Leptin, the product of the ob (obese) gene, is produced mainly in the adipose tissue, and is considered to play an important role in appetite control, fat metabolism and body weight regulation. The primary effect of leptin appears to be mediated by leptin receptors expressed mainly in the hypothalamus. In humans, leptin levels correlate with body mass index (BMI) and percentage body fat, and are eelevated even in obese individuals. Leptin has a dual action; it decreases the appetite and increases energy consumption. Leptin is secreted in circadian fashion with nocturnal rise in both lean and obese patients. Mutations of the ob gene resulting in leptin deficiency are the cause of obesity in the ob/ob mice suggesting that endogenous leptin can normalize body weight. In contrast, human obese subjects may have high levels of leptin, indicating a mechanism of leptin resistance. Download the catalog