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What are Hormones? Types, Functions and Hormonal Diseases

Jul 7, 2022

Hormones Definition

Hormones are defined as some type of chemicals that are synthesised and created by the specialised glands in our bodies. They can control and regulate the activities performed by various organs and cells. We call these specialised glands endocrine glands.

Hormones are like chemical messengers of our bodies. They are capable of travelling in our bloodstream to organs and tissues. The working of hormones is very slow and time-consuming, but it may have impacts on the following things in our bodies:

  • Mood
  • Sexual function
  • Reproduction
  • Growth & development
  • Metabolism

Hormones are very powerful and determine how we appear both physically and mentally. This article will discuss everything associated with hormones while having a brief look at other related concepts.

What are hormones?

As mentioned before, we can classify hormones as chemicals whose fundamental purpose is to act as messengers of our bodies. Special glands are used for the secretion of hormones. These special glands are called endocrine glands. Endocrine glands are present in the whole of our bodies.


Furthermore, these messengers are highly capable of controlling various physiological and psychological functions. Hormones are essential in order to maintain homeostasis in the body.

Signalling of Cells

Hormones’ effects are solely based on the way they are released. The following are the categorisation of signalling effects:

  1. Endocrine: Endocrine is the hormone that acts on the target cells after it gets released from the glands into the bloodstream.
  2. Intracrine: Intracrine is the hormone that is produced in the cells. It can act intracellularly, which indicates it can act inside the cells.
  3. Paracrine: Paracrine is one type of hormone that acts on nearby cells. It does not require entering the blood circulation.
  4. Autocrine: Autocrine is the hormone that can act on the cell that secreted it.

Types of Hormones

Various types of hormones are produced in order to regulate multiple functions. Following is the classification of hormones:

  • Steroid hormones
  • Peptide hormones

1. Steroid hormones

Steroid hormones are considered fat-soluble hormones. They are capable of passing through a cell membrane. Some examples of steroid hormones include testosterone, progesterone and estrogen. These are regarded as sex hormones.


2. Peptide hormones

Unlike steroid hormones, these are made up of amino acids. These are water-soluble and cannot pass through the membrane of the cell. The reason is the presence of a bilayer of phospholipid that could stop non-dissolving fat molecules as they try to diffuse into the cell. An ideal example of peptide hormones is insulin produced by the pancreas.

List of essential hormones

In our bodies, various hormones are present. These hormones are essential for performing specific tasks. Let us see what they are:

  1. Melatonin

The primary function of melatonin is to control the sleep cycles or the circadian rhythm.

  1. Cortisol

The other name of cortisol is the stress hormone. It is because it assists the body in responding to stress. The function of cortisol involves elevating blood sugar levels, enhancing the heartbeat rate, etc.

  1. Testosterone

Testosterone is considered the most vital sex hormone. This hormone is synthesised in men. Some of its causes are muscle mass growth, causing puberty, a rise in the density of the bones, strengthening the muscles and bones, controlling facial hair growth, etc.

  1. Estrogen

Estrogen is regarded as the main sex hormone contained in women. It can cause puberty, helps prepare the body and uterus for pregnancy, regulate the menstrual cycle, etc., and the level of estrogen can change during menopause. It is because women experience various unpleasant symptoms.

  1. Progesterone

Progesterone is another type of female sex hormone which is also responsible for the occurrences of pregnancy, menstrual cycle and embryogenesis.

Hormone Secretion

Endocrine glands are very different from other glands. This gland is helpful in releasing hormones. They are considered ductless. 

