A hormone (from Greek hormon "that which sets in motion) is a class of biochemicals_ produced in particular parts of organisms that regulate behavior such as aggressiveness, hunger, metabolism, muscle growth, libido, sleep, and stress. Examples of hormones include adenosine, cortisol, dopamine, epinephrine (= adrenaline), estrogen, ghrelin, growth hormone, insulin_ (?), leptin_, melatonin, norepinephrine, oxytocin, secretin_, serotonin, testosterone, thyroxine_, and vasopressin_.

Hormones effectively allow organs to communicate with each other.

Hormones are studied as part of endocrinology_, which studies the `endocrine system`_. The endocrine system consists of several glands_, in different parts of the body, that secrete hormones directly into the blood.

The operation of hormones can be affected by administering drugs.

Catecholamines are hormones made by your adrenal glands. The primary catecholamines are dopamine, norepinephrine, and epinephrine.


1   History

"Hormone" was used by Hippocrates_ to denote a vital principle; modern scientific meaning coined by English physiologist `Ernest Henry Starling`_ (1866-1927).

The concept of hormones dates back to 1905. [1]

Bayliss and Starling investigated pancreatic secretion, which at that time was believed to be entirely under nervous control.[5] They showed that whenever food or acid was put into the duodenum some blood -borne stimulus was released, causing the pancreas to secrete. They called this substance secretin and Starling proposed that the body produces many secretin-like molecules, and in 1905 proposed that these substances should be called hormones. By doing this, he began a whole new biological subject, which became known as endocrinology.

Radioimmunoassay_ (RIA) made it possible to measure hormone levels in the 1950s. [1] The technology was created by `Rosalyn Yalow`_, for which she won a `Nobel prize`_. [1]

2   Function

Organs use hormones to communicate with other distant organs.

Hormones affect distant cells by binding to specific receptor proteins in the target cell resulting in a change of cell function.

3   Operation

Hormones travel through the blood to their intended target. [1]

A neurotransmitter is a chemical substance that allows nerve impulses to be transmitted from one nerve cell to another. Examples of neurotransmitters include endorphins_, dopamine, and serotonin.

An androgen is ... The androgens are testosterone and estrogen.

4   Kinds

Some hormones are steroids. These are called steroid hormones.

4.1   Aldosterone

The body does store water when needed, a whopping 1-2 liters of it. Because it is so heavy we don’t do this unless we discover we need to, i.e. we wait until an initial episode of dehydration. After an episode of dehydration, there is an change in water balance hormones (particularly aldosterone) to increase water retention. The next time you drink, the kidney retains water and promptly boosts blood volume by a phenomenal 20% on average, up to 40% in some individuals, even despite the blood dilution that this causes. Over the next two weeks the bone marrow increases red blood cell production so that hematocrit and O2 capacity per ml of plasma returns more or less to normal. The end result is that you carry around an extra 1-2 liters of blood for a while, largely to serve as a store of additional water.

4.2   Cortisol

Cortisol is a steroid hormone that is produced in the human body by the adrenal gland. It is released in response to stress and a state of fasting.

The primary functions of cortisol are to:

  • Increase blood sugar
  • Suppress the immune system, preventing the release of substances in the body that cause inflammation
  • Aid in fat, protein, and carbohydrate metabolism

Low-potency hydrocortisone is used to treat skin problems, such as eczema.

Cortisol is released in response to stress, sparing available glucose for the brain, generating new energy from stored reserves, and diverting energy from low-priority activates (such as the immune-system).

Cortisol counteracts insulin.

Long-term exposure to cortisol damages cells in the hippocampus; this damage results in impaired learning. Furthermore, it has been shown that cortisol inhibits memory retrieval of already stored information.

Cortisol levels fluctuate throughout the day. They are lowest during sleep and elevate during the day. Prolonged exposure to cortisol in response to stress weakens production capabilities, resulting in below lower average levels of cortisol after some time.

4.3   Dopamine

Dopamine is a neurotransmitter.

Some drugs, like Methamphetamine and cocaine and amphetamine and methylphenidate can certainly cause long term irrreversible changes in dopamine receptors and reuptake pumps, but this usually only happens in cases where these drugs are being abused for an extended period of time in large amounts.

