Background: Neonatal jaundice is strongly attributable to excess body-weight loss as a result of insufficient calorific intake. Objectives: To examine the incidence of neonatal jaundice (defined by use of phototherapy) and body-weight loss, as well as their association, among neonates under optimal thermal control with sufficient nutrition, a local protocol for temperature and nutritional regulation. Methods: We retrospectively identified a cohort of 10,544 neonates (birth weight ≥2,500 g) placed in thermo-controlled incubators for 2 h immediately after birth. Neonates were fed with 5% glucose solution 1 h after birth and breastfed every 3 h (with supplementary formula milk if applicable) according to basal maintenance expenditure. Total serum bilirubin levels at day 4 (peak level) were assessed. Phototherapy was performed on the basis of total serum bilirubin level ≥18 mg/dL. Risk ratio (RR) and 95% CI for the use of phototherapy against maximum body-weight loss were estimated using Poisson regression with robust variance. Results: Incidence of phototherapy use was low (0.3%) and the mean total serum bilirubin level was 8.5 mg/dL (SD 2.7 mg/dL), with a low mean maximum body-weight loss (1.9%) and low incidence of excess body-weight loss ≥7% (0.4%). Maximum body-weight loss was associated with risk of neonatal jaundice (RR 1.27; 95% CI 1.04–1.54), and became significant at approximately 4% of maximum body-weight loss. Conclusion: Optimal thermal control and sufficient nutrition may greatly reduce the incidence of neonatal jaundice by preventing neonatal body-weight loss.

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Abstract. Thyroid peroxidase (TPO) is an essential enzyme involved in thyroid hormone synthesis and is closely related to the microsomal antigen which is the target of thyroid microsomal antibody. There have been several reports on direct inhibition of peroxidase activity by thyroid microsomal antibody. We prepared a mini organ culture of thyroid glands obtained at operation, and investigated the localization of thyroid peroxidase activity in follicular cells proliferated around the thyroid tissue blocks by electron microscopy. The development of microvilli containing TPO activity on the cell surface facing the culture medium was observed when normal thyroid tissue or Graves' thyroid tissue was incubated with TSH but in the TSH-free group the development of microvilli was poor and TPO activity was very much decreased. After the addition of serum positive for thyroid microsomal antibody, the TPO activity of the microvilli was retained in 4/6 tissue samples, but it disappeared in 2 cases. Our findings suggested that thyroid peroxidase activity is regulated by thyroid stimulating substances such as TSH and by TPO in tissue.

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