Subject characteristics
The current study included 490 diabetic patients. A total of 228 patients (46.5%) had thyroid nodules, of which 192 (39.2%) had a solid benign nodule, 30 (6.1%) had a cystic nodule, and 6 (1.2%) had a cancerous nodule. We excluded patients with cystic nodule and cancerous nodule in this study. Overall, 262 patients (53.5%) were without thyroid nodules. In this study, we excluded cystic thyroid nodules and thyroid cancer, only evaluated the largest nodule in patients with multiple nodules. Patients in the thyroid nodules group did not differ from those in the non-thyroid nodules group in terms of age, duration of diabetes, BMI, FBG, P2hBG, HbAlc, TG, TC, HDL-c and LDL-c levels (Table 1).
Comparison of insulin and HOMA-IR in the two groups
A comparison of the FINS and HOMA-IR of patients with and without thyroid nodules is shown in Table 1. Compared with the non-thyroid nodules group, FINS and HOMA-IR levels were elevated in the thyroid nodules group (p <0.05).
Comparison of sex hormones in the two groups
As shown in Table 2, compared with the non-thyroid nodules group,LH levels were significantly higher in the thyroid nodules group (p < 0.05), while TT, SHBG, FSH, P, PRL, E2, DHEA levels were not significantly different (p>0.05).
Comparison of FINS, HOMA-IR, and sex hormones in various thyroid nodules groups
All patients were divided into four groups on the basis of the size of their thyroid nodule (G0: no thyroid nodules,G1: thyroid nodules present but <1.0 cm,G2: thyroid nodules between 1.0 and 2.0 cm,G3: thyroid nodules >2.0cm). Compared with the G0, FINS, HOMA-IR and LH levels were higher in the G1, G2 and G3; Compared with the G1, FINS, HOMA-IR and LH levels were higher in the G3 (p < 0.05, Figure 1),while FSH, TT and E2 levels did not differ (Figure 1) .
Comparison of the incidence of thyroid nodules across levels of FINS, HOMA-IR, LH and TT
All cases were divided into four quartile groups according to FINS, HOMA-IR, LH and TT (Q1 group = 0-25th; Q2 group = 26-50th; Q3 group = 51-75th; Q4 group = 76-100th percentile). Compared with the Q1 group, the incidence of thyroid nodules was higher in the Q4 group of FINS, HOMA-IR and LH (p < 0.05) (Figure 2, A-C). but the incidence of thyroid nodules did not differ in the Q4 group of TT (p > 0.05) (Figure 2, D).
Correlation and regression analysis
Pearson correlations showed that the size of thyroid nodules was positively correlated with FINS, HOMA-IR, LH levels ( r=0.215, p=0.003;r=0.387,p=0.001, r=0.181, p=0.012; respectively ) ( Figure 3) , while size of thyroid nodules was not correlated with TT ( Figure 3), FSH, SHBG, or E2 ( r=0.133, p=0.066; r=0.033,p=0.650; r=0.092,p=0.203;r=0.050, p=0.495, respectively).
We conducted a logistic regression treating the presence of a thyroid nodule as the dependent variable, and age, duration of diabetes, BMI, FBG, HbA1c, FINS, HOMA-IR, TG, LDL-c, HDL-c, TT, LH, FSH and E2 as the independent variables. This analysis showed that FINS, HOMA-IR, LH were independent risk factors for thyroid nodules, and LH were associated with thyroid nodules after controlling for FINS, HOMA-IR (Table 3).