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Thyroxine-binding globulin, triiodothyronine, thyroxine and thyrotropin in newborn infants and children
Insights
Maternal thyroxine-binding globulin (TBG) levels are higher than in newborns. TBG remains elevated in children compared to adults, independent of postnatal T3, T4, and TSH changes.
Area of Science:
- Endocrinology
- Neonatal Physiology
- Pediatric Metabolism
Background:
- Thyroid hormones, including thyroxine (T4) and triiodothyronine (T3), are crucial for development.
- Thyroxine-binding globulin (TBG) influences thyroid hormone availability.
- Thyrotropin (TSH) regulates thyroid hormone production.
Purpose of the Study:
- To quantify TBG, T3, T4, and TSH levels in newborns and children.
- To compare pediatric TBG levels with maternal and adult controls.
- To investigate the relationship between TBG and other thyroid hormones postnatally.
Main Methods:
- Radioimmunoassay (RIA) was used to measure plasma concentrations.
- Samples were collected from newborn infants and children up to puberty.
- Maternal plasma and adult blood donor plasma served as controls.
Main Results:
- Mean maternal TBG (1.65 mg/100 ml) was significantly higher than cord blood TBG (1.16 mg/100 ml).
- Infant and childhood TBG levels were significantly elevated compared to adult controls.
- Postnatal T3 and T4 increases were not attributed to concurrent TBG level changes.
Conclusions:
- Maternal TBG concentrations exceed those in cord blood.
- Elevated TBG persists throughout childhood, suggesting developmental regulation.
- Neonatal thyroid hormone surges are independent of TBG fluctuations.
Abstract:
Thyroxine-binding globulin (TBG), triiodothyronine (T3), thyroxine (T4) and thyrotropin (TSH) have been determined by radioimmunoassay in plasma of newborn infants and throughout childhood until puberty. Mean maternal TBG concentration was 1.65 +/- 0.09 mg/100 ml (SEM) and significantly higher (p less than 0.01) than cord blood levels of TBG (1.16 +/- 0.08 mg/100 ml (SEM). Throughout infancy and childhood TBG remained significantly elevated (p less than 0.01) compared to a middle age control group of healthy blood donors. T3, T4 and TSH concentrations behaved postnatally as known from previous studies. The T3 and T4 increase observed immediately after birth was not a secondary phenomenon due to changes in TBG concentration since this globulin did not change significantly during this period.