What is a Hormone? Detail Explanation

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A regulatory substance produced in an organism and transported in tissue fluids such as blood to stimulate the activity of specific cells or tissues are known as Hormones.

Understanding the major hormones and what they do will help you in controlling the health.

Hormones Definition

Hormones are chemical messengers that set in motion different processes to allow our bodies working properly.

For example, they help to regulate our metabolism, immune function, sexual reproduction, and our growth.

They are made up by specialized groups of cells in the body’s glands.

The glands, such as the pituitary gland, thyroid gland, adrenals gland, the ovaries, and testes will release hormones into the body as needed to stimulate, regulate, and to control the functioning of other tissues and organs involved in a biological process.

Healthy, sustainable food production methods give us food that is nutritionally better and with fewer pesticides, antibiotics, and hormones.

Marion Nestle (Professor of Nutrition, Food Studies, and Public Health at New York University)

Most of them are usually found in very low levels in the blood. But the concentration of a hormone varies depending on the activity or time.

We cannot survive without hormones. It helps in growing up from childhood to teenage years, they drive puberty. As we get older, a few stages clearly decline. But what does that suggest? Scientists do no longer realize precisely.

For more information, the NIA is studying the effects of hormone administration in older people how it affects frailty and functioning. Many of these studies focus on hormones that naturally decrease with age, including:

  • Human growth hormone
  • Testosterone
  • Estrogen and progesterone (as a part of hormonal treatment menopausal)
  • Dehydroepiandrosterone (DHEA)

How do Hormones Functions?

A Hormone acts on a cell like a key that opens a door. After being released by a gland, a  molecule travels in the blood until it finds the most appropriate cell.

The Hormone is blocked in a cell through the receptor of the cell. At the time it happens, a cell receives a signal.

These signals can instruct the cell to multiply, produce proteins or enzymes, or perform other important tasks. Some of them can even cause a cell to release other hormones in the body.

A Hormone may may be suitable for many types of cells but not all the cells affects the same way.

For example, a hormone can stimulate one cell to perform a task, but it can also deactivate a different cell in the same time. In Addition, the way a cell reacts to a hormone can change throughout life.

Types of Hormones List and Their Functions

Hormones are produced in the endocrine glands and pass directly from the cells of the gland to the blood that passes through them. As a general rule, the greater the amount of hormone in the blood, the more the effect you can see.

Before knowing the types of hormones you need to know about the Endocrine system.

Endocrine System includes whole glands in your body that creates hormones. These chemical messengers play a very important role in the role of your body works and the way it should be.

Here is an image showing you the major places of Endocrine System is called so.

Endocrine system


Suppose, if your endocrine system is not good in health, you might face the problems at the time of puberty, pregnancy, or mentally stress. You also might gain weight easily and may weaken your bones, or lack of energy, the reason is too much sugar stays in the blood itself instead of moving into other places to reach cells where there is the requirement of energy.

The Endocrine System classified into 2 major glands according to the functions of hormones:

  1. Endocrine Glands and
  2. Exocrine Glands

The difference between Endocrine and Exocrine Glands are:

  • Endocrine glands has ducts to move in a specific direction and effect short term it may be saliva, sweat, gastric, etc.
  • whereas Exocrine glands don’t have any ducts and it pour into the blood hence, it can effect any parts of the body for a long duration like affecting the thyroid, Pituitary and adrenals glands which may become the reason for many side effects.


Hypothalamus-Pituitary, Posterior pituitary, anterior pituitary

a) Hypothalamus

This is a region of the anterior brain under the thalamus, which coordinates the autonomic and pituitary systems, controls body temperature, thirst, hunger and other homeostatic systems and participates in the dream of emotional activity.

It contains the following Hormones and functions:

i) Thyrotrophin releasing hormone (TRH) – the function of this hormone is to release the thyroid stimulating hormone (TSH) from the anterior pituitary (as shown in the image).

ii) Somatostatin hormone – this hormone’s nature is to prevent releasing growth hormone from the anterior pituitary.

iii) Gonadotrophin releasing hormone (GnRH) – as the name tells, it releases follicle stimulating hormone (FSH) and luteinising hormone (LH) from the anterior pituitary.

iv) Corticotrophin releasing hormone (CRH) – encourages adrenocorticotrophic hormone (ACTH) to release from the anterior pituitary.

v) Growth Hormone Releasing Hormone (GHRH) – Stimulates the release of growth hormone (GH) form the same anterior pituitary.

b) Anterior pituitary

In the front side of the pituitary, a small gland in the head known to be a master gland, Hormones produced by the anterior pituitary influence our growth, improve the sexual development, the skin pigmentation, functioning of the thyroid , and adrenocortical function.

These functions influences through the effects of pituitary hormones on other endocrine glands except for Growth Hormones, which acts directly on cells.

It contains the following Hormones and functions:

i) Thyroid stimulating hormone (TSH) – It releases thyroxine and tri-iodothyronine from the thyroid gland.

ii) Luteinising hormone (LH) – This hormone functions differently for both men and women.

For Females: it promotes ovulation of the egg and produce oestrogen and progesterone production

For Males: it promotes testosterone release from the testis.

iii) Follicle stimulating hormone (FSH) – In Females, it encourages in development of eggs and follicles in the ovary prior to ovulation and In Males: it encourages in producing testosterone from testis.

iv) Growth Hormone (GH) – Growth of Bones and organs of the human body is supported by this hormone.

v) Prolactin (PRL) – It generates milk production in the breasts and plays an important role in sexual actions.

vi) Adrenocortico-trophic hormone (ACTH) – It helps the adrenal glands to produce mainly cortisol.

c) Posterior pituitary

The back part of the pituitary, a small gland in the head called the master gland. The posterior pituitary secretes oxytocin, a hormone that increases uterine contractions and antidiuretic hormone (ADH), which increases the re-absorption of water from the renal tubules of kidneys.

