Endocrine Abstracts

Introduction: Isolated adrenocorticotropic hormone (ACTH) deficiency (IAD) is a rare disease, which is characterized by secondary adrenal insufficiency with low cortisol production, and normal secretion of pituitary hormones other than ACTH. Although it is known that QT prolongation is sometimes observed in patients with IAD, reports on IAD in which the QT interval was sufficiently prolonged to cause Torsades de Pointes (TdP) are rare. We described the case of a patient with IAD and arrhythmia with prolongation of QT interval.

Case report: A 48-year-old woman was rushed to the hospital with fever and syncope. She had similar episodes at the age of 39 years. The electrocardiogram (ECG) showed prolongation of QT interval (QTc 0.64 sec). The ECG monitoring registered polymorphic VT (TdP); thus, she received basic life support. However, due to recurrent TdP, we performed Implantable Cardioverter Defibrillator (ICD) implantation. She initially had two ICD operations for fever, and subsequently for ventricular fibrillation. Echocardiography showed normal cardiac size and left ventricular function. In addition, she had hypotension, hyponatremia, seizure, and hypoglycemia. Therefore, we suspected adrenal insufficiency. Endocrinological examination showed low plasma ACTH (<2.0 pg/ml) and cortisol (1.16 μg/dl). Brain computed tomography of the pituitary gland showed no remarkable findings. A combined stimulation test for corticotropin-releasing hormone (CRH), gonadotropin-releasing hormone, and thyrotropin-releasing hormone showed a poor response to CRH stimulation. The other pituitary hormones responded well to their superordinate hormones, thus, a diagnosis of IAD was made. After hydrocortisone replacement therapy, her symptoms disappeared completely, and her ECG showed improved QT interval (QTc 0.46 sec), and ICD operation was not required.

Conclusion: We believe that the adrenal insufficiency contributed to the long-QT syndrome causing TdP, because the ECG changes improved after the initiation of steroid replacement therapy. Congenital long-QT syndrome was excluded by gene mutation screening (KCNQ1, KCNQ2, and SCN5A), and by the absence of QT prolongation in her family. Although precise mechanisms of QT prolongation by glucocorticoid insufficiency are not known, it might have been associated with glucocorticoid, which is important for the maintenance of membrane calcium transport function in the cardiac sarcoplasmic reticulum, and which extends the duration of action potential by up-regulating the expression levels of various ion channels. Based on our findings, we believe that the possibility of adrenal insufficiency should be considered in patients with QT prolongation and TdP, particularly when they have unexplained hypotension, hyponatremia, and hypoglycemia.