Ghrelin How ghrelin is controlled? What happens if you have too much ghrelin? What happens if you have too little ghrelin? Functions of ghrelin


Basically a hormone, ghrelin is produced by specific cells that are found in the lining of the stomach as well as the pancreas. Cells known as P/D1 cells secrete ghrelin in the upper region of the stomach, which is also referred to as "fundus". On the other hand, the cells that secrete ghrelin in the pancreas are known as epsilon cells. Aside from the stomach and pancreas, ghrelin is also found in much smaller amounts in the hypothalamus, pituitary gland, placenta and kidneys. Moreover, this hormone is also produced in small amounts by a few neurons found in the arcuate nucleus.

Several hormones work to stimulate hunger and ghrelin is prominent among them. It has been found that the levels of ghrelin increases in our body before meals and their levels automatically decrease after meals. This mechanism related to the rise and ebb of ghrelin secretion is controlled in the hypothalamus. Findings of studies undertaken on animals have shown that when the lateral hypothalamus is done away with, the subject feeds less frequently resulting in acute weight loss and subsequent death of the animal. On the other hand, when the ventromedial hypothalamus is got rid of, the opposite happens. It causes frequent consumption of food resulting in substantial weight gain, which leads to severe obesity.

Leptin is another hormone that neutralizes the results of ghrelin. Adipose tissues or fat present in our body produces the hormone leptin. The hormone leptin is responsible for inducing a feeling of fullness or satiation after a meal. Hence, it is natural that elevated levels of leptin in our body reduce hunger. As ghrelin is responsible for increasing hunger, many weight loss programs try to decrease the levels of ghrelin by increasing the feeling of fullness even after taking a small meal.

It is worth noting here that ghrelin is also said to promote growth hormones, which are secreted from the body's anterior pituitary gland. The reason for this is that special ghrelin receptors are present in the anterior pituitary glands. In fact, scientists discovered the special ghrelin receptors much before they discovered the hormone ghrelin. Because of this, ghrelin receptors are often known as the growth hormone secretagogue receptor (GHS-R). Aside from the anterior pituitary gland, ghrelin receptors are also present in the adipose tissue, hypothalamus and even our heart.

It has been found that ghrelin also works to invigorate the appetite. It augments the appetite prior to a meal and then reduces it after one has taken the meal. During laboratory tests, it was found that people who were administered ghrelin injections claimed that their hunger increased substantially. Moreover, several studies have shown that ghrelin works to holds back the body from utilizing fat present in the adipose tissue. Basically, it has been found that the hormone ghrelin is somewhat responsible for allowing our body to make out when it is actually hungry. In addition, this hormone also helps our body know precisely about the balance of energy in the brain and our body.

Inside the stomach or the gastrointestinal system, this hormone promotes the vacating of the the gastric system. In addition, ghrelin also seems to have a positive effect on the functioning of our cardiovascular system in various ways. It works by enhancing the productivity of the cardiac system. However, scientists are still uncertain about the reason behind the positive effects. They are still unsure as to whether these positive effects are an outcome of ghrelin itself or owing to the impact of ghrelin's action that promotes secretion of the growth hormones.

As discussed above, ghrelin also impacts the functioning of the brain. Apparently, this hormone plays a major role in neurotrophy, particularly because it is related to the hippocampus. Apart from this, ghrelin plays a vital role in facilitating the brain in making cognitive adjustments as well as various other modifications as needs to adapt to new environments. This way, ghrelin also plays an important role in our learning process and progression.

How ghrelin is controlled?

It has been established that basically our food intake regulated the levels of ghrelin in our body. Studies have found that ghrelin levels in the blood stream increase when we are fasting and just before we take a meal. Our normal routine of food intake has an effect on the timing of rise in ghrelin levels. Therefore, it is believed that ghrelin has a significant role in the "hunger pangs" we experience before our mealtime, which leads us to take our meal. As in the case of heightened hunger, ghrelin levels also rise in the blood stream when we are fasting. Interestingly, the levels of ghrelin are lower in people having higher body weight than those with lesser body weights. This is an indication that this hormone may possibly be associated with regulating the body's weight in the long-term.

