Fetal hypothyroidism: I. Effects of hypothyroidism on neural development; II. Fetal versus maternal contributions to fetal thyroxine requirements; III. clinical implications

摘要

In the 1960s, congenital hypothyroidism was the major cause of preventable intellectual disability. Early treatment is essential to prevent progressive neurological deficit but congenital hypothyroidism is infrequent (1 in 2500-3000 births), and affected infants show few obvious signs of hypothyroidism. Thus, treatment was often delayed for weeks or months. Approximately one-half of the infants with congenital hypothyroidism treated before age 6 months attained an IQ in the low or low-normal range, whereas those not treated until after age 6 months usually suffered severe mental impairment. The invention of radioimmunoassay in 1959-1960 by Berson and Yalow and advances in molecular and cellular biology and hormone physiology in the 1970s and 1980s facilitated the development of sensitive and specific assays for thyroid and pituitary hormones and the characterization of maternal and fetal thyroid hormone metabolism and the effects of thyroid hormones on brain maturation.