Anti-GAD-Positive Patients with Type 1
Diabetes Mellitus Have Higher Prevalence of Autoimmune Thyroiditis than
Anti-GAD-Negative Patients with Type 1 and Type 2 Diabetes Mellitus
H. BÁROVÁ1,2, J. PERUŠIČOVÁ1,2, M. HILL2,
I. ŠTERZL2, K. VONDRA2,
Z. MAŠEK2
1Center of Diabetology, Third Department of Medicine, General
Hospital, First Faculty of Medicine, Charles University and 2Institute
of Endocrinology, Prague, Czech Republic
Received May 22, 2003
Accepted July 21, 2003
Summary
The aim of our study was to evaluate antibodies against thyroglobulin
(anti-TG) and thyroid peroxidase (anti-TPO) – markers of autoimmune
thyroiditis – in several groups of adult patients with type 1 and type 2
diabetes mellitus (DM). We were particularly interested whether the
presence of thyroid antibodies is related to the positivity of glutamic
acid decarboxylase antibodies (anti-GAD). We found elevated anti-GAD in 46
% (97/210) patients with type 1 DM. All patients with type 2 diabetes were
anti-GAD-negative. At least one thyroid antibody (anti-TG and/or anti-TPO)
was found in 30 % (62/210) patients with type 1 DM and 27 % (22/83) type 2
diabetes patients. The patients with type 1 DM were further grouped
according to their anti-GAD status. The anti-GAD-positive patients had a
higher prevalence of anti-TG antibodies than the anti-GAD-negative
patients (25 % vs. 12 %, p=0.03) as well as anti-TPO antibodies (32 % vs.
12 %, p<0.001). At least one thyroid antibody was detected in 39 % (38/97)
of anti-GAD-positive but only in 21 % (24/113) of anti-GAD-negative
patients with type 1 DM (p=0.006). No significant difference in the
frequency of thyroid antibodies was found between anti-GAD-negative
patients with type 1 and type 2 DM (21 % vs. 27 %, p=0.4). The groups with
or without thyroid antibodies in both type 1 and type 2 diabetic patients
did not differ in actual age, the age at diabetes onset, duration of
diabetes, body mass index or HbA1c level. Patients with elevated thyroid
antibodies had significantly higher levels of TSH than those without
thyroid antibodies (1.86 vs. 3.22 mIU/l, p=0.04 in type 1 DM; 2.06 vs.
4.89 mIU/l, p=0.003 in type 2 DM). We conclude that there is a higher
frequency of thyroid-specific antibodies in anti-GAD-positive adult
patients with type 1 DM than in anti-GAD-negative patients or in patients
with type 2 DM. Patients with or without thyroid antibodies do not differ
in age, DM onset and duration, BMI or HbA1c. Thyroid antibodies-positive
patients have higher levels of thyroid stimulating hormone (TSH).
Key words
Diabetes mellitus • Thyroid antibody • Autoimmune thyroiditis • Glutamic
acid decarboxylase antibody
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