A study of thyroid hormone in children and adolescents in a series of MZ and DZ twins and their siblings.

Abstract

Stabenau and Pollin (1968) observed, in a study of 23 pairs of adult MZ twins, that a significant correlation existed between birth-weight (a measure of fetal maturity) and adult protein-bound iodine (PBI) (r = + 0.58, P < 0.001). In a sub-sample of 12 individuals, the correlation between birthweight and thyroxine-binding globulin (TBG) was + 0.94 (P < 0.001). These data suggested that differences in protein hormonal binding may be established as a result of intrauterine factors, the effect of which may persist into adulthood. The study of neonates has demonstrated that measures of PBI and butanol-extractable iodine (BEI) are higher at birth than in later adulthood, and that rapid changes in individual values occur during the early neonatal period. Marks and Man (1965), Perry et al (1965) and Man (1966) have demonstrated that BEI and PBI values are higher for infants who are heavier in weight at birth and lower for infants of low birthweight. The weight of a fetus at birth has been used as one single estimate of fetal maturity when measures such as fetal length and gestational age are unavailable.A sample of children and adolescent MZ and DZ twins and singletons was studied to test the hypothesis that measures of thyroid hormone activity are related to maturity at birth. In addition, estimates of the relative genetic control for thyroid hormone levels were made.