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Effect of breast-feeding on infant thyroid activity: 3 year follow up--longitudinal study
Insights
Breast-feeding impacts infant thyroid hormones, with higher T4 and rT3 observed in breast-fed infants. These thyroid function effects persist for years, influencing hormone levels and TSH in toddlers.
Area of Science:
- Endocrinology
- Pediatrics
- Nutrition Science
Background:
- Thyroid hormones are crucial for infant development.
- Breast-feeding is a primary nutrition source for infants.
- Longitudinal data on breast-feeding's long-term thyroid effects is limited.
Purpose of the Study:
- To investigate the longitudinal effects of breast-feeding on serum thyroid hormones (T3, T4, rT3) and TSH in infants up to 3 years.
- To correlate thyroid hormone levels and TSH with the duration and timing of breast-feeding and weaning.
Main Methods:
- A longitudinal study design was employed.
- Serum thyroid hormones (T3, T4, rT3) and TSH levels were measured in infants from birth to 3 years.
- Infants were categorized based on breast-feeding status and age of weaning.
Main Results:
- Breast-fed infants showed higher T4 at 4-6 months and higher rT3 at 4 months compared to weaned infants.
- Lower body weight was noted in breast-fed girls at 4-6 months.
- Later weaning correlated with higher T4 in 1-2-year-olds and influenced rT3 and TSH levels at 2-3 years.
Conclusions:
- Breast-feeding exerts immediate effects on infant thyroid function parameters.
- Some observed thyroid function alterations persist into early childhood (1-3 years).
- The age of weaning is a significant factor in long-term thyroid hormone regulation.
Abstract:
The effect of breast-feeding on serum thyroid hormones and TSH was studied in a longitudinal study from birth up to 3 years. T4 was found to be significantly higher in breast-fed than in weaned infants at the age of 4 and 6 months and so was rT3 at the age 4 months. The body weight of breast-fed girls at the age 4 and 6 months was lower than that of formula-fed ones. Breast-feeding at the age 9 months resulted in a decreased serum TSH. Serum T3 of infants weaned before the end of the first week of life was higher than in other groups of infants at the age of 10 weeks. Serum T4 of children 1-2-year-old correlated positively with the age at weaning, provided that they had been breast-fed at least for 60 days. Serum rT3 of 2-year-old children also correlated with the age of weaning. Serum TSH at the age of 3 years was higher in children who had been weaned during first 60 days of life than in those weaned later. It is concluded that breast-feeding possess some immediate effects on thyroid function parameters. Some effects were still detected at the age of 1-3 years.