It contains the following Hormones and functions:

i) Vasopressin (anti-diuretic hormone, ADH) –  It fluctuates the blood pressure by causing the kidney to retain fluid and by building blood vessels.

ii) Oxytocin – It causes the serious issue of ejection of milk from the milk ducts and become a problem for the growth of uterus.

d) Thyroid gland

The thyroid gland is a gland located at the base of your neck looks like a butterfly-shaped organ, which releases hormones that control metabolism, the way the energy used by your body.

Thyroid hormones regulate the vital functions of the body, which include: Breathing, Muscular strength, Heart rate, Body temperature and much more!

It contains the following Hormones and functions:

Thyroxine (T4) – It regulates the body metabolic rate.

Tri-iodothyronine (T3) – It also regulates the metabolic rate of the body.

e) Parathyroid gland

Parathyroid glands are the four tiny glands, the area you can find in the neck that controls the calcium levels of the body.

Each gland is about the size of a grain of rice (weighs about 30 milligrams and has a diameter of 3 to 4 millimeters). The parathyroid releases a hormone called parathyroid hormone (PTH).

It contains the following Hormones and functions:

Parathyroid hormone (PTH) – Increases the calcium levels in the blood when it becomes low.

Calcitonin – It decreases the calcium levels in the blood when it becomes high.

f) Adrenal cortex

The adrenal glands (also called adrenal glands) are endocrine glands that produce various hormones, including adrenaline and the steroids aldosterone and cortisol.

They are above the kidneys. Each gland has an outer cortex that produces steroid hormones and an internal medulla.

i) Cortisol – Participates in a wide range of physiological functions, including regulation of blood pressure, the function of the immune system and regulation of blood glucose.

ii) Aldosterone – It acts to maintain blood pressure causing the retention of water and salt in the kidney.

iii) Androgens – Steroid hormones that promote the development of male features. Physiological function is uncertain.

g) Adrenal medulla

The adrenal medulla, the inner part of the adrenal gland, controls the hormones that trigger the action or reaction.

The major hormones secreted by the adrenal medulla include epinephrine (adrenaline) and norepinephrine (norepinephrine), which have similar functions.

i) Pancreas – It lowers the blood glucose level in the Muscles and tissues.

ii) Glucagon – It increases the blood glucose level in the liver.

iii) Somatostatin – It acts to inhibit the release of glucagon and insulin in the pancreas.

h) Ovary

It is a female reproductive organ in which eggs are produced, presented in humans and other vertebrates.

i) Oestrogens – It promotes the development of primary and secondary sexual characteristics of women. Important role in the preparation of the uterus for embryo implantation.

ii) Progesterone – It affects the females sexual characteristics and important to maintain the pregnancy, the affected area is breast and uterus.

i) Testis

An organ that produces sperm (male reproductive cells).

i) Testosterone – Promotes the development of male sexual characteristics, including the development of sperm.

j) Stomach

The internal organ in which most of the digestion of food is performed is an enlarged pear shaped digestive tract that connects the esophagus to the small intestine.

i) Gastrin – Promotes the secretion of acid in the stomach.

ii) Serotonin (5-HT) – It causes the contraction of the stomach muscles.

k) Duodenum and jejunum

The small intestine or small intestine is the part of the gastrointestinal tract located between the stomach and the large intestine, and is the place where the final absorption of food occurs.

The small intestine consists of three distinct regions: the duodenum, the jejunum and the ileum.

i) Secretin – It inhibits the secretions of the stomach and increases the production of bile(Bile is a dark green to yellowish brown liquid, produced by the liver in most vertebrates, which facilitates the digestion of lipids in the small intestine)

ii) Cholecystokinin (CCK) – Produces the release of bile by the gallbladder and causes the pancreas to release digestive enzymes.

l) Kidney

Each of the two organs of the abdominal cavity of mammals, birds and reptiles excretes urine and digestive waste.

i) Erythropoietin – It stimulates the development of red blood cells in the bone marrow.

m) Heart

It is a hollow muscular organ that pumps blood into the circulatory system by rhythmic contraction and dilation.

In vertebrates, there can be up to four chambers (as in humans), with two atria and two ventricles.

i) Atrial natiuretic factor (ANF) – It lowers the blood pressure and increasing the loss of salt and water in the kidneys.

n) Skin

The thin layer of tissue that forms the natural outer layer of a person’s or animal’s body is  known as Skin.

i) Vitamin D – It functions the absorption of calcium in the small intestine, calcium retention and the release of calcium from the bone reserves.

What can Hormones do?

Here are some factors that hormones do for the body. Remember though, that these are the simplest messengers.

This initiates the development of the cells into a movement, they enter the cells when it is recommended to be a better strength (the gland) and it is the cellular that does the work practically.

A) Making people to grow or prevents their growth.
B) Make humans happy or sad.
C) Speedup or slowdown the metabolism.
d) Beginning of puberty.
e) Menopause begins
f) Regulating your physiological reaction and mating.

In general, it is best to seek medical advice before the treatment because the information from the Internet may or may not be reliable.

Read also: Childhood Obesity