Endocrine Abstracts

Thyroid hormone (TH) is essential for brain development in utero and during the first two to three years of life. The negative effects of TH deficiency on brain development are irreversible. Early detection of TH deficiency in neonates (congenital hypothyroidism (CH) through newborn screening (NBS)) allows for early treatment, thereby preventing brain damage. Research in the 19th century highlighted the importance of early detection and treatment of CH to prevent growth and mental development issues. Newborn screening began in Buffalo, New York, in 1960 with Dr. Robert Guthrie’s blood test for PKU. By the 1970s, the thyroid gland’s production of thyroxine (T4) and triiodothyronine (T3) was known, and radioimmunoassay enabled detection of thyroid hormone deficiencies. Screening for CH began in 1973 with the measurement of total T4 in dried blood spots. In 1982, an international conference on neonatal thyroid screening with representatives from 34 countries led to widespread screening. Annually, 7-9 million newborns are screened in industrialized countries. Primary CH affects about 1 in 3800 to 1 in 4000 newborns, mainly due to thyroid dysgenesis (90%). The conference recommended focusing on detecting increased TSH levels and screening premature infants due to often low T4 levels. Currently, worldwide, the majority of NBS programs for CH employ TSH as the primary screening marker although a select few programs still utilize T4 as the primary marker, enabling the detection of both primary and central CH. However, neonatal screening for CH remains challenging, with continuous efforts to improve algorithms by adapting testing protocols, and using reference intervals for screening parameters. New developments, such as machine learning, and DNA-based screening, are being explored to enhance screening performance and reduce the number of false positive referrals. This presentation provides an overview of the aspects of the screening on CH from the start of screening to the present.