Abstract
<jats:p>Background: Female urinary incontinence (UI) is a prevalent disorder associated with pelvic floor dysfunction. The abnormalities in neuromuscular function that cause the clinical symptoms of UI are rarely thought to be related to metabolic function, and may be especially related to thyroid hormone levels. Objective: To examine the connection among thyroid function, thyroid homeostasis parameters, and UI, along with its various subtypes in females. Methods: A total of 3,443 adult females who participated in the National Health and Nutrition Examination Survey from 2007 to 2012 were included. Further classification of the UI group was made into urge urinary incontinence (UUI), stress urinary incontinence (SUI), and mixed urinary incontinence (MUI). Thyroid homeostasis parameters, such as thyroid feedback quantile index (TFQI), were calculated from thyroid hormones to reflect thyroid hormone sensitivity. To examine the associations among thyroid function, thyroid homeostasis parameters and UI, we utilized weighted multivariate logistic regression and restricted cubic splines in the analysis. Results: Thyroid stimulating hormone was significantly negatively correlated with UI (OR = 0.97, 95% CI: 0.96-0.99, p = 0.006), while TFQIFT3 showed a U-shaped association with UI (p for nonlinear = 0.014). In the analysis of subtypes, the FT3/FT4 ratio showed a negative correlation with UUI and MUI, evidenced by a J-shaped relationship, with change points identified at 0.301(p for all = 0.033, p for nonlinear =0.031; p for all = 0.010, p for nonlinear =0.005). Subgroup analysis showed consistent associations, and there was an interaction between BMI and FT3/FT4 ratio and UUI (p for interaction < 0.05). Conclusions: The FT3/FT4 ratio may serve as a promising biomarker for assessing the risk of UUI and MUI. The associations among thyroid dysfunction, thyroid homeostasis, and UI in women suggest varying patterns across different UI subtypes.</jats:p>