Hyperthyroidism may be associated with several haematological disorders, including an increase in haemoglobin A2 level. We report the case of haemoglobin study in a 29-years old man of Mediterranean origin presenting microcytosis. Results showed a slight increase in haemoglobin A2 level, suggestive of a beta-thalassemia trait, which was finally related to the existence of a recently diagnosed Grave's disease.
Keywords: haemoglobin A2; hyperthyroidism; β-thalassemia trait.