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What Are Hormones?

Hormones are chemical substances that act like messenger molecules that stream through the bloodstream. Hormones carry chemical messages from the glands where they are produced to cells in different parts of the human body. These chemical messages help to turn on or turn off cellular processes that control stress, appetite, growth, sleep cycles, blood sugar, sex drive, and sexual function.

The importance of hormones in the proper functioning of the human body is immense. They control the functions of organs and influence their growth, reproduction and sexual characteristics.

Moreover, hormones also affect the way a human body stores and uses energy and regulates the volume of fluids as well as the level of sugar and salt in the blood. Thus, a small amount of hormone can trigger a significant response in the human body.

What are Hormones?

Hormones are various chemicals released within the human body that regulate and control the activities of multiple organs. The introduction of hormones to the blood takes place via endocrine glands.

Our body contains two different kinds of glands.

  1. Endocrine Glands: These glands, such as the pituitary and adrenal glands, do not have ducts and deliver their secretions through the blood straight to the site of action.

  2. Exocrine Glands: These glands have ducts by which their secretions are transported. Example: sweat and liver,

Endocrine glands secrete “Hormones”.

What Is the Function of Hormones?

Hormones act as a messenger which is released into the blood. Blood transmits them to various organs and tissues of the human body. After reaching a target site, hormones bind to the receptors. Once this process is complete, hormones then transmit the message which causes an organ or tissue to perform a specific action.

The following are some important functions of hormones:

  • Regulating mood and cognitive functions

  • Growth and development

  • Food metabolism

  • Maintaining body temperature

  • Controlling thirst and hunger

  • Initiating and maintaining sexual development and reproduction

Hormone Regulation

Hormones may be regulated by glands and organs, by a negative feedback mechanism, or by other hormones. Hormones that regulate the release of other hormones are defined as tropic hormones, which are secreted by the anterior pituitary in the brain.

Hormones During Pregnancy

Many hormone levels are affected in the body during pregnancy. Several hormones play major roles during pregnancy such as Estrogen, Progesterone, human chorionic gonadotropin hormone (hCG), and Human placental lactogen (hPL).

Chemical Nature of Hormones

Hormones may be chemically classified as either proteins or steroids. All of the hormones in the human body, except the sex hormones and those from the adrenal cortex, are proteins or protein derivatives.

What are The Properties of Hormones?

The significant properties of hormones are –

  1. They have a low molecular weight; thus, they can easily pass through capillaries.

  2. Hormones always act in low concentration.

  3. They are soluble in water so that they can be transported via blood.

  4. The importance of hormones is that they are non-antigenic. They are organic catalysts. Hormones act as coenzymes of other enzymes in the human body.

  5. Hormones, in their first action, cause a limited number of reactions and do not influence any metabolic activities of a cell directly.

  6. A significant characteristic of hormones is that, after their function is over, they are readily destroyed, excreted or inactivated.

  7. Hormonal activities are not hereditary.

Characteristics of Hormones

Hormones possess the following characteristics:

  • Endocrine cells release hormones into the body.

  • Circulating in bodily fluids, hormones are chemical messengers.

  • They act on one portion of the body after being secreted in another.

  • Unlike enzymes, hormones do not catalyse any reactions.

  • They are not stored beforehand and are only secreted in minute amounts when necessary.

  • The nervous system uses the feedback effect to control hormone secretion.

  • The majority of the time, hormones have long-lasting impacts such as altered behaviour, growth, etc.

Classification of Hormones

The hormones produced in the human body are classified based on their chemical structure and nature as follows:

  1. Peptide/Protein Hormones:

These hormones are made of polypeptide chains—linked chains of amino acids. The secretory vesicles serve as both a place for peptide hormone synthesis and storage. They are located in the membrane of the cell and are expelled from the parent cell through exocytosis. After being stored in vesicles, the substance is released when a stimulus causes a reaction, such as when high blood glucose levels cause the release of insulin. These hormones are water soluble but not fat soluble. The cell membrane comprises a phospholipid bilayer that prevents any fat-insoluble compounds from diffusing into the cell, preventing peptide hormones from passing through the membrane. Since the peptide hormones are unable to pass through the cell's plasma membrane, the receptors are present on the target's cell surface.

ADH (antidiuretic hormone), which is produced in the brain and released into the circulation by the posterior pituitary gland, is one example along with oxytocin and vasopressin.

  1. Steroid Hormones:

These hormones are lipid-derived hormones that are obtained from cholesterol. On-demand, they are synthesised from precursors and released from the parent cell by a simple diffusion process. These hormones typically have the goal response of inducing the synthesis of new proteins because they bind to proteins while being transported through the blood. Steroid hormones, in contrast to peptide hormones, are fat-soluble and may pass through the cell membranes. Steroid hormones comprise sex hormones including progesterone, estrogen, and testosterone.

