Part 10: What Are Hormones, And What Do They Do?

Hormones are chemicals that are created within our body


Do not take any OVER THE COUNTER products that promise to help you until it is confirmed by your doctor as being useful for you. The following information is to tell you about what a hormone does. The amounts used by our body are very carefully balanced and taking more doesn't make sense. Be careful, learn about everything and if you think you might need some changes you will need a blood test and discuss it with trained professionals. Media, sales advertisements and news stories of medical breakthroughs are not to be trusted.

You need to also read about vitamins

As part of our series on the human brain it is important to look at the whole body because our body physiology seems to be under the control of brain. Any injury or emotional disturbance to the brain can lead to alteration in secretion of hormones. Therefore when we research the effect of sexual assault we expect to see during emotional changes hormonal imbalance happening. There is a lot of things going on.

They control most of our bodily functions, ranging from simply making us feel hungry to assist in reproduction. They can even influence our brain and how we feel about things. This simple explanation will help you understand just a little bit about how important hormone functions are to your health. If you need some help with any problems it is important to consult your doctor as this post is only a very small part of a very complex system.


Prostaglandins are created right on the place where you suffer an injury. It is just like having a doctor standing next to you just in case you get hurt. This makes them different to all other hormones because they are not secreted from a gland. Here is what it does when your body is damaged or infected:

  • It creates the reactions that cause pain, fever and inflammation and starts the healing process.
  • It also helps form a blood clot or contraction of the blood vessel wall when your body is bleeding.
  • When the blood clots are not needed (the injury begins to heal) it makes changes that allow the clots to go and the blood vessel wall to relax.
  • In women, it assists in regulating the reproductive system; can start labour and control ovulation. ("Synthetic" prostaglandins sometimes are used to induce labour in pregnancy).


Adrenaline is produced in the adrenal glands as well as some of the central nervous system's neurons. When needed, it is quickly released into the blood, sending impulses to organs to create a specific response.

It is used when you are in very serious trouble and your brain and body move into a survival mode. The brain is monitoring the situation in microseconds searching for memories that might be relevant and recording new.

At the same time, again very rapidly the Adrenaline causes some blood vessels to contract and air passages to dilate to provide the muscles with the oxygen they need to either fight danger or run away. This might cause breathing to become rapid and blood pressure increases. Aldosterone tries to make sure that it is within safe limits. Sadly sometime people with a weak or diseased heart don't survive

Adrenaline also decreases your ability to feel pain which is why you can continue running from or fighting danger even when injured. It also causes a noticeable increase in strength and as we mentioned before the brain is not missing any single microsecond monitoring all senses and everything happening within the body and everything around you in any stressful times. Once the event is over and the danger is manageable the adrenaline stops however its effect can last for up to an hour.


Aldosterone affects the regulation of blood pressure. It sends the signal to organs, like the kidney and colon, that can increase the amount of sodium the body sends into the bloodstream or the amount of potassium released in the urine. Indirectly, the hormone also helps maintain the blood's pH and electrolyte levels.

It is closely linked to two other hormones: renin and angiotensin, which create the renin-angiotensin-aldosterone system. This system is activated when the body experiences a decrease in blood flow to the kidneys, such as after a drop in blood pressure, or a significant drop in blood volume after a haemorrhage or serious injury. Renin is responsible for the production of angiotensin, which then causes the release of aldosterone.


Calcitonin is a hormone produced in the thyroid gland. It works to control calcium and potassium levels. It does this by inhibiting the activity of the osteoclasts, the cells that break down bone. By preventing the breakdown of bone, calcitonin lessens the amount of calcium in the blood. It also may decrease the amount of calcium the kidneys can re-absorb, lowering levels further.

Secretion of this hormone is controlled directly by the blood's calcium levels. When the levels start to increase, the body responds with increased calcitonin levels. When calcium levels drop, so do calcitonin levels.


Cortisol is one of the steroid hormones and is made in the adrenal glands. Most cells within the body have cortisol receptors. Secretion of the hormone is controlled by the hypothalamus, the pituitary gland and the adrenal gland. Cortisol can help control blood sugar levels, regulate metabolism, help reduce inflammation and assist with memory formulation. It has a controlling effect on salt and water balance and helps control blood pressure. In women, cortisol also supports the developing foetus during pregnancy.


