Out of Left Field: An Unsuspected Cause of Atrial Fibrillation

Fibrosis of atrial tissue is a cause of atrial fibrillation (AF). But what mediates development of atrial fibrosis? An international team reports that the hormone calcitonin is produced by atrial myocytes and diminishes production of collagen by atrial fibroblasts. In mice, increasing atrial calcitonin production prevents fibrosis and AF, whereas inhibiting calcitonin production (or knocking out the calcitonin receptor) enhances fibrosis and AF. In a mouse model for AF, increasing the production of calcitonin greatly reduced the likelihood that AF would develop.

Human atrial myocytes also make calcitonin, and human atrial fibroblasts also have receptors for calcitonin. Moreover, human patients with persistent AF have impaired atrial producti…