Functions of Hormones

The following are a few important functions that hormones perform:

  • Metabolism of food.

  • Development and growth.

  • Controlling hunger and thirst.

  • Preserving one's body's temperature.

  • Maintain Homeostasis

  • Regulating sleep and wake cycle

  • Regulating mental and emotional functions.

  • Establishing and sustaining sexual development and reproduction

Endocrine Glands and the Hormones Secreted by Them

Endocrine Gland


Target Tissue/Organ


Anterior Pituitary Gland

Growth Hormone

Most Tissues

Influences development and growth, activate the synthesis of proteins and modifies the distribution of fat

Thyroid-Stimulating Hormone (TSH)

Thyroid Gland

Promotes the synthesis and release of thyroid hormones

Adrenocorticotropic Hormone (ACTH)

Adrenal Cortex

Promote secretion of glucocorticoid hormones.

Melanocyte-Stimulating Hormone (MSH)

Melanocytes In Skin

Promotes melanin production in the melanocytes present in the skin

Luteinizing Hormone (LH)

Ovaries In Females

Stimulates ovulation and production of progesterone in ovaries

Follicle-Stimulating Hormone (FSH)

Follicles Present In The Ovaries Of A Female

Helps in follicle maturation and oestrogen production in ovaries


Mammary Glands And Ovaries In Female

Promotes milk production in breasts

Posterior Pituitary Gland

Antidiuretic Hormone (ADH)


Influences kidney water retention and regulates blood pressure


Uterus, Mammary Gland

Stimulates uterine and breast milk duct contraction

Thyroid Gland

Thyroid Hormone

Most Cells Of The Body

Regulates metabolism and has a corresponding impact on development, maturation, nervous system activity, and metabolism


Primarily Bone

Reduces rate of bone decomposition and prevents the increase in calcium ions in the blood.

Parathyroid Gland

Parathyroid Hormone (PTH)

Bone, Kidney

a key factor in controlling blood calcium levels

Adrenal Gland


Blood Vessels, Liver, Heart, Fat Cells

Increases blood flow, heart rate, and oxygen intake.


Blood Vessels, Liver, Heart, And Fat Cells

Regulate blood pressure


Kidneys, Sweat Glands, And Intestine

regulates blood pressure, water balance, and salt levels.


Most Tissues

controls important bodily processes, reduces inflammation, keeps blood sugar, blood pressure, and muscular strength stable, and manages salt and water balance.

Pancreas, more specifically Islets of Langerhans


Liver, Skeletal Muscle, Adipose Tissue

lowers blood sugar levels and accelerates protein, lipid, and glucose metabolism


Primarily Liver

Increases blood sugar level



Immune Cells/Tissues

Helps in the development and proper functioning of the immune system

Pineal Gland


Hypothalamus And Many Other Tissues

releases melatonin during the night to promote sleep



Most Tissues

vital for the health of the uterus and breasts, has an impact on the development of female sexual characteristics and maintains bone health.


Most Tissues

stimulate uterine lining for conception and get the breasts prepared for producing milk



Most Tissues

enhancement of male sexual characteristics and maturation


Gonadotropin-releasing hormone (GnRH)

Pituitary Gland

controls the release LH/FSH from the pituitary gland.

Corticotropin-releasing hormone (CRH)

Pituitary Gland

controls the release of adrenocorticotropic from the pituitary gland.

Thyrotropin-releasing hormone (TRH)

Pituitary Gland

controls the release of thyroid-stimulating hormone from the pituitary gland.

Growth hormone-releasing hormone (GHRH)

Pituitary Gland

controls the release of growth hormone from the pituitary gland.

What Are Hormones Made Of?

Hormones are made of a diverse range of chemicals, but they are classified into three classes –

  1. Eicosanoids

  2. Amino acid/protein derivatives (amines, proteins, and peptides)

  3. Steroids

Important Hormones of the human body

  • Melatonin: It primarily controls the circadian rhythm or sleep cycles.

  • Estrogen: This is the main sex hormone present in women which bring about puberty, prepares the uterus and body for pregnancy and even regulates the menstrual cycle. Estrogen level changes during menopause because of which women experience many uncomfortable symptoms.

  • Cortisol: It has been named the “stress hormone” as it helps the body in responding to stress. This is done by increasing the heart rate, elevating blood sugar levels etc.

  • Progesterone: It is a female sex hormone also responsible for the menstrual cycle, pregnancy and embryogenesis.

  • Testosterone: This is the most important sex hormone synthesized in men, which cause puberty, muscle mass growth, and strengthen the bones and muscles, increase bone density and controls facial hair growth.

Some hormones, such as serotonin and dopamine, also function as neurotransmitters, which are chemicals that relay messages between nerve cells in the brain and from neurons to muscles.

How Many Types of Hormones are There in a Human Body?

