BACKGROUND: Most characteristics and common signs and symptoms of hyperthyroidism are the effects of thyroid  hormones  on  the heart and cardiovascular system. With the advent of echocardiography, characterizing the effects of  hyperthyroidism on the heart has been described mainly for overt hyperthyroidism. Data on subclinical hyperthyroidism  are still conflicting.
OBJECTIVE: To describe and compare the cardiac morphology and function of Filipino patients with uncontrolled overt and subclinical hyperthyroidism through echocardiogram, admitted at De La Salle University Medical Center (DLSUMC) for a period  of  five years and six months. 
METHODOLOGY: This is a retrospective descriptive study that utilized review of medical records. Seventy-five  hyperthyroid patients were included; 56%  with overt hyperthyroidism and 44% with subclinical hyperthyroidism. Cardiac morphology and systolic and diastolic functions were determined in the population and compared  between overt and subclinical hyperthyroidism using 2-dimensional echocardiogram.  
RESULTS: Cardiac morphology was slightly  compromised due to slight thickening of interventricular septum (IVSTd) and left ventricular posterior wall thickness at diastole (LVPWTd). There was also an increase in left ventricular mass (LVM), more pronounced in overt hyperthyroidism. Systolic function parameters such as fractional shortening (FS) and ejection fraction (EF) were normal. Impaired left ventricular myocardial relaxation manifested as low early mitral peak flow velocity, low E/A ratio and prolonged isovolumetricrelaxation time (IVRT) was observed in most patients, particularly in overt hyperthyroidism.
CONCLUSION: Abnormalities noted were comparable between the two groups of hyperthyroidism. With cardiac  parameters affected even in subclinical hyperthyroidism, treatment might be indicated regardless if hyperthyroidism is  overt or subclinical.