A very grossly general rule about all this that the more chemically similar to meth and coke the substance is, the more likely prolonged abuse of large amounts with damage your dopaminergic mechanisms permanently. Amphetamine and methylphenidate are pharmacologically similar to meth and coke, respectively.

4.4   Endorphin

An endorphin is a chemical neurotransmitter that is naturally produced in the blood. Endorphins create a feeling of pleasure.

"Endorphin" is derived from "endogenous morphine" or "morphine produced naturally in the body".

4.5   Epinephrine

Epinephrine (from Greek epi- "upon" + Greek nephros "kidney" + -ine, so called because the adrenal glands are on the kidneys) (= adrenaline) is a hormone produced by the adrenal glands. (The name "adrenaline" comes from a company that tried to patent a synthetic epinephrine compound, and the name stuck.)

When adrenaline is released, it seems to prime the brain to remember things in unusual clarity.

The reason we can't do this all the time is obvious - it puts much more strain on the body and consumes far more energy. Since our bodies evolved in times of scarcity, our bodies evolved a logical mechanism for limiting the bodies ability to use its full strength and energy; only when the brain sensed certain stimuli (a tiger, a child in trouble), would it release its natural chemicals that overrode its own internal limiters, allowing for a brief state of higher muscle performance.

4.6   Estrogen

Estrogen is a hormone that is produced primarily in the ovaries in women and in the testes in men. Estrogen is also produced by other tissues in both men and women, including fat and the brain. If fat levels are lower enough, estrogen may decrease in women to cause amenorrhea (lack of a period).

For men, it plays an important role in sperm production and bone maintenance. The amount of estrogen needed by men to support these functions is very small.

Men tend to have excess estrogen in their system for two reasons:

  1. An enzyme called aromatase that is found in tissues throughout the body will turn testosterone into estrogen. Aromatase is found in body fat, meaning that men with more fat will produce more aromatase, and therefore have higher estrogen and lower testosterone.

    Aromatase can be blokced by eating or supplementing with nutrients that do this naturally.

  2. Chemical estrogens in the environment, such as BPA and phtalates. BPA is a petroleum based chemical that mimics estrogen in the body.


A suspected link between abnormal breast growth in young boys and the use of lavender and tea tree oils has been given new weight, after a study found eight chemicals contained in the oils interfere with hormones.

The American study found that key chemicals in the oils boost oestrogen and inhibit testosterone.

A previous study by Dr Kenneth Korach - who was also co-investigator for this study - found that lavender and tea tree oil had properties that competed with or hindered the hormones that control male characteristics, which could affect puberty and growth.

4.7   Gamma-aminobutyric acid

Gamma-aminobutyric acid (GABA) functions naturally in the brain as an inhibitory neurotransmitter. Thus GABA is associated with the brain's own natural calming response.

Drugs that treat anxiety, such as benzodiazepine_, stimulate GABA receptors to induce a calming effect.

4.8   Ghrelin

Ghrelin is a hormone which makes people crave carbohydrates and sugar.

4.9   Growth Hormone

The lack of this causes growth hormone deficiency.

4.10   Levonorgestrel

Levonorgestrel is a hormone that can be used for emergency contraception.

4.11   Norepinephrine

Norepinephrine (from "normal", in reference to molecular structure, + epinephrine) is an organic chemical that functions in the body as a hormone and neurotransmitter.

The general function of norepinephrine is to ready the brain and body for action. Norepinephrine release is lowest during sleep, rises during wakefulness, and reaches much higher levels during situations of stress or danger, in the so-called fight-or-flight response.

Norepinephrine increases arousal, alertness, memory formation, attention, heart rate and blood pressure, increases the flow of blood to skeletal muscle.

