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Hormones - Functions, Types, and Mechanism of Action

Published on Sep 22, 2022 and last reviewed on Oct 10, 2022   -  4 min read


Hormones are a group of signaling molecules secreted by glands that do physiological activities and maintain homeostasis in the body. Read further to know more.


Hormones are the body’s chemical messengers; they travel in the bloodstream to various organs and tissues. These hormones carry out multiple physiological functions in the body. Endocrine glands are majorly responsible for the production of hormones. There are different types of hormones for specific functions in the body, and they are produced by different kinds of endocrine glands. Any imbalance in the levels of hormones can lead to serious health issues.

What Are Hormones?

Hormones can be defined as a group of signaling molecules in multicellular organisms that are transported to distant cells and organs through complex biological processes to regulate physiology and behavior in the body. These hormones act as chemical messengers in the body that are carried by the bloodstream to different parts of the body, which interpret these messages and act on them accordingly. Hormones carry out their functions by evoking responses from specific organs or tissue that are adapted to react to them. Hormones work slowly, over time, and affect the body’s growth, development, metabolism, sexual functioning, and mood. When the endocrine glands underproduce (or do not produce at all) or overproduce a hormone, multiple diseases are caused.

What Do Hormones Do?

Hormones are vital for the proper functioning of the body, and they carry out a lot of crucial functions in the body. The various functions of the hormones include:

How Do the Hormones Work?

The actions of hormones are carried by the blood throughout the body. But specific hormones affect specific cells; these specific cells have receptor sites for that hormone. The mechanism of action of hormones is in the form of a lock and key mechanism. If the hormone fits the receptor site like a key, then only there will be an effect. If the hormone and the receptor site do not match, then there will be no outcome. In some cases, the target tissue is localized and limited to a certain gland or organ. Whereas, in some cases, the target tissues are diffused and present throughout the body, and therefore, many areas are affected.

Hormones bring about their characteristic effect by modifying cellular activity. In addition, protein and steroid hormones react with the receptor differently. The protein hormones react with the receptor on the surface of the cell, and the resulting hormone action is relatively fast. The steroid hormones react with the receptor inside the cell; this is a relatively slow process because it involves the synthesis of protein.

What Are the Types of Hormones?

Hormones can be chemically classified into four groups:

  1. Amino Acid Derived: These are hormones that are modified amino acids.

  2. Polypeptides and Proteins: These hormones are a chain of amino acids; the chain may be less or more than one thousand amino acids long.

  3. Steroids: These hormones are lipids that are synthesized from cholesterol; steroids are characterized by four interlocking carbohydrate rings.

  4. Eicosanoids: These hormones are lipids synthesized from fatty acid chains of the plasma membrane.

Hormones activate the target cells by different mechanisms, depending upon the chemical nature of the hormone. Therefore, based on these criteria, hormones are classified as:

  1. Lipid-Soluble: Basically, steroid and thyroid hormones are lipid-soluble hormones. These hormones diffuse through the cell membrane of the target cells and then bind to the receptor protein, leading to the activation of a DNA segment that turns on specific genes.

  2. Water-Soluble: Proteins, polypeptides, and amino acid hormones are water-soluble hormones. These hormones bind to the receptor protein on the plasma membrane of the cell. The receptor protein, in turn, stimulates the production of secondary messengers.

What Are the Major Hormones in the Body and Their Function?

Hormones in the Body - Chemical Class - Steroids

Hormones in the Body - Chemical Class - Peptide

Hormones in the Body - Chemical Class - miscellaneous


Hormones are the chemical messengers of the body that are carried through the blood to the different parts of the body to carry out specific functions. Hormones are responsible for a wide range of actions in our body, from growth and development to reproduction, response to stress, etc. Therefore, hormones are crucial for a healthy body and life; any imbalance in the levels of the hormones can cause various disorders. Conditions like hypothyroidism, hyperthyroidism, Cushing’s disease, Conn’s disease, infertility, complete androgen insensitivity, depression, etc. Therefore, maintaining the correct level of hormones in the body is crucial.

Last reviewed at:
10 Oct 2022  -  4 min read




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