In the present patient, as there were no notable electrolyte abnormalities that would have caused LQTS (although serum magnesium was slightly low, QT prolongation persisted for two weeks after magnesium correction) and QTc shortened markedly after hormone replacement, it was hypothesized that QT prolongation was driven by a deficiency of either adrenal cortical hormone or thyroid hormone or both. Here, TG is linked to familial long QT syndrome.