Introduction: Research indicates a strong link between obesity and alterations in thyroid function among patients diagnosed with obstructive sleep apnea-hypopnea syndrome (OSAHS). Our study aims to investigate the thyroid hormone levels in patients with OSAHS combined with obesity. It seeks to elucidate the changes in thyroid hormones and their potential metabolic risks in these patients, thereby further clarifying the role and clinical significance of thyroid function alterations in OSAHS complicated by obesity.

Methods: One hundred and thirty-four patients were divided into four groups, including the normal group, the obesity group, the OSAHS with the obesity group, and the OSAHS group. Serum levels of free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) were analyzed using electrochemiluminescence immunoassay. Clinical metabolic parameters (total cholesterol [TC], triglycerides [TG], high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C]) and sleep respiratory monitoring indicators (apnea-hypopnea index [AHI], longest duration of sleep apnea [TAmax], oxygen desaturation index [ODI], mean oxygen saturation [M-SaO₂], and lowest oxygen saturation [L-SaO₂]) were also recorded.

Results: The OSAHS with the obesity group demonstrated elevated FT3, TSH, and ODI levels but lower L-SaO₂ level than other groups, and the levels of TG and LDL-C were higher than those in the OSAHS group and the normal group. Additionally, TSH level was positively correlated with LDL-C and BMI, but negatively correlated with L-SaO₂. In the obesity group, FT3, TSH, TG, ODI, and TAmax levels were higher, while L-SaO₂ and M-SaO₂ were lower than those in the normal group.

Conclusions: Patients with both OSAHS and obesity are at higher risk of developing subclinical hypothyroidism, with LDL-C, BMI, and L-SaO₂ levels likely contributing to changes in TSH levels.