AUTHOR=Liu Zhao-min , Li Guoyi , Wu Yi , Zhang Di , Zhang Sujuan , Hao Yuan-Tao , Chen Weiqing , Huang Qi , Li Shuyi , Xie Yaojie , Ye Mingtong , He Chun , Chen Ping , Pan Wenjing 

TITLE=Increased Central and Peripheral Thyroid Resistance Indices During the First Half of Gestation Were Associated With Lowered Risk of Gestational Diabetes—Analyses Based on Huizhou Birth Cohort in South China

JOURNAL=Frontiers in Endocrinology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2022.806256

DOI=10.3389/fendo.2022.806256

ISSN=1664-2392

ABSTRACT=Objectives
The study aims to explore the relationship of thyroid function and resistance indices with subsequent risk of gestational diabetes (GDM).
Design
This was a longitudinal study embedded in the Huizhou Birth Cohort.
Methods
Total 2927 women of singleton pregnancy were recruited from January to October of 2019. Thyroid central resistance indices were evaluated by Thyroid Feedback Quartile-based index (TFQI), Thyrotrophy T4 resistance index (TT4RI) and TSH index (TSHI) based on plasma free thyroxine (FT4) and thyroid stimulating hormone (TSH) levels during the first half of pregnancy. Thyroid peripheral sensitivity was assessed by free triiodothyronine (FT3) to FT4 ratio (FT3/FT4), a proxy of deiodinase activity. GDM was diagnosed between 24 to 28 weeks of gestation by a standardized 75g oral glucose tolerance test. Multivariable linear and logistic regression was applied to examine the associations of thyroid markers with GDM risk.
Results
FT3 and FT3/FT4 were positively associated with both fasting and post-load glucose levels, while TSH, TSHI, TT4RI and TFQI were negatively associated with 1 and 2 hrs post-load glucose levels. Compared with the lowest quartile, GDM risk in the highest quartile increased by 44% (OR=1.44，95%CI：1.08-1.92, Ptrend=0.027) for FT3, and 81% (OR=1.81，95%CI: 1.33-2.46, Ptrend<0.001) for FT3/FT4, while lowered by 37% (OR=0.63, 95%CI: 0.47-0.86, Ptrend=0.002) for TSHI,  28% for TT4RI (OR=0.72，95%CI：0.54-0.97, Ptrend=0.06) and 37% for TFQI (OR=0.63, 95%CI：0.46-0.85, Ptrend<0.001). 
Conclusions
This longitudinal study indicated that higher FT3 and FT3/FT4, while lower central thyroid resistance indices were associated with increased risk of GDM.