The spectrum of thyroid disorders in adult type 1 diabetes mellitus

Abstract

Background: Thyroid disorders such as goiter, nodules, autoimmune thyroid disease and thyroid dysfunction have rarely been investigated in adult type 1 diabetes mellitus. Our aim was to study the spectrum of thyroid disorders in adult type 1 diabetic subjects and compare them with results obtained from a sample of the general adult population.

Methods: The study population comprised 224 type 1 diabetic and 3481 non-diabetic subjects aged 20-69 years. Thyroid function (TSH, FT3 and FT4) and serum autoantibodies to thyroperoxidase (anti-TPO-Ab) were evaluated from blood samples. Thyroid structure and size were measured by ultrasound.

Results: Type 1 diabetic subjects had a higher risk of known thyroid disease [odds ratio (OR) 1.78, 95% confidence interval (CI) 1.11-2.85], a lower risk of goiter (OR 0.73; 95%-CI 0.54-0.99) and nodules (OR 0.54; 95%-CI 0.35-0.85), and a higher risk of anti-TPO-Ab >200 IU/mL (OR 1.94; 95%-CI 1.28-2.95) compared to the reference population. Furthermore, diabetic subjects had lower serum FT3 levels than the non-diabetic references (adjusted mean 5.00 pmol/L; 95%-CI 4.88-5.12 pmol/L versus 5.27 pmol/L; 95%-CI 5.24-5.30 pmol/L).

Conclusions: Adult type 1 diabetes mellitus is associated with a decreased risk of goiter and nodules and an increased risk of thyroid autoimmunity. A diabetes-related low T3 syndrome may contribute to the differences in thyroid function between type 1 diabetic and non-diabetic subjects.