Prevalence of thyroid dysfunction in patients with type 2 diabetes mellitus

Abstract

Diabetes mellitus (DM) and thyroid dysfunction (TD) are two common endocrine disorders. The unrecognized subclinical TD may adversely affect metabolic control and increase cardiovascular risk. Our aim was to investigate the prevalence of TD in patients with type 2 diabetes mellitus in an observational cross-sectional study. Clinical and laboratory evaluation was performed to 205 consecutive outpatients at Endocrinology Diabetes and Nutrition Center in Concepcion City, Tucuman, Argentina. Thyroid dysfunction was classified as clinical hypothyroidism with TSH > 4.20 mUI/ml and FT4 < 0.93 ng/dl, subclinical hypothyroidism with TSH > 4.20 mUI/ml and free T4 0.93 to 1.70 ng/dl. Subclinical hyperthyroidism was considered with TSH < 0.27 mUI/ml and free T4 was in normal range (0.93 to 1.70 ng/dl); and clinical hyperthyroidism with TSH < 0.27 mUI/ml and free T4 >1.70 mUI/ml. Autoimmunity was diagnosed with anti-TPO > 34 IU/ml. TD prevalence in type 2 diabetic patients was 48% (n = 92). In subjects who denied prior TD, the prevalence was 40% (n = 37), 15 with subclinical hypothyroidism (45%). In the whole study population prevalence of subclinical hypothyroidism was 8%. Globally, subclinical DT prevalence was 9% (n = 17) and anti-TPO 13% (n = 25). Early detection of thyroid dysfunction in patients with type 2 diabetes mellitus should be performed routinely, given the high rate of newly diagnosed cases, and increased cardiovascular risk associated with undiagnosed thyroid dysfunction.