limit of significance (p <0.05). Therefore, sex was not taken into account. There were direct correlations between length, weight, and T 4, and inverse correlations between length, weight and TSH. There was also an inverse correlation between T 4 and TSH (p <0.001). The distribution of TSH levels was distinctly skewed to the right. The cut off point for TSH was arbitrarily estimated first at ≥ 12 μU/ml, and later at ≥ 20 μU/ml. The distribution of T 4 was more symmetrical and the mean (± 1 SD) was 13.6 (± 3.4) μg/dl. The cut-off point for T 4 was estimated at 5 μg/dl. These levels were reached in 0.7% of the newborns for TSH and in 1.0% for T 4. The total recall rate was 0.95% (67 of 7067 newborns). In the 67 newborns controlled, congenital hypothyroidism was confirmed in 14 i.e. in about 1/500 newborns. Only one presented a classical form of premanent hypothyroidism due to a small ectopic thyroid. The other 13 demonstrated transient hypothyroidism with spontaneous recovery. In three newborns, hypothyroidism was iodine induced following amniofetography. In the 10 others, iodine overload was excluded and the cause remained unknown. The syndrome occurred essentially in prematures with a variety of serious postnatal problems. In the 14 newborns with congenital hypothyroidism, the ratio of false negatives at the time of screening was 1/14 for TSH and 4/7 for T 4. In conclusion: TSH is more discriminative than T 4 in the screening for congenital hypothyroidism; Low T 4 levels measured in low birthweight infants most probably reflect a reduction in the functional capacity of the thyroid and should not be standardized for birthweight; transient hypothyrodism of unknown origin occurred in about 1/700 newborns in our series.