Supplementary Material for: The Fatty Liver Index, the Strongest Risk Factor for Low Testosterone Level

Introduction: The study aimed to determine if hepatic steatosis assessed by Fatty Liver Index (FLI) was an independent risk factor for male testosterone insufficiencylow testosterone level and whether the FLI was the strongest risk factor for testosterone insufficiencylow testosterone level in two different age groups. Methods: Two cross-sectional studies were performed. A total of 3443 male participants (aged 46-75) were recruited into study A (part of lONgitudinal study (REACTION)). Then a total of 267 male participants (aged 25-45) were recruited into study B. Serum TT and sex hormone-binding globulin (SHBG) levels, indicators for assessing hepatic steatosis were measured. The Pearson correlation and regression analysis were performed to investigate the risk factors for testosterone insufficiencylow testosterone level. Results: The FLI had the strongest negative correlation with serum testosterone in the study A (r=-0.436) and B (r=-0.542). Compared with patients with a FLI lower than 30, the risk for testosterone insufficiencylow testosterone level increased by 3.48–fold in subjects with a FLI higher than 60 adjusted for potential risk factors in study A. In study B, the OR of testosterone insufficiencylow testosterone level in patients with potential hepatic steatosis was 4.26 (1.57-11.60) after adjusted for age and HOMA-IR, and 0.59 (0.14-2.60) after adjusted for age, HOMA-IR, waist circumference, body mass index, and SHBG. Conclusions: FLI, was the strongest risk factor for male testosterone insufficiencylow testosterone level independent of insulin resistance in a male populations of different ages, however the association can be modulated by SHBG levels in the young.

引言：本研究旨在明确通过脂肪变性指数（Fatty Liver Index, FLI）评估的肝脂肪变性是否为男性睾酮不足（低睾酮水平）的独立危险因素，并探究FLI是否为两个不同年龄组男性人群中睾酮不足（低睾酮水平）的最强危险因素。
方法：本研究开展两项横断面研究。研究A共招募3443名男性参与者，年龄范围为46~75岁，其为纵向研究REACTION的一部分。研究B共招募267名男性参与者，年龄范围为25~45岁。检测受试者血清总睾酮（TT）、性激素结合球蛋白（Sex Hormone-Binding Globulin, SHBG）水平及肝脂肪变性评估相关指标。采用皮尔逊相关分析与回归分析，探究男性睾酮不足（低睾酮水平）的危险因素。
结果：研究A中，FLI与血清睾酮呈最强负相关（r=-0.436）；研究B中该相关系数为-0.542。在研究A中，校正潜在混杂危险因素后，与FLI＜30的男性受试者相比，FLI＞60的受试者发生睾酮不足（低睾酮水平）的风险升高3.48倍。在研究B中，校正年龄与稳态模型评估胰岛素抵抗指数（HOMA-IR）后，合并肝脂肪变性的男性受试者发生睾酮不足（低睾酮水平）的比值比（OR）为4.26（1.57~11.60）；进一步校正年龄、HOMA-IR、腰围、体质量指数及SHBG后，该OR值为0.59（0.14~2.60）。
结论：在不同年龄的男性人群中，FLI是独立于胰岛素抵抗的男性睾酮不足（低睾酮水平）的最强危险因素，但在年轻男性人群中，该关联可受SHBG水平调控。