By indicating that ones hunger has been satisfied, the hormone leptin helps control appetite (satiety). Leptin levels in the blood are measured during this test to look for any deficiencies that might be causing obesity. The placenta in pregnant women produces leptin, but only to a smaller extent than other tissues like fat cells (adipocytes). It travels through the blood receptors in the brains hypothalamus. It signals the body that enough food has been ingested that there is no longer a need for more. In a typical feedback reaction, low leptin levels cause hunger and an increase in food intake. Hunger decreases and food intake decreases as leptin levels rise due to an increase in fat cells.