The prevalence of non-alcoholic fatty liver disease (NAFLD) significantly increases in patients with type 2 diabetes mellitus (T2DM). However, the correlation of NAFLD with visceral fat area (VFA) and thyroid nodules in T2DM patients has been rarely reported.

This study aims to investigate the influencing factors for NAFLD in T2DM patients, and the correlation of NAFLD with VFA, thyroid nodules, and thyroid function in this population.

Hospitalized T2DM patients in the Department of Endocrinology, the Fourth Affiliated Hospital of Guangxi Medical University (Liuzhou Worker's Hospital) from January 2018 to April 2023 were retrospectively recruited. They were divided into two groups based on abdominal ultrasound findings: NAFLD group and non-NAFLD group. General data, including VFA, subcutaneous fat area (SFA), insulin function, thyroid function, prevalence of thyroid nodules, blood glucose levels, lipid levels, and liver and kidney function were compared between the two groups. Additionally, patients were divided into visceral obesity group (VFA≥100 cm²) and non-visceral obesity group (VFA < 100 cm²) based on VFA. Age, sex, prevalence of NAFLD and thyroid nodule were compared between the two groups. Spearman correlation analyses were employed to investigate factors associated with NAFLD and VFA, as well as their correlation with thyroid nodules. Influencing factors for the volume of thyroid nodules were explored as well. Furthermore, binary Logistic regression analysis was used to determine risk factors for both NAFLD and thyroid nodules in T2DM patients. Receiver operating characteristic (ROC) curve analysis evaluated the predictive value of BMI, waist-hip circumference, and waist-hip ratio, VFA, homeostatic model assessment for insulin resistance (HOMA-IR) in predicting NAFLD in T2DM patients and their optimal cut-off values.

A total of 578 T2DM patients were enrolled in this study, including 293 (50.69%) patients in the NAFLD group and 285 in the non-NAFLD group. The age of the NAFLD group was significantly lower than that of non-NAFLD group [ (57.0±12.8) years vs. (59.3±11.6) years, P<0.05]. Compared to those of the non-NAFLD group, patients in the NAFLD group had significantly higher body weight, body mass index (BMI), waist circumference, hip circumference, VFA, SFA, glycated hemoglobin (HbA_1c), fasting insulin levels (FINS), fasting C-peptide levels (FCP), HOMA-IR, homeostasis model assessment of β-cell function (HOMA-β), free triiodothyronine levels (FT₃), serum uric acid (SUA), total cholesterol (TC), triglyceride (TG) and C-reactive protein (CRP), but significantly lower serum creatinine (SCr) (P<0.05). There were 251 cases in the visceral obesity group and 327 cases in the non-visceral obesity group. The age of the visceral obesity group was significantly lower than that of the non-visceral obesity group [ (55.3±13.4) years vs. (60.3±10.8) years, P<0.05]. The incidence of NAFLD was significantly higher in the visceral obesity group than that of non-visceral obesity group (P<0.05). However, there was no significant difference in the prevalence of thyroid nodules between the visceral obesity group and non-visceral obesity group (64.94% vs. 59.82%, P>0.05). Spearman correlation analysis revealed that the occurrence of NAFLD in T2DM patients was positively correlated with body mass, BMI, waist circumference, hip circumference, waist-to-hip ratio, VFA, SFA, HbA_1c, FINS, FCP, HOMA-IR, HOMA-β, total triiodothyronine (TT₃), FT₃, and CRP (P<0.05), but negatively correlated with age (P<0.05). VFA in T2DM patients was found to be significantly correlated with gender, age, height, body mass, BMI, waist circumference, hip circumference, waist-to-hip ratio, SFA, diastolic blood pressure (DBP), FINS, FCP, HOMA-IR, HOMA-β, TT₃, FT₃, CRP and NAFLD (P<0.05). The thyroid nodule area showed a negative correlation with height, thyroid stimulating hormone (TSH) and waist-to-hip ratio (P<0.05), while it showed positive correlations with sex, age, TT₃, TT₄ and thyroglobulin (P<0.05). Univariate unconditional Logistic regression analysis revealed that age, weight, BMI, waist circumference, hip circumference, VFA, SFA, HbA_1c, FCP, HOMA-IR, FT₃, SCr, SUA, TC and TG were the influencing factors for NAFLD in T2DM patients. Binary Logistic regression results demonstrated that body weight (OR=0.962), VFA (OR=1.025), SFA (OR=1.006), FT₃ (OR=1.429) and HOMA-IR (OR=1.140) were the influencing risk factors for NAFLD in T2DM patients. Gender (OR=0.342), age (OR=1.073) and free thyroxine (FT₄) (OR=1.140) were influencing factors for thyroid nodules in T2DM patients (P<0.05). ROC curve results showed that the area under the curve (AUC) of BMI, waist circumference, hip circumference, waist-to-hip ratio, VFA and HOMA-IR was 0.704, 0.704, 0.705, 0.629, 0.757, and 0.569, respectively. The optimal cut-off value, sensitivity and specificity of them were listed as follows: BMI (25.37 kg/m², 67.7%, 36.0%), waist circumference (84.5 cm, 67.3%, 36.4%), hip circumference (96.5 cm, 69.4%, 38.9%), waist-to-hip ratio (0.895, 38.8%, 19.1%), VFA (88.4 cm² in female and 99.45 cm² in male, 78.9%, 35.3%), and HOMA-IR (3.08, 64.3%, 49.8%) .

