Ghrelin is a hormone well known for regulating energy balance. It is a fast-acting hormone that plays a role in hunger and meal initiation. There are, however, numerous other functions of this important hormone.
Some of the functions of ghrelin include:
- Ghrelin is secreted in early fetal development and promotes lung growth.
- Ghrelin is important for a process called neurotrophy, which refers to the brain’s ability to adapt to new environments and learn new processes. Studies suggest that ghrelin enters the hippocampus of the brain from the blood and alters the connections between nerves and cells to enhance learning and memory. Learning is most effective throughout the day and when the stomach is empty, which is when ghrelin levels are higher.
- Ghrelin has been shown to play a role in preventing depression and anxiety. Mice deficient in ghrelin have also been shown to exhibit social avoidance as an effect.
- Ghrelin also plays a role in sleep, with more hours of sleep achieved the lower the ghrelin level is.
- Ghrelin stimulates the release of growth hormone from the pituitary gland.
- Ghrelin is one of the main hormones to stimulate hunger. Ghrelin levels increase before meals and decrease after meals, a mechanism that has its roots in the hypothalamus. If the lateral hypothalamus is removed (as seen in animal studies), feeding becomes less frequent leading to severe weight loss and death. If the ventromedial hypothalamus is removed, feeding increases leading to weight gain and severe obesity.
- Ghrelin and its receptors are also found in the heart and in the aorta.
- Ghrelin has also been shown to inhibit insulin secretion in some studies.