Erythropoietin is a hormone which is produced predominantly by the kidney. It acts on red blood cells to protect them against destruction. At the same time it stimulates stem cells of the bone marrow to increase the production of red blood cells. Not much is known about it but it is well known that specialised cells in the kidney are capable of detecting and responding to low levels of oxygen through increased production of erythropoietin. When there is sufficient oxygen in the blood circulation, the production of erythropoietin is reduced, but when oxygen levels go down, the production of erythropoietin goes up.

  • Examples of the need to release it when less oxygen available
    • High altitude
    • Emphysema
    • Cardiovascular disease
  • Example of when less is released
    • Kidney failure
    • AIDS
    • Some Cancers
    • Inflammatory diseases like rheumatoid arthritis


Glucagon is a hormone that works with other hormones and bodily functions to control glucose levels in the blood. It comes from the pancreas

  • When blood sugar levels drop, you may feel lethargic, or if they drop too low, become disoriented, dizzy or even pass out.
  • Glucagon directly impacts the liver as it works to control blood sugar levels.
  • It prevents blood glucose levels from dropping to a dangerous point.
  • It stops the liver from consuming some glucose.
  • It produces glucose in the amino acid molecules.

In each of these processes, glucagon and insulin work together. Insulin will prevent glucose levels from increasing to a point that is too high, while glucagon prevents it from dropping too low.

Ghrelin and Leptin

Ghrelin is a hormone that is produced and released mainly by the stomach when its empty, with small amounts also released by the small intestine, pancreas and brain. Ghrelin has numerous functions. It is termed the 'hunger hormone' because it stimulates appetite, increases food intake and promotes fat storage.

Leptin is made by fat and is secreted into the circulatory system, where it travels to the hypothalamus. Leptin tells the hypothalamus that we have enough fat, so we can eat less or stop eating.


Insulin is created by the pancreas. It allows the cells in the muscles, fat and liver to absorb glucose that is in the blood. The glucose serves as energy to these cells, or it can be converted into fat when needed. Insulin also affects other metabolic processes, such as the breakdown of fat or protein.


Leptin, a hormone released from the fat cells located in adipose tissues. It helps the body maintain its weight.

  • Because it comes from fat cells, Leptin amounts are directly connected to the amount of body fat.
  • It helps inhibit hunger and regulate energy balance, so the body does not trigger hunger responses when it does not need energy.
  • But when levels of the hormone fall, (say on a diet), the lower levels can trigger huge increases in appetite and food cravings. This is why losing weight is difficult


Melatonin is created by the pineal gland in the brain.

  • It send messages around the body for the need to sleep
  • As night reduces the amount of light Melatonin increases
  • It signals relaxation and lower body temperature that help with restful sleep.


In women, oxytocin is responsible for signalling contractions of the womb during labour. The hormone stimulates the uterine muscles to contract, so labour begins. It also increases the production of prostaglandins, which move labour along and increases the contractions even more. Once the baby is born, oxytocin promotes lactation by moving the milk into the breast. When the baby sucks at the mother's breast, oxytocin secretion causes the milk to release so the baby can feed.

For men, oxytocin function is less important, but it does have a role to play in moving sperm. It also appears to affect the production of testosterone in the testes.

It is oxytocin that triggers the bond between a mother and an infant, and it may also play a role in recognition, sexual arousal, trust and anxiety. Some research shows that the hormone may affect addiction and stress as well.


Progesterone is secreted by the corpus luteum, a temporary endocrine gland that the female body produces after ovulation during the second half of the menstrual cycle.

Progesterone prepares the endometrium for the potential of pregnancy after ovulation. It triggers the lining to thicken to accept a fertilized egg. It also prohibits the muscle contractions in the uterus that would cause the body to reject an egg. While the body is producing high levels of progesterone, the body will not ovulate.

If the woman does not become pregnant, the corpus luteum breaks down, lowering the progesterone levels in the body. This change sparks menstruation. If the body does conceive, progesterone continues to stimulate the body to provide the blood vessels in the endometrium that will feed the growing baby. The hormone also prepares the limit of the uterus further so it can accept the fertilized egg.