The prevalence of NAFLD and thyroid nodules in T2DM patients significantly increase, but not correlated. Obese T2DM patients, especially those with visceral obesity, are more likely to suffer from NAFLD, thyroid nodules, hyperlipidemia, hyperuricemia and other metabolic diseases. HOMA-IR is a influencing factor for NAFLD in T2DM patients, but it is not a influencing factor for thyroid nodules. BMI, waist circumference, hip circumference and VFA are predictive factors of NAFLD in T2DM patients, and VFA has the highest diagnostic value and HOMA-IR has the lowest value. VFA predicts NAFLD in T2DM patients with the optimal cut-off value of 88.4 cm², which is equal in females and 99.45 cm² in males.

非酒精性脂肪肝（NAFLD）在2型糖尿病（T2DM）患者中患病率明显升高，目前关于T2DM中NAFLD与内脏脂肪面积（VFA）及甲状腺结节的相关研究鲜有报道。

探讨T2DM患者发生NAFLD的相关因素及NAFLD与VFA、甲状腺结节及甲状腺功能的相关性。

回顾性选择2018年1月—2023年4月在广西医科大学第四附属医院（柳州市工人医院）内分泌科住院的T2DM患者为研究对象，依据腹部彩超结果将研究对象分为NAFLD组及非NAFLD组，比较两组的一般资料，VFA、腹部皮下脂肪面积（SFA）、胰岛素功能、甲状腺功能、甲状腺结节患病率、血糖、血脂、肝肾功能水平等指标的差异。依据VFA将研究对象分为内脏性肥胖组（VFA≥100 cm²）和非内脏性肥胖组（VFA<100 cm²），比较两组年龄、性别、NAFLD及甲状腺结节患病率的差异。使用Spearman秩相关分析探讨NAFLD、VFA的相关因素及两者与甲状腺结节的相关性分析，同时探讨甲状腺结节面积大小的相关因素。采用二元Logistic回归分析明确T2DM患者NAFLD及甲状腺结节发生的危险因素。采用受试者工作特征（ROC）曲线评估BMI、腰臀围、腰臀比、VFA、胰岛素抵抗指数（HOMA-IR）对T2DM患者发生NAFLD的预测价值及最佳截断值。

