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Newborn Screening for Congenital Hypothyroidism in Japan
1Department of Pediatrics, Teikyo University Chiba Medical Center, Chiba 299-0111, Japan.
Insights
Congenital hypothyroidism (CH) screening in Japan has evolved, with incidence doubling to 1:2500. This rise is linked to lower screening thresholds and increased screening for premature infants.
Area of Science:
- Endocrinology
- Pediatrics
- Public Health
Background:
- Congenital hypothyroidism (CH) is a leading preventable cause of intellectual disability.
- Newborn screening programs are crucial for early detection and treatment of CH.
- Japan has implemented and revised CH screening guidelines since 1979.
Purpose of the Study:
- To review the evolution and current status of newborn screening for CH in Japan.
- To analyze factors contributing to the increasing incidence of CH.
- To highlight strategies for managing CH in at-risk infant populations.
Main Methods:
- Analysis of historical data on CH screening programs in Japan.
- Review of clinical guidelines and screening strategies for CH.
- Examination of incidence trends and contributing factors, including screening cutoffs and infant demographics.
Main Results:
- The incidence of CH in Japan has doubled to approximately 1:2500.
- Lowered TSH screening cutoffs have increased detection of mildly affected cases.
- Rescreening protocols for premature and low birth weight infants have been implemented.
Conclusions:
- CH screening in Japan has improved early detection and treatment.
- The increasing incidence reflects both improved detection and potentially a true rise in CH cases.
- Continued refinement of screening protocols is essential for optimal CH management.
Abstract:
Congenital hypothyroidism (CH) is the most common preventable cause of intellectual impairment or failure to thrive by early identification and treatment. In Japan, newborn screening programs for CH were introduced in 1979, and the clinical guidelines for newborn screening of CH were developed in 1998, revised in 2014, and are currently undergoing further revision. Newborn screening strategies are designed to detect the elevated levels of thyroid stimulating hormone (TSH) in most areas of Japan, although TSH and free thyroxine (FT4) are often measured simultaneously in some areas. Since 1987, in order not to observe the delayed rise in TSH, additional rescreening of premature neonates and low birth weight infants (<2000 g) at four weeks of life or when their body weight reaches 2500 g has been recommended, despite a normal initial newborn screening. Recently, the actual incidence of CH has doubled to approximately 1:2500 in Japan as in other countries. This increasing incidence is speculated to be mainly due to an increase in the number of mildly affected patients detected by the generalized lowering of TSH screening cutoffs and an increase in the number of preterm or low birth weight neonates at a higher risk of having CH than term infants.
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