Effect of Bisphenol A-Mediated RBP-4 on Pregnancy Outcomes in Nonobese Pregnant Female with Subclinical Hypothyroidism

Hypothyroidism is a systemic hypometabolic syndrome caused by the thyroxine resistance or a reduction in its extent. It is an endocrinopathy secondary to gestational diabetes and occurs usually without significant symptoms. This study explored the effect of bisphenol A (BPA)-mediated retinol-binding protein 4 (RBP-4) on pregnancy outcomes in a nonobese pregnant female with subclinical hypothyroidism. Three hundred nonobese pregnant females who had that established pregnancy files and had regular obstetric examinations from January 2021 to March 2022 were enrolled and classified with 100 cases in each group as early pregnancy (6–12 weeks of gestation), second-trimester (13–24 weeks of gestation), and third-trimester groups (25–36 weeks of gestation). Thirty pregnant women with subclinical hypothyroidism were selected as subjects, and another thirty pregnant women with normal thyroid function were selected as the normal control group. Thyroid function (thyroid-stimulating hormone (TSH), free triiodothyronine (FT(3)), free T(4) (FT(4)), and thyroid peroxidase antibody (TPO-Ab)) was measured by immunoelectrochemiluminescence. The level of BPA in urine was determined by solid-phase extraction high-performance liquid chromatography-tandem mass spectrometry. Serum RBP4 levels were determined by enzyme-linked immunosorbent assay. The level of TSH in the third-trimester group was higher than that in the first- and second-trimester groups, while the levels of FT(3), FT(4), and TPO-Ab were lower than those in the other two groups (P < 0.05). TSH in the second-trimester group was higher than that in the first-trimester group, while FT(3), FT(4), and TPO-Ab levels were lower than those in the first-trimester group (P < 0.05). The levels of BPA and RBP4 in gestational diabetes mellitus and hypertension were higher than those in the nongestational period, and the levels of BPA and RBP4 in gestational intrahepatic cholestasis and anemia were higher than those in the nongestational period, and the levels of BPA and RBP4 in preterm delivery were higher than those in nongestational period (P < 0.05). Also, the level of urinary BPA in the hypothyroidism group was higher than that in the normal control group (P < 0.05) and the level of serum RBP4 in the hypothyroidism group was higher than that in the normal control group (P < 0.05). According to multivariate logistic regression analysis, age ≥30 years and the ascending BPA and RBP4 were risk factors for subclinical hypothyroidism during pregnancy in the nonobese female. BPA and RBP-4 are closely related to the pregnancy outcome of nonobese subclinical hypothyroidism in the pregnant female. The degree of BPA and RBP-4 in adverse pregnancy outcomes is increased, which is the risk factor for nonobese subclinical hypothyroidism.