Endocrine Abstracts

Introduction: Type 1 diabetes mellitus (T1DM) is the result of the autoimmune destruction of beta-cells of the endocrine pancreas, leading to absolute insulin deficiency. The process of this autoimmune destruction occurs in genetically susceptible individuals with positive relevant autoantibodies. T1DM may be associated with other autoimmune diseases (AD) such as autoimmune thyroid disorders (AITD).

Patients and methods: It is a descriptive retrospective study. We collected data from 113 patients diagnosed with AITD associated with another AD over 18 years. The present study reports the association between T1DM and AITD.

Results: T1DM was diagnosed in 41 patients (31.53%) which consisted of 25 women and 16 men. The mean age upon discovery of the T1DM was 30.49 years. The T1DM was associated with an overt hypothyroidism in 18 patients, a subclinical hypothyroidism in 1 patient, an autoimmune thyropathy in euthyroid phase in 7 patients, an overt hyperthyroidism in 14 patients and a subclinical hyperthyroidism in 1 patient. It was affiliated with Hashimoto’s disease in 26 cases (63.4% of cases) and with Graves’ disease in 15 cases (36.6% of cases). The T1DM preceded the diagnosis of the thyroid disorder in 24 cases with a mean period of 69 months between and succeeded the latter in 6 cases within a mean period of 40 months. In 11 cases, both diagnoses were concomitant.

Discussion and Conclusion: T1DM is the most frequent AD associated with AITD. Their prevalence is 2 to 3 times higher in the T1DM population than that of the general population. As a matter of fact, 6.6% out of 10% of healthy adults have positive thyroid antibodies compared to 20% out of 40% of T1DM adults. According to Barker, T1DM is associated with Hashimoto’s disease in 14-28% of cases. In other studies, it is associated with Graves’ disease in 0.5-7% of cases. Several studies demonstrated that AITD was more frequent in diabetic women than men, which could be explained by higher prevalence of AITD in women. Serum TSH assay is recommended upon discovery of diabetes in patients with hypothyroid or hyperthyroid symptoms, then every 1-2 years as follow up. Our results consistent with that of the literature showed the high prevalence of the T1DM in patients with AITD, and thus the necessity of regular screening in these patients.

References: Barker JM. Clinical review: type 1 diabetes-associated autoimmunity: natural history, genetic associations, and screening. Journal of Clinical Endocrinology and Metabolism. 2006; 91(4): 1210–1217.