Hypothyroidism in Patients With Type 1 Diabetes

Type 1 diabetes is an organ-specific autoimmune disease characterized by the selective destruction of pancreatic β-cells. The histopathology of type 1 diabetes is defined by a decreased β-cell mass infiltration of mononuclear cells into the islets of Langerhans , this lesion was later called 'insulitis', and it is the hallmark of the disease .

Insulitis was observed in 70% of patients with acute onset type 1 diabetes and concluded that this disease was caused by a β-cell-specific autoimmune process .

Furthermore, in a study demonstrated cellular autoimmunity in patients with type 1 diabetes using the leukocyte migration test and speculated that cellular hypersensitivity was the counter part of lymphocytic infiltration in islets . Therefore, it is speculated that cell-mediated immunity could play an important part in the pathogenesis of type 1 diabetes .

As a view suggesting that type 1 diabetes is an autoimmune disease, there is some evidence that type 1 diabetes is often complicated with other autoimmune diseases or that anti-islet antibodies precede the clinical onset of the disease.

So, it is found that type 1 diabetes is frequently associated with other organ-specific autoimmune diseases, including hypothyroidism , pernicious anaemia, and idiopathic Addison's disease .The most common coexisting organ autoimmune disease is hypothyroidism (>90%), the prevalence of anti-thyroid autoantibodies in children with type 1 diabetes at disease onset is about 20% .

It is generally accepted that is a T cell-mediated autoimmune disease and that circulating autoantibodies to various islet cell antigens are induced following the destruction of pancreatic β cells .

Furthermore, it is reported that the prevalence of anti-thyroid antibodies increases with increasing age and that the presence of anti-thyroid antibodies at diagnosis of type 1 diabetes predicts the development of future thyroid disease as patients with antithyroid antibodies are 18 times more likely to develop thyroid disease than patients without anti-thyroid antibodies .

Therefore, for early detection of hypothyroidism in children with type 1 diabetes, it is suggested to measure anti-thyroid antibodies and thyroid stimulating hormone at disease onset and in yearly intervals after the age of 12 yr. Furthermore, the International Society for Pediatric and Adolescent Diabetes Consensus Clinical Guidelines recommend the screening of thyroid function by analysing circulating thyroid stimulating hormone at the diagnosis of diabetes and, thereafter every 2nd yr. in asymptomatic individuals without goitre and more frequent if goitre present .