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Hormones in Animals

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IVSAT 2024

Compared to plants, animals are more complicated. They have a variety of useful organs that carry out specific functions for their coordination and control. For this connection (Endocrine System), nerve coordination (Neural System), as well as chemical coordination in animals, are responsible. To control the numerous bodily functions in animals, both of these systems work in a coordinated way.

Hormonal coordination acts as the chemical mediator for multicellular existence, which directs everything from routine maintenance to reproduction and development. They are a group of mostly unique chemical messengers that are released by the nerves, normal tissue, or specific glands. Hormones affect the cells that are located far away from the point of their release. They may be proteins, distinct polypeptides, steroids, amines, or different types of lipids.

The circulatory system carries hormones to their site of action, where they ultimately bind to a specified receptor molecule which is either linked to a cell membrane or, more commonly, found inside the cell, depending on the receptor's design. The hormones coordinate almost everything, while the nervous system controls the faster-moving functions of animal life, such as locomotion.

What are Hormones in Animals?

Several endocrine glands and hormones make up the endocrine system. Animals' endocrine glands aid in the coordination of chemicals. They release compounds called hormones. In comparison to plants, hormones in animals are regularly made in specialised glands that manufacture hormones.

The hormones are subsequently produced from the glands. After entering the bloodstream, they are carried all across the body and function to control different metabolic processes. Our body has two distinct hormonal coordination systems, such as:

  • The exchange of hormones between two endocrine glands: One gland secretes a hormone, which triggers the release of another gland's hormones at a different level.

  • The connection of an endocrine gland with a target organ: The target cells have certain receptors to identify the corresponding hormones.

Different Types of Hormones and Their Function

All organs are under the command of hormones. The functions of hormones involve coordination of variety of systems, including sexual aspects, reproduction, growth and development. Extremely little hormones can cause the body to react in very apparent ways. The endocrine glands in animals secrete approximately 20 major types of hormones into the bloodstream, which are important for numerous biological processes of the body. The table below lists different hormones and their functions, along with their types and the glands that produce each one.





Gonadotropin-releasing hormone (GnRH)

Promotes the release of gonadotropins from the pituitary gland.



Controls the body's metabolism.

Pituitary Gland

Growth hormone

Controls body growth.

Adrenal Gland


Influences blood pressure and heart rate.


Insulin and Glucagon

Controls blood sugar levels.



Production of sperm and the development of male characteristics.


Oestrogen and Progesterone

Production of the ovum and feminine characteristics.

Classification of Hormones in Animals

Hormones can be classified into the following groups based on their chemical composition:

Steroid Hormones

These hormones, which are produced from cholestrol and lipids, attach to proteins as they travel through the bloodstream and typically cause activation of the formation of new proteins as their targeted response. Chemically, they are typically ketones or alcohol. For instance, the female and male reproductive systems, respectively, secrete the hormones oestrogen and testosterone. Water does not dissolve steroid hormones. Compared to peptide hormones, steroids remain for a longer duration because they are delivered by the blood transport proteins.

Protein/Peptide Hormones

These hormones are made up of interlinked amino acid polypeptide chains. The secretory vesicles are where the peptide hormones are created and preserved. They are located in the cell membrane and are exocytosis out of the parent cell.

Examples include brain-synthesized hormones like oxytocin, vasopressin, and ADH (antidiuretic hormone), which are secreted into the bloodstream through the posterior pituitary gland. It also comprises the major glycoproteins like the FSH (follicle-stimulating hormone) and growth hormones produced by the pituitary. These hormones are water soluble but insoluble in lipids.

Amino-Acid-Derived Hormones

Amino-acid-derived hormones are relatively smaller molecules made of the amino acids: tryptophan and tyrosine. The adrenal gland secretes norepinephrine and epinephrine, also referred to as catecholamines. The pineal gland, which is located in the brain and is in-charge of regulating the sleep-wake cycle, secretes melatonin.

Importance of Hormones

Human existence depends on hormones, which are both significant and necessary. Hormonal imbalances brought on by having too little or too much of a particular hormone can result in numerous health complications, including diabetes, obesity, infertility, and more. Hormones serve as unique messengers that regulate various biological functions, such as hunger, body temperature, mood, growth, and others. Additionally, human behaviour is controlled by hormones that work in conjuction with the nervous system of the body.

Interesting Fact

Not every hormone activates every cell in the body. Instead, only the cells that carry a certain hormone's receptors, often known as target cells, can directly be affected by a specified hormone.

Key Features

  • Endocrine glands are specialised glands that manufacture and release hormones, which are organic chemical messengers.

  • Stress, infections, blood minerals, and other factors can all have an influence on the levels of hormones in animals.

  • The hormones are produced at various locations, functioning at various spots. Despite the fact that different types of hormones are present in the bloodstream, each hormone primarily affects its target organ.

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FAQs on Hormones in Animals

1. Why is it advised to use iodized salt?

Iodine stimulates the thyroid gland's production of the hormone thyroxine. Therefore, it is recommended to consume enough iodine for healthy thyroid gland activity.

2. What do the stress and pleasure hormones do?

Dopamine, also known as the ‘happy hormone,’ is a chemical that is released when we enjoy something. Cortisol, or ‘stress hormone,’ is higher in our blood when we feel stress.

3. Can prolactin interfere with sleep?

Yes. One of the growth hormones that affect sleep and encourages rapid eye movement sleep is prolactin.

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