Objective-To report the experience, obstacles, and strategies of screening
for congenital hypothyroidism.
Setting-Newborns in Mexico.
Methods-Thyroid stimulating hormone (TSH) was measured by enzyme immunoassa
y using commercial kits in 1 140 364 newborns.
Results-There were 464 positive cases, of whom 299 (64.4%) were girls. 236
(50.9%) showed ectopic nodules, 202 (43.5%) thyroid agenesis, 21 (4.5%) dys
hormonogenesis, and 5 (1.1%) an unclassified goitre. The false positive rat
e was 0.024% and there were 11 false negative results. Currently, 600 000 (
26%) of the 2 300 000 newborns are screened. This percentage has been incre
ased in recent years by taking samples from cord blood and will be increase
d further by starting congenital hypothyroidism screening at social securit
y units and by midwives screening infants born at home.
Conclusions Mental retardation in infants in developing countries can be re
duced by neonatal screening, and carefully planned strategies can steadily
extend the benefits of screening.