The Relationship Between Endogenous Testosterone And Lipid Profile In Middle-aged And Elderly Chinese Men

[Background]:For a long time, testosterone was deemed to have adverse effects on lipid profile. Some studies shows that endogenous testosterone is inversely related to the severity of carotid atherosclerosis, as well as the incidence and severity of CHD. Moreover, low testosterone is related to a number of metabolic diseases or disorders, such as insulin resistance, type2diabetes mellitus (T2DM), metabolic syndrome (MetS) and all-cause mortality. Dyslipidemia, one of the main risk factors for hypertension, T2DM, MetS and CHD, is among the most important threats to public health. Hence, the relationship between testosterone and lipid levels needs intensive study. But the relationship between testosterone and lipid profile is complex. Many clinical studies have indicated that free thyroxine as well as TSH are associated with lipid metabolism. However, in the previous studies, the estimates were not adjusted or were only adjusted for the traditional serum lipid confounding factors, such as age, BMI and FBG, and the effects of these hormones on the relationship between testosterone and lipids have not been addressed elsewhere.[Objective]:To evaluate the relationship between serum testosterone level and the lipid profile after adjusting for some traditional confounding factors, free thyroid hormones and thyrotropin in4114middle-aged and elderly Chinese men, which might provide some justification for clinical diagnosis and treatment.[Method]:This population-based cross-sectional study was performed in Ningyang County (Taian, Shandong Province, China), and local registered residents aged40years old and older who lived for at least5years were invited to receive a screening examination. Finally,4114male subjects from the general population were evaluated after exclusion criteria. Past medical history was assessed with a questionnaire and height, weight, waist circumference, hip circumference and blood pressure were measured. Venous blood samples were collected from all the patients between8:00A.M. and10:00A.M. after a minimum12h overnight fast. Serum concentrations of fasting blood glucose (FBG), TC, TG, LDL-C and HDL-C were measured directly with an ARCHITECT ci16200Integrated System (Abbott, Illinois, USA). Serum free triiodothyronine (FT3), free thyroxine (FT4), TSH and TT were measured using electrochemiluminescent procedures (Cobas E601; Roche, Basel, Switzerland). Bivariate and partial correlation analysis, multiple linear regression analysis, one-way analysis of variance, and a general linear model were used to assess the influence of testosterone on the lipid profile. Principal component analysis was used to overcome the multicollinearity among FT3, FT4and TSH and to improve the predictive ability of the model. Chi-squared test was used to compare the prevalence. Additionally, the odds ratios (95%confidence intervals) for hypertriglyceridemia and low HDL-C in relation to testosterone categories were calculated using logistic regression analysis.[Results]:①TT was significantly correlated with TC (r=-0.077, P=0.000), LogTG (r=-0.374, P=0.000), LDL-C (r=-0.069, P=0.000) and HDL-C (r=0.195, P=0.000). TSI was significantly correlated with LogTG (r=-0.122, P=0.000), and HDL-C (r=0.120, P=0.000). The correlations, except for that between LDL-C and TT, remained significant after adjusting for age, BMI, FBG, SBP, factor1, and factor2.②There was a significant linear trend between TT and TC (linear coefficient=-0.094, P=0.012), LogTG (linear coefficient=-0.129, P=0.000), and HDL-C (linear coefficient=0.085, P=0.000).③The prevalence of hypercholesterolemia, high LDL-C and low HDL-C, especially hypertriglyceridemia, decreased significantly in patients who showed increased TT.④The TT and TSI levels in MS group significantly decreased compared to non-MS group. The prevalence of MS in the lowest testosterone group was the highest. Testosterone was significantly correlated to the compents of MS (such as WC, TG, HDL-C, BP and FBG). The testosterone level decreased significantly in patients who showed increased BMI and there was significant difference among BMI categories.⑤The TT and TSI levels in disease group (such as T2DM、CHD and hypertension)significantly decreased compared to non-disease group (P<0.001).[Conclusion]:①TT was significantly correlated with TC, LogTG, LDL-C, and HDL-C. TSI was significantly correlated with LogTG, and HDL-C. The correlations, except for that between LDL-C and TT, remained significant after adjusting for age, BMI, FBG, SBP, factor1, and factor2.②The prevalence of dyslipidemia in patients who showed increased TT, suggesting TT might be a protective factor.③Testosterone was significantly correlated to the compents of MS. The decrease of testosterone level might result in the increase of prevalence of MS.④The TT and TSI levels in disease (such as T2DM、CHD and hypertension) group significantly decreased compared to non-disease group (P<0.001), suggesting that TT might relate to the occurrence and progression of these diseases.