Background: Thalassemia is the most common hereditary anemia and beta thalassemia major is its most severe form. ENDOCRINE abnormalities in thalassemia major are common disturbing complications that need prompt management. The purpose of this study was to determine the ENDOCRINE disorders and bone mineral density in patients with major b-thalassemia in Qazvin, Iran.Methods: In this cross-sectional study, 77 patients with b-thalassemia major (15-36 years old) were enrolled. Physical examination, laboratory tests, bone radiography and bone density measurements were performed. Then, the data were analyzed.Results: Forty patients were males. The mean age was 21.26±4.53 years old. The mean BMI was 20.15±2.79 kg/m2. Impaired puberty, short stature, hypothyroidism, diabetes mellitus, IGT, hypoparathyroidism, vitamin D deficiency and vitamin D insufficiency were observed in 46.8%, 33.8%, 18.2%, 16.9%, 13%, 7.8%, 45.5% and 24.7% of patients, respectively. Nearly 80% of patients had low bone mineral density. Bone mineral density was significantly associated with hypogonadism (p=0.001), short stature (p=0.026), hypoparathyroidism (p=0.031), hypothyroidism (p=0.048), diabetes mellitus (p=0.002) and vitamin D deficiency (p<0.001).Conclusion: Impaired puberty and short stature were the most common ENDOCRINE complications in our population. Low bone density (osteopenia, osteoporosis) is significantly different in b-thalassemic patients with and without ENDOCRINE complications.