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Endocrine-related Organs and Hormones

January 24, 2022

Several organs play a major role in helping the endocrine system to work well. Although these organs are not glands themselves, they do produce, store, and send out hormones that help the body to function properly and maintain a healthy balance. 

Skin Liver and Kidneys 

The skin, liver and kidneys work together to synthesize 1,25-diydroxy vitamin D (calcitriol), the active form of vitamin D, which helps maintain normal levels of calcium and phosphorus in the blood. In the skin, a molecule made from cholesterol is converted to vitamin D by exposure to ultraviolet rays from the sun. Vitamin D undergoes further chemical changes, first in the liver and then in the kidneys, to become calcitriol. Calcitriol acts on the intestine, kidneys, and bones to maintain normal levels of blood calcium and phosphorus.

Vitamin D is a hormone the kidneys produce that controls blood calcium concentration and impacts the immune system. It is also known as calcitriol, ergocalciferol, calcidiol and cholecalciferol. Of those, calcidiol is the form doctors most commonly focus on when measuring vitamin D levels in the blood. often-misunderstood "vitamin" is not a vitamin — it is a prohormone. Prohormones are substances that the body converts to a hormone.

In fact, unlike other vitamins, only about 10 percent of the vitamin D the body needs come from food (such as dairy products and oily fish), and the rest the body makes for itself. The body makes vitamin D in a chemical reaction that occurs when sunlight hits the skin. This reaction produces cholecalciferol, and the liver converts it to calcidiol. The kidneys then convert the substance to calcitriol, which is the active form of the hormone in the body. 

Vitamin D has its effects by binding to a protein (called the vitamin D receptor). This receptor is present in nearly every cell and affects many different body processes. Researchers have found that vitamin D helps regulate adrenaline, noradrenaline (also called norepinephrine), and dopamine production in the brain; as well as helping to protect from serotonin depletion. For this reason, low vitamin D levels increase an individual's risk of depression significantly. A better understanding of vitamin D function is necessary to fully comprehend how it is linked to so many health concerns. 

What Does Vitamin D Do? 

Vitamin D helps the body absorb calcium so that blood calcium levels are at the ideal point. This helps enable the mineralization of bone that is required for strong, healthy bones. Yet this is just one function of the hormone. 

Problems Associated with Vitamin D 

Too little vitamin D means the bones will not be able to grow strong, leading to problems like rickets for children or osteoporosis for adults. Due to the weakening of bones, individuals with low vitamin D levels are more prone to falling. Low vitamin D levels can also cause a poorly functioning immune system, cardiovascular disease, depression, development of diabetes, and multiple sclerosis. It has also been linked to certain types of cancer. Even though people rarely struggle with dangerously high levels of vitamin D. If your body has too much of the vitamin it can also cause calcium levels in the blood to increase, causing hypercalcinemia. This condition can trigger confusion, depression, headaches, constipation, nausea, and feelings of thirst. Vitamin D is a hormone, and it is best to discuss your levels with a healthcare provider, consider asking: 

  • What are my vitamin D levels? What should they be? 
  • How can I get more vitamin D? 
  • What type of supplement is the best? 
  • How much vitamin D should I be taking? 

Stomach and Small Intestines 

The digestive tract is the largest endocrine-related organ system in the body. It makes and secretes several different types of hormones that play a role in the body's metabolism. 

Cholecystokinin, otherwise known as CCK or CCK-PZ, is a hormone that was once called pancreozymin because of its actions on the pancreas. This hormone has receptors through the central nervous system and gut, impacting several areas of the body. Its primary function is on digestion and the appetite, but new research has found other areas where this hormone impacts the body. 

Cholecystokinin is a hormone produced in the I-cells that line the duodenum. The hormone is also released by certain neurons in the brain. It seems to be involved in controlling appetite and plays a potential role in anxiety and panic disorders. 

How Does Cholecystokinin Work? 

Cholecystokinin's most recognized function is its ability to improve digestion. The hormone reduces the rate at which food empties from the stomach, also stimulating bile production in the liver. Bile shrinks the fat droplets, enabling enzymes to more readily break them down. At the same time, cholecystokinin increases the amount of fluid and enzymes released by the pancreas, so the body better digests food. 

In addition, this hormone increases the sensation of short-term fullness, so appetite during a meal is reduced. Some evidence has found that cholecystokinin released in the brain may have an impact on anxiety. However, this particular cholecystokinin function needs further study. 

Potential Problems With the Cholecystokinin Hormone 

Individuals who have cholecystokinin levels that are too high suffer no known ill effects. In fact, the lack of cholecystokinin side effects sparked research into using it as a weight-loss drug option, because the hormone has an appetite-reducing result. 

Too little cholecystokinin can have an adverse outcome on the body. Obese people have been found to have less than the average levels of cholecystokinin, which may contribute to problems with increased appetite and further difficulty with weight loss. In addition, variations with the cholecystokinin gene have been connected to obesity, but the reason for this is not yet known. 

