Iodine deficiency disorders incidence in neonates based on the experience with mass screening for congenital hypothyroidism in southeast Poland in the years 1985-2000.

Thyroid hormones are very important for the child mental and physical development. In southeast Poland screening for congenital hypothyroidism detection was established in 1985; this region was defined as an iodine deficient area. The results provided the first signal pointing to insufficient iodine prophylaxis in the region. In the years 1985-2000, a total of 634,179 newborns were tested. TSH levels in blood spots on filter paper were determined using three consecutive methods: RIA, fluoroimmunometry (FIA) and luminoimmunemetry (LIA). In the first five years of the program, the incidence of permanent hypothyroidism was 1:4,000, while the incidence of iodine deficiency disorders (IDD) was 1:272. These findings led to the recognition of the fact that iodine prophylaxis had been discontinued in 1981 and reintroduced in 1992 and from that time on the incidence of IDD in neonates has been evidently lower. In the period between 1991 and 2000, we observed a 0.14% incidence rate of IDD, while until 1991 it had been 0.5%. In the years 1998-2000, the respective value was 1:5,420. The incidence of transient hypothyroidism also dropped from 1:3,920 to 1:48,474. Therefore we conclude that, based on screening studies carried out since 1985, the analysis of TSH levels may be regarded as a tool for iodine deficiency monitoring in neonates. Between 1985-2000, a drop in the incidence of IDD in newborns is clearly seen. Moreover, investigations carried out in particular years show that even low-grade iodine supplementation leads to TSH level decrease in newborns.