Changes of serum thyroid hormone in elder patients with type 2 diabetes mellitus and its clinical significance

Abstract

Objective To investigate the changes of serum thyroid hormone in elder patients with type 2 diabetes mellitus and its chnical significance.Methods A total of 436 elder patients with type 2 diabetes mellitus (elder diabetes mellitus group) and 312 cases without diabetes mellitus (control group)were underwent thyroid ultrasound.For all of the patients,clinical data including fasting plasma glucose (FPG),hemoglobin A1c (HbA1c),serum lipid were tested.Serum thyroid hormone such as total triio dothyronine (TT3),total thyroxine (TT4),free triio dothyronine (FT3),free thyroxine (FT4),thyrotrophin (TSH),antithyroglobulin antibody (TGAb) and anti-thyroid peroxidase antibody (TPOAb) were measured simultaneously.The patients were divided into 3 groups according to the level of HbA1c:HbA1c ＜ 7.5％ group(132 cases),HbA1c 7.5％-9.0％ group(211 cases) and HbA1c ＞ 9.0％ group(93 cases).And they were also divided into 4 groups according to the level of duration:duration ≤ 1 year group (65 cases),1 year ＜ duration ≤ 5 years group(133 cases),5 years ＜ duration≤ 10 years group(195 cases) and duration ＞ 10 years group (43 cases).The levels of thyroid function and thyroid ultrasound were compared among different groups.Results The incidence of abnormal structure of thyroid was 19.7％ (86/436) and the incidence of hypothyroidism and sub-clinical hypothyroidism was higher than the incidence of hyperthyroidism and sub-clinical hyperthyroidism [14.4％ (63/436) vs.5.3％ (23/436)] in elder diabetes mellitus group,and there was significant difference(P＜ 0.05).Compared with that in control group,TT3,FT3 was decreased [(1.27 ± 0.20) nmol/L vs.(1.60 ± 0.34) nmol/L,(3.71 ± 0.49) pmol/L vs.(4.45 ± 0.62)pmol/L],TGAb,TPOAb and thyroid gland volume was increased [(74.73 ±41.25) kU/L vs.(40.05 ± 18.28) kU/L,(87.46 ± 36.81) kU/L vs.(42.39 ± 20.84) kU/L,(17.1 ± 3.0) ml vs.(13.7 ± 2.5) ml],the ratio of thyroid swelling and thyroid nodule was increased [17.66％(77/436) vs.4.17％(13/312),59.86％ (261/436) vs.29.49％ (92/312)],and there was significant difference (P ＜ 0.05).While the levels of HbA 1c increased,the levels of TT3 and TSH decreased simultaneously.The level of FT3 in HbA1c ＞ 9.0％ group was lower than that in HbA1c ＜ 7.5 ％ group and HbA1c 7.5 ％-9.0％ group [(3.46 ± 0.39) pmol/L vs.(3.73 ± 0.47),(3.75 ± 0.49) pmol/L] (P ＜ 0.05),the ratio of thyroid swelling,thyroid nodule and abnormal thyroid echo in HbA1c ＞ 9.0％ group was higher than that in HbA1c ＜ 7.5％ group and HbA1c 7.5％-9.0％ group [36.6％ (34/93) vs.11.4％ (15/132),13.3％ (28/211);90.3％ (84/93) vs.50.0％ (66/132),52.6％ (111/211) ;45.2％(42/93) vs.12.9％(17/132),15.2％(32/211)],and there was significant difference (P ＜0.05).When the duration of diabetes increased,the levels of TT3,FT3 decreased and the levels of TSH,TGAb increased simultaneously.Conclusions It is common that elder patients with type 2 diabetes mellitus always follow with thyroid dysfunction,which should be checked out and followed up.The levels of thyroid function are important for assessing the glucose metabolism in elder patients with type 2 diabetes mellitus. Key words: Aged;  Diabetes mellitus;  Thyroid hormones;  Ultrasonography