While research is still underway to determine what impact cholecystokinin has on obesity and health, your healthcare provider can help you determine if your hormones may be impacting your health.  

Gastrin is a hormone the stomach produces that stimulates the release of gastric acid. It is located in the G cells in the lining of the stomach and upper small intestine. When you eat, gastrin stimulates the release of gastric acid, an important part of the digestive process. 

How Does Gastrin Do? 

Gastrin is directly responsible for the release of gastric acid, which breaks down the proteins in the food you eat. Gastric acid also helps the body absorb some of the vitamins in the food and kills much of the bacteria naturally present on food. This helps protect the gut from infection. 

Problems Associated with Gastrin 

Improper gastrin levels can instigate problems with digestion. Too much gastrin hormone is associated with Zollinger-Ellison syndrome, a syndrome caused by a gastrin-secreting tumor in the digestive system. This can release too much acid, which can create ulcers in the stomach and small intestine. If stomach acid levels are too high, it can also lead to diarrhea. 

High levels of gastrin cells and circulating gastrin hormone can also occur if the pH of the stomach is too high, which can happen when the lining of the stomach is damaged, preventing it from releasing acid. This problem can also take place when an individual is taking antacid medications due to heartburn or gastroesophageal reflux disease (GERD) 

Low gastrin levels are rare. When low levels do occur, the condition can increase the risk of infection in the digestive system and also limits the stomach's ability to absorb nutrients. 

Because gastrin is a hormone, discuss any concerns with a qualified endocrinologist. If you are worried that high gastrin levels are causing digestive symptoms, consider asking: 

  • Is gastrin responsible for my symptoms? 
  • What can I do to improve gastrin levels? 
  • How can I manage my digestive symptoms? 
  • What are the risks of these gastrin levels? 

Ghrelin is central to appetite and the release of growth hormone. Ghrelin is produced in the stomach and small intestine, with a little bit of the hormone released in the pancreas and brain. It has been called the "hunger hormone" because of its role in controlling appetite, but that is just one of its functions. 

How Does Ghrelin Do? 

Ghrelin serves many purposes, but the one most talked about is its ability to stimulate appetite, causing an individual to digest more food and store more fat. In fact, when given artificially to humans, the amount of food intake increases by 30%. The hormone plays a role in the hypothalamus, the part of the brain that controls appetite, and may act on regions of the brain that control reward processing. 

Ghrelin also plays a role in the pituitary gland’s function, where ghrelin receptors trigger the stimulation of the hormone. It appears to help control insulin release and plays a protective role in cardiovascular health. This well-rounded hormone has a job in many different bodily systems. 

Problems Associated with Ghrelin 

Because ghrelin affects appetite, it can impact weight loss, especially when someone diets. When someone is strictly controlling calories, ghrelin levels increase. This, then, causes the rebound of the pounds lost that happens right after a diet for many people. People who struggle with anorexia nervosa may also have high ghrelin levels, which occurs as part of the body's natural response to starvation. 

For patients with Prader-Willi syndrome, ghrelin levels in the blood are high. This is believed to be the reason why these patients struggle with severe obesity and extreme hunger. The ghrelin levels increase before obesity, so it is not caused by the higher body weight. 

On the other hand, patients who have gastric bypass surgery can have lower ghrelin levels than those who lose weight naturally. This may be why gastric bypass surgery, if the eating plan is followed strictly, has long-term effectiveness regarding weight loss. 

If you are trying to control your hunger and weight, understanding ghrelin function may help. Consider asking: 

  • How can I naturally control ghrelin? 
  • Are ghrelin blocker products an effective way to control hunger? 
  • Are my ghrelin levels responsible for my weight struggle? 
  • How can I lose weight without impacting ghrelin levels negatively? 

Glucagon-Like Peptide 1 (GLP-1) helps regulate your appetite, especially after eating. It also helps enhance the production of insulin. GLP-1 is produced in the gut. The cells in the small intestine are the main source of GLP-1. The pancreas and nervous system also produce GLP-1, but in smaller amounts. GLP-1 helps you feel full during and between meals by working with the brain and by slowly emptying the stomach. 

How Does Your Body Use GLP-1? 

Eating food helps stimulate your body to release GLP-1. The hormone can be found as soon as 10 minutes after eating. GLP-1 stays in your body hours after eating and circulates in the blood. 

What Problems Can Occur with GLP-1? 

Cases of in which patients have too much GLP-1 are extremely rare. However, medications have been created that act similar to GLP-1 in blood circulation to help control glucose in patients with type 2 diabetes. GLP-1 levels may also increase after bariatric surgery. If the body does not produce enough GLP-1, it may increase the odds of becoming obese. The main role of GLP-1 is to regulate your appetite after a meal. If your body isn’t releasing enough of this hormone, you may find yourself overeating or snacking between meals. However more research is needed to confirm this. People who are dieting or losing weight naturally may also experience low GLP-1 levels. 

