ESPE Abstracts

Background and aims. In several European countries, the incidence of primary congenital hypothyroidism (PCH) seems to increase in the last decade, especially in countries that have lowered the newborn screening TSH cutoff. In Flanders, two centers manage since 2012 the newborn screening for PCH and these maintained the same TSH assay (Delphia, Perkin Elmer) and cutoff (15 mU/l). We studied the current incidence and etiology of PCH and initiation of thyroxine treatment in Flanders.

Methods. Birth data, results of hormonal measurements at screening and at recall, scintigraphy and ultrasound results at initial evaluation, and data on thyroxine treatment initiation were analyzed from newborns diagnosed with PCH screened between 2012 and 2017 in a single center (VCBMA), covering about half of the newborns in Flanders.

Results. During the study period, 167,653 live newborns were screened for CH, and thyroxine treatment was started in 40 (22 females [F] and 18 males [M]) newborns because of confirmed PCH (serum TSH > 20 mU/l at recall). The yearly number of treated newborns varied greatly (between 3 and 15 per year), but without a clear increase. A low serum FT4 (< 15 pmol/l) was present in 36 newborns. Median (range) gestation, birthweight SDS and length SDS were 40 (25-42) weeks, 0.00(-2.31-2.57) and -0.14(-1.93-2.89). Based on scintigraphy (n = 29) and/or ultrasound (n = 32), a diagnosis of gland in situ, ectopy, aplasia and hypoplasia and no imaging was made in respectively 12 (5F), 15 (11 F), 10 (5 F) and 2 (0 F) and 1 (0 F) newborns. Thyroxine was started at a median (range) age of 10 (3-18) days (n = 35 before day 14). The thyroxine starting dose ranged between 25 (n =6) and 50 µg (n = 10). Newborns with apparent aplasia had the lowest FT4 concentrations (median (range) 3 (0.4-18) pmol/l) and received the highest starting dose (12.6 (7.6-20.4) µg/kg/day) when compared with the other etiologies. One infant had a congenital heart disease and one had trisomy 21.

Conclusion. The overall incidence of PCH was 1 in 4191 live newborns. Abnormalities in thyroid morphogenesis were diagnosed in 69 %. No fetal growth differences were seen between the different etiologies, but a female gender excess was observed in the newborns with ectopy. Newborns with apparent thyroid aplasia received the highest dose. Thyroxine treatment was initiated before the age of 14 days in 87.5 % of the newborns.