Autoimmune thyroid disease in Libyan children and young adults with type 1 diabetes mellitus

Diabetes mellitus is a common autoimmune endocrine disorder associated with organ-specific autoantibodies which are frequently detected at the time of diagnosis. Some of these antibodies are specific to the pancreas (GAD, IA2, ICA) while others are related to different autoimmune diseases.

To define the prevalence of thyroid autoimmune disease in Libyan patients with type 1 diabetes mellitus (T1DM) since no similar studies have been performed in Libya.

Blood samples were collected from 218 patients with T1DM who are followed by the Pediatric Department, Tripoli Medical Center, Libya. All sera were analyzed in Italy (Laboratory of Immunopathology and Allergy, Udine). The patients were composed of 123 females (56.4%) and 95 males (43.6%), mean age 12.2 ± 4.6 years (range 2.1-24.5 years), mean duration of diabetes 4.7 ± 4.0 years (range 0.1-17.5 years). Sera were tested for anti-thyroperoxidase (TPO) and anti-thyroglobulin antibodies (TG). TSH and FT4 concentrations were measured in all subjects. GAD, IA-2 was also measured.

Of the diabetic children, 23.4% were positive for anti-microsomal peroxidase antibodies (TPO-Ab) and 7.8% for antithyroglobulin antibodies (TG-Ab); whereas 6.9% of the patients were positive for both TPO-Ab and TG-Ab. Of the T1DM patients who were positive for TPO-Ab, 66.6% were females. The majority (57%) of the patients who were positive for TPO had diabetes for longer than 5 years. Five patients (2.3%) had evidence of subclinical hypothyroidism whereas two patients (0.9%) had overt hypothyroidism. Two patients had subclinical hyperthyroidism and two (0.9%) had overt hyperthyroidism. Interestingly, 16.2% of patients were positive for both thyroid and pancreatic antibodies.

The prevalence of autoimmune thyroid disease in type 1 diabetic patients is higher than in the general population. A routine screening strategy should be implemented with the determination of anti-thyroid antibodies and TSH in type 1 diabetic patients, particularly in girls, and in patients with diabetes of more than 5 years duration. Patients who have positive TPO antibodies may need the assessment of thyroid function at shorter intervals.