Influence of type 2 diabetes mellitus combined with subclinical hypothyroidism on diabetic vascular complications

Abstract

Objective To explore the influence of type 2 diabetes mellitus combined with subclinical hypothyroidism on diabetic vascular complications. Methods One hundred and two patients with type 2 diabetes mellitus were selected. The serum free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH), anti-thyroid peroxidase antibody (TPO-Ab), thyroglobulin antibody (TG-Ab) levels were measured by chemiluminescence method. The patients were divided into type 2 diabetes mellitus combined with subclinical hypothyroidism group (47 cases) and type 2 diabetes mellitus with normal thyroid function group (55 cases) according to the thyroid function. The glycated hemoglobin (HbA1c), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triacylglycerol (TG), high-density lipoprotein cholesterol (HDL-C), urea nitrogen, creatinine and albumin levels were measured. The estimated glomerular filtration rate (eGFR) was calculated according to the formula of modification of diet in renal disease (MDRD). The presence of diabetic retinopathy was examined by fundus examination, and the presence of lower limb artery lesions was measured by vascular ultrasound. All indicators were compared between 2 groups. Results There were no statistical differences in age, disease course, HbA1c, body mass index (BMI), TC, TG, HDL-C, LDL-C, incidence of lower limb artery lesions and incidence of diabetic retinopathy between 2 groups (P>0.05). The eGRF in type 2 diabetes mellitus combined with subclinical hypothyroidism group was significantly lower than that in type 2 diabetes mellitus with normal thyroid function group: (83.74±21.55) ml/(min·1.73 m2) vs. (115.02±12.29) ml/(min·1.73 m2), and there was statistical difference (t=4.274, P<0.01). The incidence of diabetic nephropathy in type 2 diabetes mellitus combined with subclinical hypothyroidism group was significantly higher than that in type 2 diabetes mellitus with normal thyroid function group: 48.9% (23/47) vs. 23.6%(13/55), and there was statistical difference (χ2=7.103, P<0.01). Logistic regression analysis showed that subclinical hypothyroidism was a risk factor for diabetic nephropathy (OR=0.524, 95% CI 0.12-0.93, P<0.05), but it was not the risk factor for diabetic retinopathy (OR=0.618, 95% CI 0.19-2.16, P = 0.475) and lower limb artery lesions (OR=0.485, 95% CI 0.32-2.13, P = 0.689). Conclusion Subclinical hypothyroidism in patients with type 2 diabetes mellitus has no obvious effect on lower limb arterial complications and diabetic retinopathy, but may increase the risk of diabetic nephropathy. Key words: Diabetes mellitus, type 2; Hypothyroidism; Diabetic angiopathies; Diabetic nephropathies