Clinical Observation Of Thyroid Hormones Levels In Patients With Type 2 Diabetes And Analysis On Relative Factors

ObjectiveTo evaluate the levels of serum thyroid hormones and thyrotrophin among type 2 diabetic patients without thyroxin, methimazole or propylthiouracil therapy,and analyse the diabetic factors related with states of thyroid function. And then correlate different diabetic condition and serum thyroid hormone levels among type 2 diabetic patients for reference to clinical diagnosis and treatment.MethodsThree hundred and sixty-five type 2 diabetic subjects were consecutively recruited in this cross-sectional study. Clinical data was collected, such as age, sex, course, complications, current medication types of hypoglycemic agents. Biochemical indicators such as fasting plasma glucose(FPG), glycosylated hemoglobin Alc(HbAlc), total cholesterol(TC), triglyceride(TG), low density lipoprotein cholesterol(LDL-C) and high density lipoprotein cholesterol(HDL-C) were retrieved from biochemistry laboratory database. And serum free triiodothyronine(FT3), free thyroxine(FT4) and thyrotrophin (TSH) were tested for analyzing thyroid function states of type 2 diabetic patients and relative factors. Then group according to different diabetic condition for further exploring on relative factors that affecting levels of serum thyroid hormones. Statistical analysis was performed using SPSS 20.0 software, with logistic regression for analyzing factors leading to thyroid dysfunction among type 2 diabetic patients, and we conducted spearman correlation analysis and multiple linear regression using FT3, FT4 and TSH as an argument, respectively.Results1. General information of patients:(1) Compared with the euthyroidism group, the thyroid dysfunction group has a significantly higher FPG, HbAlc, TSH, number of complications and a significantly lower FT3, and the difference was statistically significant (P<0.05). There were no significantly differences between FT4 and lipid index, as well as age, course between two groups (P all<0.05). (2) There are 81 cases of thyroid dysfunction (22.19%) among type 2 diabetic patients. The incidence of low T3 and subclinical hypothyroidism (8.2%,7.9%, respectively) were both significantly higher than others (P both<0.01). And the incidence of thyroid dysfunction in female patients was higher than that in male patients, but the difference was not statistically significant (P= 0.05).2.Logistic regression:With thyroid dysfunction as a dependent variable, the variables (sex, FPG, TG, HDL, metformin treatment) were selected by stepwise regression method. Thyroid dysfunction among type 2 diabetic patients without thyroxin, methimazole or propylthiouracil therapy showed a positive correlation with FPG (OR= 1.168, P<0.001) and a negative correlation with TG, HDL and metformin treatment (OR=0.503,0.227> 0.536, Pall<0.05).3. Comparison of thyroid hormone indexes among type 2 diabetic patients:(1) Sex and thyroid hormones:Female patients had a significant higher TSH than male patients (P<0.01); The differences of levels of FT3 and FT4 between male and female patients were not statistically significant. (2) HbAlc and thyroid hormones:With the increase of HbAlc, the level of FT3 was gradually decreased, while TSH and FT4 levels were increased, but there was no significant difference between the three groups on TSH and FT3 (P>0.05). (3) Age and thyroid hormones:FT3, TSH decreased and FT4 increased as age increased, and the differences were significant (P <0.01). (4) Course and thyroid hormones:there were no differences among different groups on FT4 and TSH. (5) Complication and thyroid hormones:Serum FT3 level of group with more than or equal to 3 complications was below than group with 1 or 2 complications and 0 complication, but the difference was not statistically significant. (6) Metformin and thyroid hormones:Comparison between metformin group and non-metformin group [M(+)/O(+)group VS. M(-)/O(+)group, M(+)/O(-)group VS. M(-)/O(-)group], the level of FT3 increased and FT4 decreased. Compared with the M (-)/O (-) group, the TSH levels in the other 3 groups were decreased in different degrees. But all the differences were not statistically significant (P>0.05).4. Spearman correlation analysis and multiple linear regression:(1) FT3 had a negative correlation with age, course and number of complication (r=-0.329.-0.124.-0.108, P all< 0.05), while FT4 had a positive correlation with age, course, FPG, HbAlc (r= 0.170.0.106.0.162.0.197, P all< 0.05); There was a negative correlation between TSH and age(r=-0.113, P= 0.029), as well as a positive correlation between TSH and HDL(r= 0.106, P= 0.041). There were no correlativity between FT3. FT4. TSH and TG、LDL (P all>0.05). (2) Multiple stepwise regression analysis showed that age was the independent factor that affected FT3 (OR=-0.022, P<0.001); age, FPG, TG, LDL were all independently associated with FT4(OR=0.038、0.192、—0.383. —0.973, P均< 0.05); HbAlc was the independent factor that affected TSH (OR=0.189, P=0.024), with FT3, FT4 and TSH as dependent variable, respectively.Conclusion1. The incidence of thyroid dysfunction in type 2 diabetic patients without thyroxin, methimazole or propylthiouracil therapy was 22.19%, with mainly manifested as low T3 and subclinical hypothyroidism, and a decrease of FT3 and elevated TSH level. FPG was the risk factors of thyroid dysfunction, while metformin may be the protective factor of thyroid dysfunction.2. The levels of serum thyroid hormones in patients with type 2 diabetes were closely related to the age, sex, blood glucose, course of disease, complications, blood lipid and hypoglycemic agents. Due to the metabolic abnormality, changes of diabetic condition could affect the levels of serum thyroid hormones, therefore screening and follow-up are important. Thyroid hormone levels had a certain clinical significance for estimating Type 2 diabetic condition.