Although the placenta is only a limited barrier for the transfer of thyroxine (T4) to the fetus, we have recently demonstrated that maternal T4 does not suffice to prevent the effects of in utero hypothyroidism. The current study presents a convenient and minimally invasive animal model to study whether maternal-fetal transfer of T4 administered to the pregnant rat corrects the newborn's in utero hypothyroidism. In this model pregnant rats receive the goitrogen methimazole in their drinking water from d 10 of gestation until birth, either alone or together with L-T4. Circulating T4 levels in the dams and newborn pups are measured from blood spotted on filter paper by RIA. Using blood T4 levels as the measure, in the present study we found similar effects for orally and intraperitoneally administered T4. This rat model will allow future studies of whether maternal-fetal T4 transfer can correct the detrimental neurobehavioral effects of intrauterine hypothyroidism.

Objective: To assess whether complete kangaroo mother care (KMC), a skin-to-skin contact intervention, would affect longitudinal/developmental patterns of hormonal change. Method: An open randomized controlled trial was conducted in a large tertiary care hospital, comparing KMC and traditional care for newborn infants weighing less than 2,001 g. Eighty-seven healthy preterm (<37 weeks gestational age) infants from this study provided three blood-spot samples on filter paper: at randomization (postnatal age 1–5 days), 2 weeks later, and at calculated term (41 weeks gestational age). They met a number of additional inclusion criteria including discharge from the hospital within the first postnatal week. The levels of 17α-hydroxy-progesterone (17-OHP), thyroxine-stimulating hormone (TSH) and thyroxine (T₄) were assessed by radioimmunoassay. Birth weight (<1,800 or ≧1,800 g) and prenatal maternal corticosteroid treatment were taken into account in the analysis. Interventions: Complete KMC includes early discharge, positioning the infant on the parent’s chest in an upright position, 24 h/day in skin-to-skin contact, and breast-feeding. In the traditional care group, infants were discharged according to routine hospital practice. Results: Levels of 17-OHP and TSH decreased significantly from eligibility to calculated term while T₄ levels did not change significantly over time. Most importantly, overall, treatment (KMC) did not interact with the pattern of physiological change. Conclusions: Maturation of the pituitary-thyroid axis and adrenal function is apparently not compromised by KMC, at least in healthy preterm infants.

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