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Thyroid hormones in milk: physiological approach--a review.
Endocrinologia Experimentalis
|October 1, 1983
Summary
Maternal milk impacts thyroid function in infant rats, suggesting exogenous thyroid hormone intake. While lactation affects maternal thyroid hormones, its influence on infant thyroid function is less clear.
Area of Science:
- Endocrinology
- Neonatal Physiology
- Comparative Physiology
Background:
- Thyroid hormone levels in human milk vary, with questions regarding assay specificity.
- Lactation is known to induce physiological changes in maternal thyroid function.
Purpose of the Study:
- To investigate the effects of maternal milk on infant thyroid function.
- To examine the impact of milk secretion on maternal thyroid economy.
- To explore potential exogenous thyroid hormone transfer via maternal milk.
Main Methods:
- Studies in lactating and thyroidectomized rats with varying litter sizes and milk intake.
- Longitudinal follow-up of over 80 human infants from birth to 12 months, analyzing thyroid parameters based on feeding type.
- Assessing human milk's thyroid activity by feeding it to thyroidectomized rats.
Main Results:
- Rat pups from litters with higher milk consumption showed accelerated maturation, suggesting exogenous thyroid hormone intake.
- Lactating women exhibited lower thyroxine (T4) and higher thyroid-stimulating hormone (TSH) compared to non-lactating women.
- Infants showed minor thyroid parameter differences (e.g., elevated reverse T3 at 4 months in breastfed infants).
Conclusions:
- Lactation significantly alters maternal thyroid hormone economy.
- Maternal milk demonstrably affects thyroid function in infant rats.
- The impact of maternal milk on infant thyroid function in humans is subtle and challenging to ascertain definitively.