Association and Determinants of Clinical and Subclinical Hypothyroidism in Patients With Diabetic Retinopathy: A Clinic Based Study From North India

Introduction: The association of type 2 diabetes mellitus and thyroid dysfunction is well known.Thyroid dysfunction especially subclinical hypothyroidism has been reported to be a risk factor for sight threatening diabetic retinopathy.Therefore, it is of importance to investigate the determinants of clinical and subclinical hypothyroidism in patients with diabetic retinopathy.This study was aimed to investigate the effect of hypothyroidism on diabetic retinopathy and the determinants of hypothyroidism.Aims: To study the association of hypothyroidism and diabetic retinopathy and its effect on severity of retinopathy in type 2 diabetes and investigate the determinants of hypothyroidism in patients with diabetic retinopathy.Subjects and methods: A cross sectional study conducted on one hundred patients of type 2 diabetes with diabetic retinopathy.They were evaluated for status of diabetes control, thyroid function, lipid profile and retinopathy grade.Those found to have clinical and subclinical hypothyroidism were analyzed for various clinical and biochemical parameters for possible determinants of thyroid dysfunction.Results: There were seventy-four euthyroid patients and eighteen with subclinical hypothyroidism and five with clinical hypothyroidism.Patients with subclinical hypothyroidism had severe form of retinopathy (61.11% versus 32.43%).The odds of having a subclinical hypothyroidism in patients with severe form of diabetic retinopathy was found to be significant (OR 3.23; p=.048 CI=1.10-9.88).High HBA1c was an independent determinant of abnormal thyroid function.Conclusions: About one fourth of type II diabetes patients with retinopathy have thyroid dysfunction.These patients are also likely to have severe form of the retinopathy especially those having subclinical hypothyroidism.Thus, we recommend thyroid function test should be done in all patients with type II diabetes mellitus with retinopathy.Those identified as having subclinical hypothyroidism should be closely followed so as, to detect and prevent vision threatening complications.