4.12   Oxytocin

Oxytocin is a hormone that facilitates these moments of shared intimacy and is part of the mammalian "calm-and-connect" system (as opposed to the more stressful "fight-or-flight" system that closes us off to others). [1]

Oxytocin is released in huge quantities during sex, and in lesser amounts during other moments of intimate connection, works by making people feel more trusting and open to connection. [1] Researchers have found, for instance, that when a parent acts affectionately with his or her infant—through micro-moments of love like making eye contact, smiling, hugging, and playing—oxytocin levels in both the parent and the child rise in sync. [1]

Also oxytocin, the "cuddle hormone" that is usually associated with love or caretaking behaviour, is associated with increased aggression towards non-members of the own group. This is why you should never get between a parent animal and its babies (or humans and their children, for that matter).

4.13   Serotonin

Serotonin (coined 1948 from "serum" + "tonic" + "-in") is a hormone that is thought to regulate mood, appetite, sleep, memory, and libido.

Too much serotonin can also inhibit libido and make it harder to orgasm. It's also possible that as serotonin increases, dopamine is reduced. Dopamine is a neurotransmitter that actually facilitates arousal (among other things), so if you're secreting less of it, you'll have a harder time getting and staying turned on.

The relationship between low serotonin levels and anxiety or depression (once, and to some extent still, the theoretical reason SSRIs, which boost serotonin, should work) now seems less straightforward than previously thought. George Ashcroft, who, as a research psychiatrist in Scotland in the 1950s, was one of the scientists responsible for promulgating the chemical-imbalance theory of mental illness, abandoned the theory when further research failed to support it. “We have hunted for big, simple neurochemical explanations for psychiatric disorders,” Kenneth Kendler, a co-editor of Psychological Medicine and a psychiatry professor at Virginia Commonwealth University, conceded in 2005, “and have not found them.” [3]


Deficiency in serotonin - a chemical messenger in the brain - plays a central role in depression In the journal ACS Chemical Neuroscience, scientists report that mice lacking the ability to make serotonin in their brains (and thus should have been "depressed" by conventional wisdom) did not show depression-like symptoms.

In the late 1980s, the now well-known antidepressant Prozac was introduced. The drug works mainly by increasing the amounts of one substance in the brain - serotonin. So scientists came to believe that boosting levels of the signaling molecule was the key to solving depression. Based on this idea, many other drugs to treat the condition entered the picture. But now researchers know that 60 to 70 percent of these patients continue to feel depressed, even while taking the

drugs. Kuhn's team set out to study what role, if any, serotonin played in the condition.

To do this, they developed "knockout" mice that lacked the ability to produce serotonin in their brains. The scientists ran a battery of behavioral tests.

Interestingly, the mice were compulsive and extremely aggressive, but didn't show signs of depression-like symptoms. Another surprising finding is that when put under stress, the knockout mice behaved in the same way most of the normal mice did

5   Adrenal insufficiency

Adrenal insufficiency is a symptom of some corticosteroid_ medicines when people stop taking the medicine or when they take higher doses over a long period of time. When your body is under stress from fever, trauma, or surgery, adrenal insufficiency can get worse.

Signs and symptoms include:

6   References

[1](1, 2, 3, 4, 5, 6, 7) Emily Esfahani Smith. Jan 25 2013. There's No Such Thing as Everlasting Love (According to Science). http://www.theatlantic.com/sexes/archive/2013/01/theres-no-such-thing-as-everlasting-love-according-to-science/267199/?utm_source=SFFB
[2]Angela Chen. Aug 7, 2018. How hormones went from theoretical to overhyped in one century. https://www.theverge.com/2018/8/7/17660818/randi-epstein-aroused-hormones-endocrinology-health-science
[3]Scott Stossel. Jan 2014. Surviving Anxiety. http://www.theatlantic.com/magazine/archive/2014/01/surviving_anxiety/355741/?single_page=true
[6]Aug 29, 2014. Serotonin may not be a major factor in depression, study suggests. http://www.medicalnewstoday.com/releases/281645.php

Mary Lou Jepsen, after brain surgery, no longer naturally produced hormones. She relies on a daily drug cocktail to produce the hormones she needs to survive. However, she can also alter them to achieve certain mental states. She mentioned she can control the amount of cortisol to eliminate jet lag.

I wonder what chemicals she uses? She mentioned some are illegal, such as growth hormone.