Abstract
BackgroundSeveral factors may influence newborn thyroid-stimulating hormone (TSH) concentrations and cause subclinical hypothyroidism in a newborn. A sufficient level of leptin signalling is needed for the normal production of TSH and thyroid hormones by the thyroid gland. Our study aimed to investigate the correlation between maternal serum leptin concentration during the third trimester of pregnancy and newborn screening-TSH levels.MethodsThis prospective cross-sectional study was conducted in obstetrics and gynaecology clinics of a state hospital between June and August 2013. Maternal venous blood samples were collected from 270 healthy pregnant women in the third trimester just before delivery. Measurements of maternal fT3, fT4, TSH, anti-thyroid peroxidase (TPO), and anti-thyroglobulin (anti-Tg) antibodies from serum samples were performed by chemiluminescence immunoassay. Maternal serum leptin levels were determined by ELISA. Dried capillary blood spots were used to measure newborn TSH levels.ResultsSubjects were divided into two groups according to the neonatal TSH levels using a cut-point of 5.5 mIU/L. Median maternal serum leptin levels were significantly higher in newborns whose TSH levels were higher than >5.5 mIU/L [13.2 μg/L (1.3 - 46.5) vs 19.7 μg/L (2.4 - 48.5), p<0.05]. Serum leptin levels showed a negative correlation with maternal fT4 (r=0.32, p<0.05), fT3 (r=0.23, p<0.05), and a positive correlation with BMI (r=0.30, p<0.05).ConclusionsOur results suggest that high leptin levels in the third trimester of pregnancy influence maternal thyroid functions and might cause an increase in newborn TSH levels. Detection of high maternal serum leptin levels may be a reason for subclinical hypothyroidism.
Highlights
Adipose tissue is an active endocrine organ that secretes various bioactive hormones called adipokines with multiple metabolic, neuroendocrine, cardiovascular, and inflammatory functions [1]
Our results suggest that high leptin levels in the third trimester of pregnancy influence maternal thyroid functions and might cause an increase in newborn thyroid-stimulating hormone (TSH) levels
In the paraventricular nucleus of the hypothalamus, leptin has a regulatory role in the expression and secretion of thyrotropinreleasing hormone (TRH); it has a regulatory effect on thyroid-stimulating hormone (TSH) and thyroid hormone production [3]
Summary
Adipose tissue is an active endocrine organ that secretes various bioactive hormones called adipokines with multiple metabolic, neuroendocrine, cardiovascular, and inflammatory functions [1]. Leptin is a hormone that is exclusively secreted by adipose tissue and encoded by the ob gene. Leptin has a vital role in the regulation and synthesis of thyroid hormones. Several other factors may influence newborn TSH concentrations and cause mild hypothyroidism. Maternal hypothyroidism [5], maternal medications, blocking antibodies [6], body mass index (BMI), and smoking [7], as well as weight gain during pregnancy [8], are well-known factors that may affect newborn thyroid function. Increasing adipose tissue stores and secretion from the placenta results in elevated concentrations of leptin [9], which peaks at the end of the second or beginning of the third trimester and remains stable after that until delivery [10]. Leptin was suggested to play the primary role as a regulator of fetal growth and development [11]
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