Thyriod：瘦素独立预测促甲状腺激素变化

　　来自西班牙巴塞罗那自治大学的Anna Lucas博士及其团队进行的一项研究发现，甲状腺功能正常的吸烟者，不论男女，体重指数在所有范围内，瘦素均是促甲状腺激素浓度变化的独立预测因子，但非吸烟者中无此相关性。该研究结果在线发表在2013年3月25日的美国《甲状腺》（Thyriod）杂志上。

　　对于甲状腺功能正常的个体，促甲状腺激素水平（TSH）与体重指数（BMI）的关系还不明确。瘦素（LP）调节TSH的分泌，TSH反过来刺激LP分泌。研究旨在评价加泰罗尼亚非住院、甲状腺功能正常的成年人群样本中，瘦素、甲状腺轴和甲状腺自身免疫之间的关系，以及吸烟状况能否影响这种关系。

　　该研究为一项基于人群的横断面研究，包括894例甲状腺功能正常的成年人（390例男性），年龄44.87±15.03岁，BMI26.19±4.61kg/m2,碘供应充足，并且代表加泰罗尼亚居民。分析TSH、游离T4（FT4）、LP、过氧化物酶和/或甲状腺球蛋白抗体（甲状腺自身免疫，TA）、吸烟状况和BMI之间的关系。测量值同样包括血糖和胰岛素，计算HOMA指数。

　　该研究结果表明，在整体群体的单变量分析中，TSH与BMI、LP和HOMA直接相关（P值分别为p=0.039，p<0.001，p=0.010）。在所有男性，TSH与LP直接相关（P=0.004），而在所有女性，TSH与LP（P=0.002）和HOMA（P=0.031）直接相关，但与FT4负相关（P=0.024）。仅在男性吸烟者，TSH与LP（P=0.010）和HOMA（P=0.024）直接相关。在女性吸烟者，TSH与LP直接相关（P=0.004），而在女性非吸烟者，TSH与FT4负相关（P=0.047）。在多元回归多变量分析中，LP（β=0.1187，P=0.03），年龄（β=–0.003410，P=0.013265），吸烟状况（β=–0.24085，P=0.0202）和甲状腺自身免疫（β=0.20652，P=0.0075）是TSH变化的独立预测因子。仅在吸烟者中，LP是TSH变化的有效独立预测因子（β=0.16451，P=0.047），且TA是TSH变化的独立预测因子（β=0.2103，P=0.06）。在男性，TSH的独立预测因子是LP（β=0.1304，P=0.025）和年龄（β=–0.0051，P=0.012），而在女性是LP（β=0.1168，P=0.042），TA（β=0.2591，P=0.001）和FT4（β=–0.1395，P=0.018）。

　　研究同时指出，男性的年龄和吸烟状况，在女性人群中的甲状腺自身免疫阳性和FT4也影响促甲状腺激素变异性。 

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Leptin and thyrotropin relationship is modulated by smoking status in euthyroid subjects.
Background
Thyrotropin concentrations (TSH) and body mass index (BMI) relationship in euthyroid subjects has been demonstrated only in some studies. Leptin (Lp) regulates TSH secretion and TSH stimulates leptin secretion. The main purpose of our study was to assess the relationship between leptin, thyroid axis and thyroid autoimmunity in a representative sample of non-hospitalized euthyroid adult population of Catalonia and if smoking status could influence this relationship.
Methods
This cross-sectional population-based study includes 894 euthyroid adults (390 men), 44.87±15.03 years old, with BMI 26.19±4.61 kg/m2, iodine-sufficient and representative of people leaving in Catalonia. The study analyzes the relationship between TSH, free thyroxine (FT4), Lp, peroxidase and/or thyroglobulin antibodies (thyroid autoimmunity-TA-), smoking status and BMI. Measurements also include glycemia and insulinemia to calculate HOMA index.
Results
In the univariate analysis and in the overall group, TSH correlated directly with BMI, Lp and HOMA (p=0.039, p<0.001, p=0.010, respectively). In all men, TSH correlated directly with Lp (p=0.004) and in all women, directly with Lp (p=0.002) and HOMA (p=0.031) and inversely, with FT4 (p=0.024). Only in smoker (S) men, TSH correlated directly with Lp (p=0.010) and HOMA (p=0.024). In S women, TSH correlated directly with Lp (p=0.004) and in NS women, inversely with FT4 (p=0.047). In the multiple regression multivariate analysis, Lp (β=0.1187, p=0.03), age (β=-0.003410, p=0.013265) smoking status (β=-0.24085; p=0.0202) and thyroid autoimmunity (β=0.20652; p=0.0075) were independent predictors of TSH variations. Leptin was a significant independent predictor of TSH variations only in smokers (β=0.16451; p=0.047). and TA (β=0.2103, p=0.06) were independent predictors of TSH variations. In men, the independent predictors were Lp (β=0.1304, p=0.025) and age (β=-0.0051, p=0.012) and in women, Lp (β=0.1168, p=0.042), TA (β=0.2591, p=0.001) and FT4 (β=-0.1395, p=0.018).
Conclusions
Leptin is an independent predictor factor of thyrotropin concentration variations, only in euthyroid smoker subjects of both sexes at all ranges of body mass index but not in non-smokers. Age, smoking status in men, and thyroid autoimmunity positivity and free T4, in women, also influenced thyrotropin variability.