Association between Subclinical Hypothyroidism and Proliferative Diabetic Retinopathy in Type 2 Diabetic Patients: A Case-Control Study

Abstract

Subclinical hypothyroidism (SCH) is defined as an asymptomatic state characterized by normal serum levels of free thyroxine and elevated serum concentrations of thyrotropin (> 4.0 μ U/ml). The association between SCH and type 2 diabetes has been well established. Proliferative diabetic retinopathy (PDR) that is characterized by neovascularization is a leading cause of visual loss in adults worldwide. However, whether SCH is related to PDR has not been studied. This study thus aimed to evaluate the relationship between SCH and PDR in type 2 diabetes. A total of 371 type 2 diabetic subjects were enrolled: 187 subjects with PDR and 184 subjects without diabetic retinopathy (with HbA1c above 6.5% and at least 10 years of diabetes duration). Subjects with PDR had higher blood pressure, higher serum levels of total cholesterol, low-density lipoprotein cholesterol and thyrotropin, and higher urinary albumin excretion rate. Of the 371 diabetics, 83 subjects (22.4%) were diagnosed as SCH (male 12.1% and female 29.9%). The prevalence of SCH in the PDR group (51/187, 27.3%) was higher than that in the subjects without diabetic retinopathy (32/184, 17.4%). Logistic regression analysis showed that after adjusting for compounding variables, SCH was independently related with PDR ( p = 0.032, adjusted OR = 2.485). These results indicate that type 2 diabetic patients with PDR are at an increased risk of SCH. A routine screening for thyroid function may thus be considered advisable in PDR subjects. This may be helpful in investigating new strategies preventing or treating PDR in clinical practice.

Association of Thyroid-Stimulating Hormone Levels with Microvascular Complications in Type 2 Diabetes Patients

“…Previous studies showed that SCH was associated with DR [17,18], while 2 other studies could not find any relationship between SCH and DR [19,20]. Moreover, it was reported that SCH was an independent risk factor for DN [16,20].…”

“…Furukawa et al [16] considered that SCH was a determinant factor for diabetic nephropathy (DN). Further, 2 reports have shown SCH as a potential factor for increased risk of diabetic retinopathy (DR) [17,18]. However, this relationship between SCH and DR was not found by Ramis et al [19].…”

Estimation of thyroid profile in patients with diabetes mellitus in New Civil Hospital, Surat

“…16 Some of the study recently demonstrated that diabetic patients with subclinical hypothyroidism have more severe retinopathy than euthyroid patients with diabetes. 17 To the best of our knowledge no studies have been done to estimate the prevalence of thyroid dysfunction in DM patients in New Civil Hospital (NCH), Surat. So, the present study was planned to determine prevalence of thyroid dysfunction in DM patients in this institute with the objective to study the thyroid dysfunction in DM for early detection and to provide guideline about treatment strategy accordingly.…”

A study on relationship between severity of diabetic retinopathy and subclinical hypothyroidism

“…13 In the same way, Guang et al in 2010, reported that patients with higher levels of TSH had a significantly higher rate of PDR than patients with lower levels of TSH. 10 Yang et al reported an association between retinopathy and subclinical hypothyroidism, especially sight threatening diabetic retinopathy. They also mentioned that, even euthyroid patients with TSH levels between 2 and <4µIU/ml had a higher rate of sight threatening diabetic retinopathy than those between 0.4 and <2.0µIU/ml (p=0.008).…”