If you are dieting and trying to control your weight, understanding the role of GLP-1 may help. Consider asking your healthcare provider: 

  • If I am dieting, how can I prevent myself from overeating or snacking between meals? 
  • How can GLP-1 help if I have type 2 diabetes? 
  • If my GLP-1 levels are low, is it responsible for my weight struggles? 

←More about Medications to Treat Diabetes 

Leptin is one of the hormones directly connected to body fat and obesity. Released from the fat cells located in adipose tissues, sends signals to the hypothalamus in the brain. Leptin hormone helps regulate and alter long-term food intake and energy expenditure, not just from one meal to the next. The primary design of leptin is to help the body maintain its weight. Because it comes from fat cells, leptin amounts are directly connected to an individual’s amount of body fat. If the individual adds body fat, leptin levels will increase. If an individual lowers body fat percentages, the leptin will decrease as well. 

What Does Leptin Do? 

Leptin is sometimes called the satiety hormone. It helps inhibit hunger and regulate energy balance, so the body does not trigger hunger responses when it does not need energy. However, when levels of the hormone fall, which happens when an individual loses weight, the lower levels can trigger huge increases in appetite and food cravings. This, in turn, can make weight loss more difficult. 

Potential Problems with Leptin 

When the body is functioning properly, excess fat cells will produce leptin, which will trigger the hypothalamus to lower the appetite, allowing the body to dip into the fat stores to feed itself. Unfortunately, when someone is obese, that individual will have too much leptin in the blood. This can cause a lack of sensitivity to the hormone, a condition known as leptin resistance. Because the individual keeps eating, the fat cells produce more leptin to signal the feeling of satiety, leading to increased leptin levels. 

Low levels of leptin are rare but can occasionally occur. For a few patients, a condition known as congenital leptin deficiency keeps the body from producing leptin. Without leptin, the body thinks it has no body fat, and this signals intense, uncontrolled hunger and food intake. This often manifests in severe childhood obesity and delayed puberty. The treatment for leptin deficiency is leptin injections. If you suspect you or your child has problems with leptin levels, consider asking: 

  • What are my leptin levels, and how do they rate? 
  • How can I handle the cravings that come when my leptin levels decrease during weight loss? 
  • Does my child need treatment for leptin deficiency? 

After eating, the hormone peptide YY (PYY) will be produced by the small intestine and released into your bloodstream. PYY communicates to your brain that you are full and decreases your appetite. The amount of PPY released depends on the type and quantity of food eaten. 

How Does Your Body Use PYY?

 After it is released in the bloodstream, PYY binds to receptors, or cells that receive signals, in the brain. It also functions by slowing down the movement of food in the digestive tract. The body produces PYY when there is food in the digestive tract, especially food that contains fat and protein. Eating high calorie foods causes your body to produce more PYY than eating low calorie foods. PYY levels are the highest two hours after eating but eventually PPY decreases. Most people have low levels of PYY after not eating for a long period of time. 

What Problems Can Occur with PYY?  

Although it is uncommon, very high levels of PYY will decrease your appetite. High PYY levels are often associated with conditions that may lead to weight loss such as eating disorders, inflammatory bowel disease and certain cancers. Low PYY levels mean that you may experience an increase in appetite. Lower PYY levels may contribute to weight gain, however it is not believed to be the main cause of obesity. It is very rare to have a genetic or endocrine disorder of PYY. 

Other Organs

When blood pressure rises, the heart releases A-type natriuretic peptide and B-type natriuretic peptide. These hormones help lower blood pressure by relaxing the arterioles, which transport blood from arteries to capillaries. It also lowers blood pressure by preventing the secretion of renin and aldosterone, as well as the reabsorption of sodium ions by the kidneys. These actions reduce blood pressure by reducing the volume of blood in the circulatory system. 

In addition to being required for bodily movements and participating in the regulation of body temperature, skeletal muscle commonly uptakes over 70% of glucose after a meal. Another key example of endocrine function of skeletal muscle includes angiogenic factors. VEGF, for example, can act on skeletal muscle and help increase blood flow to skeletal muscle, allowing for proper oxygen, nutrient, and hormone delivery to this tissue. 

Adipose tissue is typically known as body fat. Adipose tissue can be found all around the body. It is located under the skin, between muscles, and even around the organs. Adipose tissue contains many other cells that produce hormones as a response to signals from the rest of the body’s organs. Many other hormones are also released from adipose tissue and are responsible for different functions such as: 

Angiotensin- which helps control blood pressure  
Aromatase- which is involved in sex hormone metabolism  
Adiponectin- which helps improve the body’s sensitivity to insulin and protect against type 2 diabetes  

Typically, too much adipose tissue leads to obesity, which increases the risk for type 2 diabetes, high blood pressure and cholesterol, heart disease, and stroke. Too little adipose tissue can be a sign of other conditions such as lipodystrophy and anorexia. 

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