Increasing maternal obesity is associated with alterations in both maternal and neonatal thyroid hormone levels

Abstract

Objective Obesity is associated with alterations in thyroid hormone (TH) levels in obese, pregnant individuals. The maintenance of TH levels throughout gestation is important for proper fetal development. The aim of this study was to measure levels of fT3, fT4 and TSH in maternal and matched cord blood serum from normal weight, overweight and obese gravidae to determine alterations in maternal and neonatal TH levels by virtue of maternal obesity. Design, Setting, Subjects, Outcome Measures ELISA was utilized to measure fT3, fT4 and TSH levels from banked, matched maternal and neonatal (cord blood) serum (N=205 matched pairs). Data was stratified according to pre-pregnancy or first trimester BMI. Results Both maternal and neonatal fT3 levels consistently increased with increasing maternal obesity, and maternal and neonatal fT3 were significantly correlated (r =0.422, p<0.001). Maternal and neonatal fT3 were also significantly associated with birthweight (β=0.155, p=0.027 and β=0.171, p=0.018 respectively). Both the maternal and neonatal fT3 to fT4 ratio significantly increased with increasing maternal obesity. We further found that excess gestational weight gain was associated with a decrease in maternal fT4 compared with gravidae who had insufficient gestational weight gain (0.86±0.17 vs. 0.95±0.22, p<0.01). Conclusion Maternal obesity is not only associated with maternal alterations in TH, but with accompanying neonatal changes. Because both maternal obesity and alterations in TH levels are associated with childhood obesity, based on these findings and our prior analyses in a non-human primate model we propose that changes in fT3 levels in the offspring of obese mothers may be a potential molecular mediator of fetal overgrowth and childhood obesity.

Isolated Maternal Hypothyroxinemia and Adverse Pregnancy Outcomes: A Systematic Review

“…In this respect, in iodine de cient mothers, the thyroid gland shifts its secretion from T4 to T3 to maintain iodine; consequently, IMH is more prevalent in iodine de ciency (9,31). However, other novel factors, including exposure with environmental pollutants which may activate the hepatic glucuronidation, competitive inhibition of sodium iodine symporter and binding to the nuclear thyroid hormone receptor (32)(33)(34)(35), obesity leading to increased peripheral deiodination (36)(37)(38)(39)(40), iron de ciency due to reduced activity of the heme-dependent thyroid (41)(42)(43)(44), peroxidase antibodies (21) and pro/antiangiogenic factors (45) are associated with increased risk of IMH.…”

TSHβX1 Splice Variant Expression and D2 Thr92Ala Polymorphism Analysis in Pregnant Women with Thyroid Diseases

“…The thyroid diseases do not have a unique origin; genetic, endogenous, and environmental factors are involved [15,16]. It has been previously published that a relationship between obesity and hypothyroidism in which leptin levels intervene and in which TSH is directly responsible for weight gain [17].…”

Maternal smoking and high BMI disrupt thyroid gland development

“…The second trimester marks a critical developmental window when the fetal thyroid gland begins to assume its critical endocrine functions. Two major maternal lifestyle factors, smoking and being overweight, have been implicated in the disruption of thyroid function in the neonate [18][19][20]. However, the mechanisms linking maternal smoking and increased maternal weight to thyroid disruption are largely unknown.…”