Background: Acquired QT prolongation can caused by electrolyte abnormality, myocarditis, cerebrovascular disease, drug intoxication and hormonal disorders such as hypopituitarism, hypothyroidism, and adrenal insufficiency. Case: We describe a 14-year-old boy with hypopituitarism after trans-sphenoidal surgery (TSS) due to suprasellar mass who manifested bradycardia and QT prolongation on electrocardiogram. This subject was complained of blurred vision and bilateral temporal hemianopsia for 1 month. Brain magnetic resonance image (MRI) revealed 3cm sized suprasellar mass and TSS was performed. Germinoma was confirmed by pathology, and he received scheduled chemotherapy including cytoxan. On physical examination, his height and body weight were 143.1cm (- 2.22SDS) and 40.3kg (-1.34 SDS). He grew only 10cm for past 4 years and had no pubertal sign. His pubic hair was Tanner stage I and testicular volumes were less than 4 cc. As the subject showed polyuria and urine was not concentrated during chemotherapy, he started desmopressin 0.1mg bid. Before cocktail test was done, his heart rate was decreased to 35 beat per minute and blood pressure was 90/60 mmHg during sleeping. His heart rate was not increasing and QT interval was prolonged to 580ms on E.K.G, so 0.025mg/kg/hr of isoproterenol, beta agonist, was started. Thyroidal and pituitary function test were performed at that time, resulting in panhypopituitarism. Thyroid stimulating hormone and free T4 were 0.15μIU/mL and 0.67 ng/dL, respectively. The stimulated ACTH was 35.2pg/ml despite cortisol was 1ng/dL. After hormone replacement including hydrocortisone 5mg three times (10mg/m2/d) and levothyroxine 50mcg per day, isoproterenol tapered off for five days and QT interval was normalized. Ten days after multiple hormone replacement, hormone levels were also corrected well and his vital sign and E.K.G were also stable. Conclusion: This case highlights that hormonal disorders should be considered as a cause of arrhythmia or prolongation of QT intervals and this can be prevent and cured by appropriate hormone replacement therapy.