Leptin, which is produced by adipocytes, is known to be an important regulator of food intake and energy storage. Disturbance of thyroid function is associated with marked changes in both body weight and energy expenditure, and it has therefore been the subject of much research to study the mutual roles of leptin and thyroid hormones in this respect. Despite intensive research in this field, results are still not very clear. The aim of this review has been to update the current state of knowledge of leptin related to thyroid pathophysiology.