Yushan Xie,1,2,* Hongli Zhang,3,* Zine Cao,1,* Yanuo Zhou,1,2 Chendi Lu,1,2 Libo Yin,4 Simin Zhu,1,2 Yonglong Su,1,2 Xiaoxin Niu,1,2 Lina Ma,1,2 Yuqi Yuan,1,2 Yitong Zhang,1,2 Zitong Wang,1,2 Haiqin Liu,1,2 Xiaoyong Ren,1,2 Yewen Shi1,2 

1Department of Otorhinolaryngology—Head and Neck Surgery, The Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, People’s Republic of China; 2Shaanxi Provincial Key Laboratory for Precision Diagnosis and Treatment of Otorhinolaryngology, Xi’an, People’s Republic of China; 3Department of Ultrasound, The Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, People’s Republic of China; 4Otolaryngology Head and Neck Surgery Department, Xi’an Central Hospital, Xi’an, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Xiaoyong Ren, The Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, People’s Republic of China, Email renxiaoyong@sina.vip.com Yewen Shi, The Second Affiliated Hospital of Xi’an Jiaotong University, Xi’an, People’s Republic of China, Email shiyewen59@outlook.com

Purpose: This study unveils the complex interplay among obstructive sleep apnea (OSA), thyroid function, and morphological changes.
Methods: Data from 1,102 patients were collected retrospectively from the Department of Otorhinolaryngology—Head and Neck Surgery of the Second Affiliated Hospital of Xi’an Jiaotong University from 2012 to 2023. The patients were divided into severe and non-severe OSA groups according to their polysomnography results. The data were analyzed by sex and age stratification.
Results: Serum free triiodothyronine (FT3), total triiodothyronine (TT3), and reverse triiodothyronine (RT3) were higher in severe OSA group in the total population (p < 0.05). Similar trends were observed in male but not in female. FT3 and TT3 are higher in the severe group in the nonelderly population (age < 60) (p < 0.05), and RT3 is higher in the severe group in the elderly population (age ≥ 60) (p < 0.05). In addition, we first reveal that RT3 is associated with the diameter of the left inferior thyroid artery (L-ITA) (r=0.394, p < 0.05) and lowest transcutaneous oxygen saturation at night (lowest SpO2) (r=− 0.269, p < 0.05). The severe OSA group showed larger thyroid volume and isthmus length, as well as the thicker ITA diameter and lower left thyroid lobe resistance index (RI) (all p < 0.05).
Conclusion: Our study demonstrates a significant association between thyroid function/morphology and OSA, with distinct sex- and age-related differences. Reduced RI in severe OSA suggests its clinical utility in assessing vascular health. Increased thyroid volume and isthmus length in severe OSA may reflect ITA-related changes. These findings support our prior observations of rising thyroid hormone levels with OSA progression and highlight the need for sex- and age-stratified analyses. Integrated evaluation of thyroid function and morphology is essential for understanding OSA-thyroid pathophysiology.

Keywords: obstructive sleep apnea, thyroid function, thyroid morphology, inferior thyroid artery