Infant feeding, fetal growth and adult thyroid function

Abstract

Prolonged breast-feeding in humans is associated with increased low-density lipoprotein cholesterol and higher death rates from ischaemic heart disease in adult life. The reasons for this link are unclear. A possible explanation is that thyroid hormones present in breast milk and absorbed by the suckling infant could, by the process of hormonal imprinting, permanently down-regulate the set point of thyroid homeostasis. Thyroid hormones influence cholesterol metabolism, and could explain the link between infant feeding and the regulation of cholesterol levels in the adult. We therefore investigated whether infant feeding was related to adult thyroid function in 303 women aged 60–71 years who were born in the county of Hertfordshire, UK, where birthweight, the weight at 1 year and the method of infant feeding had been recorded routinely. Free thyroxine (FT4) concentrations but not free triiodothyronine (FT3) or thyrotrophin (TSH) were increased in the women who, as infants, had been breast-fed beyond 1 year of age (p <0.01). In women who were bottle-fed, with or without breast-feeding, serum TSH rose and FT4 fell with increasing birthweight (p=0.01 and p=0.04, respectively). Although the metabolic significance of these findings is unclear, they suggest that the set point of thyroid function in the adult is determined by fetal growth and infant feeding.

Regulation of the Pituitary-Thyroid Axis in Adulthood Is Not Related to Birth Weight: Evidence from Extremely Birth Weight–Discordant Monozygotic Danish Twin Pairs

“…When twins were investigated as singletons, birth weight was inversely associated with serum FT4 and T3, which is in agreement with the observation made in bottle-fed women by Phillips et al (7). However, analyses of the complete study population showed no within-pair differences in serum TSH or T3, but FT4 was higher in those with the lowest birth weight.…”

“…Furthermore, it has been suggested that fetal growth and feeding influence thyroid function in adults, emphasizing that the interaction between early life factors and adult health is complex. Thus, in the Hertfordshire Cohort, breast-feeding beyond 1 year of age was associated with higher free thyroxine (FT4) levels, whereas an inverse association between birth weight and FT4 was detected in women who had been bottle-fed (7 Thyroid function variables show substantial inter-individual variability, and each individual has a set point, at which secretion of thyroid-stimulating hormone (TSH) is changed (8,9). Due to the deviating and limited information retrieved from the above studies, the aim of the present investigation was to provide insight into the potential association between birth weight and the pituitary-thyroid axis set point in adults.…”

MECHANISMS IN ENDOCRINOLOGY: Neurodevelopmental disorders in children born to mothers with thyroid dysfunction: evidence of fetal programming?

“…Thyroid hormone abnormalities and thyroid autoimmunity have been considered both as the outcome and as the exposure in a fetal programing hypothesis. A number of studies, including studies in twins, have evaluated the association between birth weight and adult thyroid function as the outcome, and some studies have reported an association between fetal growth characteristics and the later presence of thyroid autoantibodies and adult thyroid function (25,26), whereas others found no association (27,28,29).…”

Adaptive changes in thyroid function of female rats fed a high-fat and low-protein diet during gestation and lactation

“…Some investigators have shown that the nutritional status of the mother during the gestational and lactational periods is essential to normal growth and development in humans (6)(7)(8) and in experimental animals (9)(10)(11)(12)(13)(14)(15).…”