Background: Thalassemia` is an autosomal recessive hereditary chronic hemolytic anaemia caused by a partial or total deficit in the production of β -globin chains that make up the main adult haemoglobin. Patients with the beta-thalassemia major have changes in thyroid function and result from thyroid function tests. The B-cell lymphoma /leukemia11A (BCL11A) gene is mainly located in the human chromosome 2p16.1 region; the BCL11A gene can regulate the expression of fetal haemoglobin.The aim: analysis of the association between beta-thalassemia and the BCL11A gene polymorphism in the Iraqi patient and to evaluate the effect of beta-thalassemia on the thyroid gland through the determination of free thyroxine concentration.

Method: There were 150 participants in this study, split into two primary groups beta-thalassemia patients and healthy individuals. The result is measured using the ELISA for measurement of free thyroxine and polymerase chain reaction techniques for amplification of B-cell lymphoma /leukemia11A (BCL11A) gene polymorphism.

Results: The findings showed a substantial drop in free thyroxine levels in beta-thalassemia patient groups as compared to the control group (P 0.01). The BCL11A gene has three alleles: homozygous CC, heterozygous TC, and homozygous TT. At (431 bais pair and 280 bais pair), (431 bais pair, 280 bais pair, and 195 bais pair), and (431 bais pair, and 195 bais pair), the bands appeared, respectively. The BCL11A rs11886868 gene is affected overall, and research into the causes of thalassemia found a substantial correlation between the BCL11A (rs 11886868) T and C-alleles and thalassemia (P-value = 0.004). The fact that these people have low serum thyroxine (T4) levels highlights the importance of routine screening to assess their endocrine function.

Keywords: BCL11A gene; homozygous; heterozygous; thyroid hormone; β-globin