Soon after we eat something, the level of ghrelin decreases in the blood stream. It has been found that different nutrients have the ability to hold back secretion of ghrelin in varying degrees. Studies have shown that carbohydrates and proteins slow down ghrelin production as well as secretion more compared to ingested fats.

In addition to carbohydrates, proteins and fats, another substance called somatostatin also possesses the aptitude to curb release of ghrelin. Moreover, several other hormones produced in the gastrointestinal system can also restrict the secretion of ghrelin.

What happens if you have too much ghrelin?

Since the levels of ghrelin in the blood stream increases while fasting or dieting, it is clear that efforts to lose weight through dieting is quite difficult. Generally, people would assume that ghrelin levels are higher in obese people. But the fact is that people with more body weight usually have lower levels of ghrelin in the blood stream compared to lean individuals. This phenomenon hints that this hormone is not responsible for obesity. Nevertheless, it is thought that people who are obese are more responsive to ghrelin. Hence, it is accepted by most that further studies are necessary to understand the role of this hormone thoroughly.

Some people suffering from extreme hunger, severe obesity and facing difficulties in learning often suffer from a genetic disease called Prader-Willi syndrome. Different from the other common types of obesity, patients suffering from Prader-Willi syndrome have very high levels of ghrelin in the blood stream even before they start becoming obese. This puts forth the theory that ghrelin may add to such people's augmented appetite as well as increased body weight.

This apart, people suffering from anorexia nervosa, which is actually eating disorder, and cachexia also have high levels of ghrelin in their blood stream. Perhaps, by this way the body compensates for such people's weight loss by means of encouraging intake of food and storing ingested fats.

What happens if you have too little ghrelin?

There are a few ways by which one can decrease ghrelin in the blood stream. However, gastric bypass surgery is considered to be the most effective means to reduce secretion of this hormone than any other means, such as exercise and dieting. This surgery involves reducing the stomach�s size and is known to be the best treatment of acute, life-threatening obesity. It has been found that obese people who lose their body weight following gastric bypass surgery have lower levels of ghrelin compared to people who undertake dieting and exercise to lose weight. To some extent, this explains the effectiveness of gastro bypass surgery in treating obesity.

Functions of ghrelin

From the above discussion we can come to the conclusion that ghrelin has a prominent part in inciting hunger and, thereby, contributing to weight gain. Discovered by researchers in 1996, ghrelin is also known as growth hormone secretagogue (GHS) receptor. This hormone gets its name ghrelin owing to its role in releasing the growth hormone called peptide. While ghrelin contributes to weight gain and obesity, this hormone is also vital for a bodily process known as neurotrophy. Neurotrophy is related to the ability of the brain to learn new processes and become accustomed to new environments.

Findings of various studies hint that our blood stream carries ghrelin to the brain and there this hormone modifies the relation between the cells and the nerves to improve our learning as well as memory. It is interesting to note that the learning process is most effectual all through the day and also on an empty stomach. During both these times, the levels of ghrelin are relatively higher in the blood stream.

Ghrelin has several functions and it fulfils a number of purposes. Of these, the most common and well known function of this hormone is its aptitude to invigorate appetite, which goads a person to eat and digest additional food. This leads to storage of more fat in the body. Precisely speaking, when ghrelin is administered artificially via injections to humans, their food intake is enhanced by roughly 30 percent. Ghrelin also has an important part in the region of the brain called hypothalamus. In fact, the hypothalamus regulates our appetite. In addition, the hypothalamus may also affect other areas of the brain that are in-charge of reward processing.

Ghrelin has other functions too. One of them is this hormone's role in the functioning of the pituitary gland. It is in the pituitary gland that ghrelin receptors set off the activation of ghrelin. Apparently, ghrelin also regulates secretion of insulin and has a protective role vis-�-vis the health of our cardiovascular. To sum it up, ghrelin is a versatile hormone which plays important roles in several bodily functions.

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