Introduction:
Autoimmune diseases concomitant with diabetes may complicate the treatment and adversely affect the prognosis. The most common is Hashimoto’s disease (HD). We compared diabetes control and prevalence of chronic complications in type 1 diabetes patients differing in the coexistence of HD.

Material and methods:
Medical records of 188 type 1 diabetics were analysed. Hashimoto’s disease was diagnosed based on medical history, as well as determination of the levels of thyroid peroxidase antibodies, hormones and ultrasound exa¬mination. Statistical analysis was performed using Statistica 10PL.

Results:
HD was diagnosed in 43 patients (23%). The mean HbA_1c was 8.8 ±1.5% in the group with HD, and 9 ±1.6% in the group without HD (ns). The prevalence of diabetes complications was similar in both groups: ischae¬mic heart disease was diagnosed in 19% of patients with HD and 19% without HD, cerebral vascular insufficiency – 8% and 7%, peripheral neuropathy – 14% and 12%, sensory polyneuropathy – 47% and 46%, diabetic foot – 7% and 8%, Charcot osteoarthropathy – 7% and 2%, cardiovascular neuropathy – 21% and 28%, neuropathy of the gastrointestinal tract – 5% and 6%, nephropathy – 12% and 19%, retinopathy – 42% and 43%, and cataract in 28% and 19%, respectively. Impaired hypoglycaemia perception was rarer in the group with HD: 9% vs. 25% (p ≈0.04).

Conclusions:
Hashimoto’s disease does not significantly affect the level of type 1 diabetes control or the development of its complications. Only autonomic neuropathy in the form of impaired awareness of hypoglycaemia is rarer in patients with that thyroiditis.