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

Abstract

ObjectivesThe study aimed to explore the relationship of thyroid function and resistance indices with subsequent risk of gestational diabetes (GDM).DesignThis was a longitudinal study embedded in the Huizhou Birth Cohort.MethodsA total of 2,927 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 and 28 weeks of gestation by a standardized 75 g oral glucose tolerance test. Multivariable linear and logistic regression was applied to examine the associations of thyroid markers with GDM risk.ResultsFT3 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 h post-load glucose levels. Compared with the lowest quartile, GDM risk in the highest quartile increased by 44% [odds ratio (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 it 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).ConclusionsThis longitudinal study indicated that higher FT3 and FT3/FT4 and lower central thyroid resistance indices were associated with increased risk of GDM.

Association between sensitivity to thyroid hormone indices and the risk of osteoarthritis: an NHANES study

“…FT3 to FT4 ratio (FT3/FT4) can estimate the conversion efficiency of FT4 to FT3, which indirectly reflects the peripheral sensitivity of thyroid hormones. Increasing attention has been paid to the relationship between thyroid hormone sensitivity and metabolic disorders in recent years, and sensitivity to thyroid hormone indices have been proved to be reliable predictors of insulin resistance, type 2 diabetes (T2D), cardiometabolic risk, and disorders of glucose and lipid metabolism [20][21][22]. However, studies investigating the relationship between sensitivity to thyroid hormone indices and OA have not been reported.…”

Higher Thyroid fT3-to-fT4 Ratio Is Associated with Gestational Diabetes Mellitus and Adverse Pregnancy Outcomes

“…It is suggested that thyroid dysfunction may have a role in the emergence of GDM [ 4 , 5 ]. However, data are sparse on the association between different thyroid function markers and GDM based on the 2013 WHO criteria [ 12 , 13 ]. Data are also limited on the impact of thyroid function within the normal range on pregnancy outcomes and the risk of developing glucose intolerance in early postpartum.…”

“…A study of Rawal et al showed that higher fT3 levels may be an indicator of GDM risk starting early into pregnancy [ 5 ]. A recent Chinese study showed that both peripheral and central thyroid resistance indices during the first half of pregnancy significantly affected the subsequent risk of GDM [ 13 ]. This study showed that higher levels of fT3 and a higher fT3-to-fT4 ratio were associated with increased GDM risk, even among euthyroid women [ 13 ].…”

“…A recent Chinese study showed that both peripheral and central thyroid resistance indices during the first half of pregnancy significantly affected the subsequent risk of GDM [ 13 ]. This study showed that higher levels of fT3 and a higher fT3-to-fT4 ratio were associated with increased GDM risk, even among euthyroid women [ 13 ]. However, this study investigates a Chinese population, though we also present the first data on the impact of TH markers on the risk of developing GDM in a Caucasian population using the 2013 WHO criteria.…”

“…More data are needed to evaluate the association between thyroid function during pregnancy with GDM, adverse pregnancy outcomes, and risk of developing glucose intolerance in early postpartum. Moreover, there are currently only a few studies on the association between TH markers and GDM based on the 2013 WHO criteria [ 12 , 13 ]. We therefore aimed to determine the association between the fT3-to-fT4 ratio and related TH markers in early and late pregnancy and the risk of developing GDM, adverse pregnancy outcomes, and glucose intolerance in early postpartum.…”