Even though there are several types of hormones in a human body, they are primarily classified into three categories based on their chemical structure. These are –

  1. Lipid-Derived Hormones

Lipid-derived hormones are primarily derived from cholesterol, and they share a similarity in terms of their structure. Steroid hormones are the primary lipid hormones in the human body, and chemically they are either ketones or alcohols. Examples of steroid hormones are cortisol and aldosterone.

  1. Amino Acid-Derived Hormones

These classes of hormones originate from amino acids, tyrosine and tryptohan. Examples of such hormones as norepinephrine and epinephrine. The medulla section of the adrenal glands produces these. Moreover, the pineal gland in the brain synthesizes melatonin, which controls the sleep cycle.

  1. Peptide Hormones

The structure of the peptide hormone is similar to that of the polypeptide chain (chain of amino acids). A popular example of peptide hormone is insulin produced by the pancreas.

Name of Hormones and Their Functions

Here is a list of some important hormones and their functions –

  • Insulin: Produced by the pancreas, this hormone helps the human body to synthesize glucose from food intake for energy. Additionally, it controls the blood sugar level in the human body.

  • Cortisol: It is a steroid hormone synthesized in the cortex of adrenal glands. Furthermore, this hormone is also called stress hormone as it helps the human body to deal with any pressure.

  • Melatonin: The pineal gland in the human brain produces this hormone. It primarily controls the sleep cycle.

  • Progesterone: This female hormone is responsible for embryogenesis, menstrual cycle, and pregnancy. It is produced in the corpus luteum section of the ovary.

Examples of Hormones

  • Insulin is a hormone that's made by the beta cells in the pancreas. When it is released into the blood, insulin helps regulate how the cells of the body use glucose (a type of sugar) for energy.

  • Androgens are responsible for male sex characteristics. Testosterone, the sex hormone produced by the testicles, is an androgen.

  • Estrogens are the group of hormones responsible for female sexual development. They are produced primarily by the ovaries and in small amounts by the adrenal glands.

  • The thyroid gland secretes two main hormones, thyroxine and triiodothyronine, into the bloodstream. These thyroid hormones stimulate all the cells in the body and control biological processes such as growth, reproduction, development, and metabolism.


The existence of humans depends heavily and fundamentally on hormones. Having too little or too much of a certain hormone might have negative health effects, even though your body generally carefully manages its hormone levels. Diabetes, including Type 1 diabetes, Type 2 diabetes, and gestational diabetes are a few of the most prevalent hormone-related illnesses.

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FAQs on Hormones

1. What is meant by hormones? Why are hormones called chemical messengers?

Hormones are chemical substances released by various endocrine glands to regulate the functions of various organs of the human body. Additionally, hormones are called chemical messengers because they convey the signal which causes an organ or tissue to perform a definite action. Hormones are called chemical messengers because they are chemical agents that travel around the body to tell specific cells to perform a specific action. The term hormone describes a variety of chemicals that perform these signaling tasks. Hormones can range from proteins to amino acids to steroids.

2. Where are hormones made in the human body?

The human body secretes and circulates some 50 different hormones. A wide variety of these chemical substances are produced by endocrine cells, most of which are in glands.  Hormones are made in different endocrine glands within the human body. Some of the prominent glands are the hypothalamus, pituitary, thyroid, pineal, pancreas, adrenal, etc. After synthesizing, these hormones are released into the blood. Various tissues of the body secrete hormones into fluids, like blood. From there, the hormones travel far from the place they were made until they reach cells that read the chemical as an instruction.

3. How many types of hormones exist in the human body?

Communication between neighbouring cells, and between cells and tissues in distant parts of the body, occurs through the release of chemicals called hormones. The human body carries Several types of hormones. However, they are classified into three main groups as per their chemical structure. These are lipid-derived hormones, amino acid-derived hormones, and peptide hormones. One of the key distinguishing features of lipid-derived hormones is that they can diffuse across plasma membranes whereas the amino acid-derived hormones and peptide hormones cannot diffuse across plasma membranes.

4. How do Hormones Work?

When a hormone diffuses outside of a capillary, it can act on a target cell – a cell with receptors that correspond to it. There are two types of hormonal activity. Asteroid hormone is capable of crossing through the cell membrane of the target cell. It unites with a receptor protein located inside the nucleus, which stimulates or blocks the cell’s genetic activity. A protein hormone cannot penetrate the target cell. It attaches to the cell’s membrane and activates a receptor that releases, in turn, a messenger within the cell.

5.  Where can I get a thorough understanding of hormones?

Vedantu has provided here a thorough explanation of hormones by featuring the definition of hormones, what the factors of 81 are, how students can find them and list out the factor pairs of 81 for them to prove the calculation works along with the relevant examples and stepwise methods. On Vedantu, the concept of Factors of 81 has been compiled in an easy-to-understand manner to help students learn the concept of Factors of 81 with ease. Students can learn the concepts of all the important topics of Mathematics on Vedantu.

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