INCREASED INCIDENCE OF CONGENITAL-MALFORMATIONS IN CHILDREN WITH TRANSIENT THYROID-STIMULATING HORMONE ELEVATION ON NEONATAL SCREENING

We investigated the incidence of congenital malformation in all infant s with raised thyroid-stimulating hormone (TSH) levels on neonatal scr eening in Scotland between August 1979 and December 1993. Of 544 infan ts with elevated TSH, 31 (9%) had one or more malformations: 12 cardia c, 15 noncardiac, and 16 dysmorphic syndromes (including 5 with Down s yndrome). Criteria were devised to distinguish between definite or pro bable congenital hypothyroidism and transient TSH elevation. Congenita l hypothyroidism was considered definite in 224 (65.1%) infants and pr obable in 11 (3.2%). Eighty-eight (25.6%) infants had transient TSH el evation, whereas thyroid status was uncertain in 21 (6.1%). In the def inite group 12 (5.4%) infants had one or more malformations compared w ith 13 (14.8%) in the transient group. Cardiac malformation, noncardia c malformation, dysmorphic syndromes, and ''sickness'' were much more frequent in the transient compared with the definite group: 5.7% versu s 1.8%, 8.0% versus 1.8%, 6.8% versus 2.7%, and 37.5% versus 7.1%, res pectively. The incidence of congenital malformation in bona fide conge nital hypothyroidism is lower than has been previously reported. The h igh incidence of congenital malformation associated with transient TSH elevation indicates the need to reevaluate the diagnosis of hypothyro idism in all infants with TSH elevation and concurrent illness or malf ormation.