[Erythrocyte abnormalities in thyroid dysfunction].

Background: Erythrocyte abnormalities are frequently associated with thyroid dysfunction. However, they are rarely investigated and related to the thyroid.

Aim: This study was aimed to determine the nature and frequency of erythrocyte abnormalities in thyroid disease and look for their evolution after thyroid function restoration.

Methods: This retrospective study included 412 patients with peripheral thyroid disease; hyperthyroidism (n=235) or hypothyroidism (n=177). Hyperthyroidism was considered for TSH<0.10 ÌUI/ml and hypothyroidism for TSH>5.0 ÌUI/ml. Anemia was defined by hemoglobin level<13 g/dl in men and <12 g/dl in women, microcytosis by mean corpuscular volume (MCV)<80 fl, macrocytosis by MCV>98 fl, and hypochromia by mean corpuscular hemoglobin (MCH)<25 pg. Restoration of euthyroid state was considered in patients with normal TSH levels for at least 3 months.

Results: Anaemia was observed in 40.9% of patients with hyperthyroidism and 57.1% of patients with hypothyroidism. Among these, normocytic or macrocytic anaemia was present in 46.3% of cases. Whereas, microcytosis, with or without anaemia, was noted in 87.7% of patients with hyperthyroidism. FT4 was positively correlated with the number of red blood cells and haemoglobin, and inversely correlated with MCV and MCH. After restoration of euthyroid state, most erythrocyte abnormalities were corrected.

Conclusion: Thyroid diseases are frequently associated with erythrocyte abnormalities, including normocytic anaemia in hypothyroidism and microcytosis in hyperthyroidism. These abnormalities should be investigated and corrected. Their presence could steer towards subclinical thyroid dysfunction, allowing its early management.