Chronic unexplained anaemia in isolated autoimmune thyroid disease or associated with autoimmune related disorders

Objective The prevalence of chronic unexplained anaemia was analysed in patients with autoimmune thyroid disease (ATD). Design The presence of chronic unexplained anaemia, defined as anaemia not related to evident or occult bleeding and/or to erythropoietic disorders, was retrospectively assessed and compared in patients with nonautoimmune thyroid disease (NATD) and in patients with ATD. Subjects and measurements Biochemical and morphological parameters of anaemia were investigated and characterized in 1643 consecutive Caucasian outpatients with thyroid disease. In 991 patients, thyroid disease had a nonautoimmune origin. ATD was diagnosed in 652 patients (71 had Graves' disease and 581 had Hashimoto's thyroiditis and its variants). In 145 patients ATD was associated with other autoimmune disorders. Results The presence of chronic unexplained anaemia was diagnosed in 123 patients (7.5%). Forty-eight had a thalassaemic trait, representing 2.9% of the whole sample. A true chronic unexplained anaemia was recorded in 75/1643 (4.6%). The occurrence of unexplained anaemia was similar in patients with NATD (1.9%) and in those with isolated ATD (2.96%; P = NS) but increased in patients with ATD and autoimmune related disorders (ARD) compared to patients with isolated ATD and/or with NATD (28.3%; both P < 0.0001; RR = 9.56 and 14.75, respectively). Chronic unexplained anaemia was virtually absent in hyperthyroid patients and was more prevalent in hypothyroid than in euthyroid patients with ATD (P = 0.0047; RR = 2.104). Conclusions These results indicate that the increased frequency of chronic anaemia in patients with ATD is essentially due to the presence of concomitant autoimmune gastrointestinal diseases.