Once the placenta develops, it also begins to secrete progesterone, supporting the corpus luteum. This causes the levels to remain elevated throughout the pregnancy, so the body does not produce more eggs. It also helps prepare the breasts for milk production.


Prolactin is produced in the pituitary gland, the uterus, immune cells, brain, breasts, prostate, skin and adipose tissue.

Prolactin is a hormone named originally after its function to promote milk production. Actually it has more than 300 functions in the body. Linked with Dopamine, Oestrogen, thyrotropin, oxytocin


Testosterone is produced in the ovaries in women, the testes in men, and the adrenal glands in both genders. It is an androgen, or a hormone that stimulates the development of male characteristics. While men have it in higher amounts, both men and women have testosterone to some extent.

Testosterone is the hormone that initiates the internal and external development of a male foetus, including the reproductive organs. It plays an important role during male puberty, sparking growth spurts, hair growth and genital changes. It can also cause aggressive and sexual behaviour in men.

For men and women, testosterone signals the body to make new blood cells, so the muscles and bones stay strong during and after puberty. It enhances libido for both genders.


The thyroid gland is an important part of the endocrine system, secreting a number of hormones that affect everything from heart health to metabolism. One of these is thyroxin, also known as T4. Because of the many functions that thyroxin impacts, it is considered one of the most important thyroid hormone.

  • Thyroxin is a hormone the thyroid gland secretes into the bloodstream.
  • It travels to the liver and kidneys, where it is converted to its active form of triiodothyronine.
  • It is important to the heart and digestive function, metabolism, brain development, bone health and muscle control

Vitamin D

Vitamin D is not a vitamin it's a hormone. In fact, unlike other vitamins, only about 10%  of the vitamin D the body needs comes from food, and the rest the body makes for itself. It is made by the kidneys and controls blood calcium concentration and impacts the immune system.

The body also makes vitamin D in a chemical reaction that occurs when sunlight hits the skin. This reaction produces cholecalciferol, and the liver converts it to calcitriol. The kidneys then convert the substance to calcitriol, which is the active form of the hormone in the body.

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.

Vitamin D deficiency has been linked to a variety of health concerns, which points to a wide range of vitamin D functions, although research is still underway into why the hormone impacts other systems of the body. For instance, too little vitamin D makes an individual more prone to infections and illness, cardiovascular disease and mental illness - including mood disorders like depression. Researchers have found that vitamin D helps regulate adrenaline, noradrenaline 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.

Endocrine System

The endocrine system's glands work together with the brain to create and manage the body's major hormones . The main hormone-producing glands are:

  • Hypothalamus: The hypothalamus is responsible for body temperature, hunger, moods and the release of any hormone from other glands; and also controls thirst, sleep and sex drive.
  • Parathyroid: This gland controls the amount of calcium in the body.
  • Thymus: This gland plays a role in the function of the adaptive immune system and the maturity of the thymus, and produces T-cells.
  • Pancreas: This gland produces the insulin that helps control blood sugar levels.
  • Thyroid: The thyroid produced hormone associated with calorie burning and heart rate.
  • Adrenal: Adrenal glands produce the hormone that controls sex drive and cortisol, the stress hormone.
  • Pituitary: Considered the "master control gland," the pituitary gland controls other glands and makes the hormone that trigger growth.
  • Pineal: Also called the thalamus, this gland produces serotonin derivatives of melatonin, which affects sleep.
  • Ovaries: Only in women, the ovaries secrete oestrogen, testosterone and progesterone, the female sex hormones.
  • Testes: Only in men, the testes produce the male sex hormone, testosterone, and produce sperm.


Part 1: Study of the Human Brain

Part Two: A child is born

Part 3: What we put into our body that affects our minds

Part 4: What we put into our minds that effects our Brain

Part 5: How do other people's actions change us

Part 6: Does our Brain Sleep?

Part 7: How important is our body condition to our brain health

Part 8: Why do we sometimes forget simple things : Lost keys

Part 9: Why do we never forget bad things


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