Background: Brain natriuretic peptide (BNP) is released from the ventricular myocardium as a reaction to volume expansion and pressure overload. Since the thyroid hormones stimulate the release of BNP, it can be used as an indicator of thyroid failure and also guiding in thyroid control .So; this study was designed to assess the value of measuring serum BNP as a marker for diagnosis and follow up of patients with subclinical and overt hyperthyroidism. Patients and Methods: This is a prospective cohort study for patients with hyperthyroidism. Patients have been enrolled from Endocrinology Outpatient Clinic at Zagazig University Hospitals in the period from December 2018 to October 2020. Results: patients were divided into two major groups, overt hyperthyroidism (group 1) and subclinical hyperthyroidism (group 2).In all cases BNP level over 100 ng/l .Median for BNP in group (1) 671.89 and the median BNP in group (2 ) 318.19 .We noticed a significant elevation of BNP levels in group (1) than group (2) ( p = Keywords words control Brain Naturetic Peptide hyperthyroi