本研究共纳入578例T2DM患者，NAFLD组293例，NAFLD患病率50.69%，非NAFLD组285例。NAFLD组年龄小于非NAFLD组[（57.0±12.8）岁与（59.3±11.6）岁，P<0.05]，NAFLD组体质量、BMI、腰围、臀围、VFA、SFA、糖化血红蛋白（HbA_1c）、空腹胰岛素（FINS）、空腹C肽（FCP）、HOMA-IR、胰岛素分泌指数（HOMA-β）、游离三碘甲状腺原氨酸（FT₃）、血尿酸（SUA）、总胆固醇（TC）、三酰甘油（TG）、C反应蛋白（CRP）均高于非NAFLD组，但其血肌酐（SCr）水平低于非NAFLD组（P<0.05）。内脏性肥胖组251例，非内脏性肥胖组327例，内脏性肥胖组年龄小于非内脏性肥胖组[（55.3±13.4）岁与（60.3±10.8）岁，P<0.05]。内脏性肥胖组患者NAFLD发生率高于非内脏性肥胖组（P<0.05）。内脏性肥胖组与非内脏性肥胖组甲状腺结节患病率（64.94%与59.82%）比较，差异无统计学意义（P>0.05）。Spearman秩相关分析显示：T2DM患者发生NAFLD与体质量、BMI、腰围、臀围、腰臀比、VFA、SFA、HbA_1c、FINS、FCP、HOMA-IR、HOMA-β、总三碘甲状腺原氨酸（TT₃）、FT₃、CRP呈正相关（P<0.05），与年龄呈负相关（P<0.05）。T2DM患者VFA与性别、年龄、身高、体质量、BMI、腰围、臀围、腰臀比、SFA、舒张压、FINS、FCP、HOMA-IR、HOMA-β、TT₃、FT₃、CRP、NAFLD相关（P<0.05）；甲状腺结节面积大小与身高、促甲状腺激素（TSH）、腰臀比呈负相关（P<0.05），与性别、年龄、TT₃、总甲状腺素（TT₄）、甲状腺球蛋白呈正相关（P<0.05）。单因素非条件Logistic回归分析显示，年龄、体质量、BMI、腰围、臀围、VFA、SFA、HbA_1c、FCP、HOMA-IR、FT₃、SCr、SUA、TC、TG是T2DM患者发生NAFLD的影响因素；二元Logistic回归分析显示，体质量（OR=0.962）、VFA（OR=1.025）、SFA（OR=1.006）、FT₃（OR=1.429）、HOMA-IR（OR=1.140）是T2DM发生NAFLD的影响因素；性别（OR=0.342）、年龄（OR=1.073）、游离甲状腺素（FT₄）（OR=1.140）是甲状腺结节的影响因素（P<0.05）。ROC曲线结果显示，各指标预测T2DM患者发生NAFLD的ROC曲线下面积依次为：BMI 0.704、腰围0.704、臀围0.705、腰臀比0.629、VFA 0.757、HOMA-IR 0.569，最佳截断值依次为：BMI 25.37 kg/m²（灵敏度67.7%，特异度36.0%）、腰围84.5 cm（灵敏度67.3%，特异度36.4%）、臀围96.5 cm（灵敏度69.4%，特异度38.9%）、腰臀比0.895（灵敏度38.8%，特异度19.1%）、VFA88.4 cm²（灵敏度78.9%，特异度35.3%）（其中女性88.40 cm²，男性99.45 cm²）、HOMA-IR 3.08（灵敏度64.3%，特异度49.8%）。

T2DM患者NAFLD与甲状腺结节患病率明显升高，但两者之间无明显相关性。肥胖的T2DM患者，尤其内脏性肥胖患者更易罹患NAFLD、甲状腺结节及高脂血症、高尿酸血症等代谢性疾病。HOMA-IR是T2DM患者发生NAFLD的影响因素之一，但不是T2DM患甲状腺结节的影响因素。BMI、腰围、臀围、VFA均可用于预测T2DM患者发生NAFLD，但VFA的预测价值最高，HOMA-IR的价值最低；VFA预测T2DM患者NAFLD最佳截断值为88.4 cm²，女性与总体一致，男性为99.45 cm²。