Association between triglyceride glucose-waist height ratio index, hypothyroidism, and mortality in individuals with hypothyroidism: data from NHANES 2007-2012

Background: The aim of this study was to examine the associations between the triglyceride glucose-waist height ratio (TyG-WHtR) index and hypothyroidism, as well as mortality among individuals with hypothyroidism. Methods: Data collected from the National Health and Nutrition Examination Survey (NHANES) database spanning the years 2007 to 2012. 8,437 nonpregnant adults were included in the study. Logistic regression models, cox regression models and restricted cubic spline analyses (RCSs) , as well as Subgroup analysis were employed. Results: Individuals in the fourth quartile of TyG-WHtR had a higher odds ratio (OR) of 1.91 (95% CI= 1.08 ~ 3.39, P =0.026) for subclinical hypothyroidism and an OR of 2.41 (95% CI= 1.03 ~ 5.59, P =0.041) for overt hypothyroidism compared to those in the first quartile. RCSs revealed a linear relationship between TyG-WHtR and subclinical hypothyroidism ( P -overall=0.01) and a strong nonlinear association between TyG-WHtR and overt hypothyroidism ( P for nonlinearity= 0.043). Cox regression models demonstrated that the adjusted HR for all-cause mortality across the lowest to highest tertiles of TyG-WHtR were 1.00 (reference), 1.59 and 2.40, respectively ( P = 0.035). Similar results of the adjusted HR and 95% CI for CVD mortality were revealed ( P = 0.041). Subgroup analysis indicated significant interactions between the TyG-WHtR and age, BMI (all P interaction< 0.05) in relation to the all-cause and CVD mortality among those with hypothyroidism. Conclusion: TyG-WHtR exhibited a positive association with an elevated incidence of hypothyroidism. Furthermore, among participants with hypothyroidism, this index was linked to all-cause and CVD mortality.