Below provided are the different types of organs that perform various tasks:

  • Pineal gland: The other name for pineal is the thalamus. It is capable of producing serotonin derivatives of melatonin. It can affect sleep patterns.
  • Hypothalamus: Hypothalamus is responsible for controlling the temperature of the body, hunger, thirst, regulating emotions, moods, sleep and enabling hormone production.
  • Thyroid: The thyroid gland can produce hormones that could influence how calories are burnt and the rate of the heartbeat.
  • Parathyroid: Parathyroid gland helps control the calcium content present in the body.
  • Thymus: The thymus enables T-cell production and helps the adaptive immune system function.
  • Adrenal: Adrenal is the gland that is responsible for producing the hormones that could control stress hormone, cortisol and sex drive.
  • Pancreas: Pancreas is an essential gland because it is responsible for producing insulin hormones. Insulin plays a vital role in maintaining the sugar level in the blood.
  • Pituitary: The pituitary gland is the master control gland. The reason is that it majorly helps control other glands. Furthermore, the pituitary gland can enhance hormones which could possibly trigger growth and development.
  • Testes: Testes are responsible for secreting sex hormones in men. This hormone is called testosterone. In addition to that, testes also produce sperm.
  • Ovaries: Ovaries are present in the female reproductive system. It is responsible for releasing female sex hormones, namely progesterone, estrogen, and various other hormones.

Functions of Hormones

Below mentioned are some of the essential functions performed by various hormones:

  • Having hormones in the body can help control frequent hunger and thirst.
  • Hormones are highly responsible for maintaining body temperature.
  • The main function of hormones is to engage in the growth and development of the body. 
  • Another major function of hormones includes food metabolism.
  • Hormones mainly help regulate mood and cognitive functions.
  • Hormones play a vital role in initiating and performing sexual development and reproduction.

Hormonal Diseases

Endocrine malfunction can cause various hormonal diseases. Common hormonal diseases are usually incorporated with the adrenal, hypothalamus and pituitary glands. Imbalanced secretion of these hormones is capable of affecting growth, development and metabolism.

Furthermore, diseases like diabetes, osteoporosis and hyperthyroidism can be caused because of hormonal imbalance. The following are a few factors that are responsible for hormonal diseases:

  • Environmental
  • Genetic
  • Diet-related 

Feedback Mechanism of Thyroid Gland

Thyroxine is a hormone produced by the thyroid gland. The secretion can be easily controlled by the TRH (Thyrotropin Releasing Hormone) from the TSH (Thyroid Stimulating Hormone) and the hypothalamus from the anterior pituitary.

When thyroxine level in the blood is reduced, the hypothalamus is responsible for stimulating the secretion of the thyroid by TSH secretion stimulation. This process denotes the positive feedback mechanism.

Furthermore, when the hypothalamus starts to stimulate the production of thyroxine, it will possibly lead to a high-level thyroxine secretion in the blood. It further sends the negative feedback to the hypothalamus in order to stop or reduce the TSH and TRH secretion that can regulate the level of thyroxine in the body. This mechanism is termed a negative feedback mechanism.

In addition, hormones are generally secreted for their target tissues so that they can perform specific functions. Once the hormones have met their targets, they are no longer needed, so they are removed. Organs such as kidneys and liver do this often.

The following is the diagrammatic representation of the feedback mechanism of the thyroid gland:


All in all, hormones are the deciding factors in our bodies as they are responsible for allowing multiple tasks to be carried out. It is very important to know how hormones react in our bodies. From this blog, we have understood the hormone definition, signalling of cells and hormone types while having a good look at the list of essential hormones in the body.

Furthermore, we have also seen how hormones are secreted, how they function and what diseases will be caused due to hormonal imbalance.

Frequently Asked Questions

What is a hormone?

A hormone is a chemical whose sole responsibility is to control and regulate the activities performed by multiple organs and cells. Endocrine glands generally secrete the hormones. Endocrine glands are seen as ductless glands.

Mention the organs present in the endocrine system.

The endocrine system consists of various organs. Let us see what they are:
1. Hypothalamus
2. Thymus
3. Parathyroid
4. Pineal
5. Thyroid
6. Pituitary
7. Adrenal
8. Pancreas
9. Ovaries
10. Testes

What do hormones do?

Hormones are capable of carrying out various functions. The following are some of the most important ones:
1. They maintain body temperature
2. They control hunger thirst
3. They play a key role in growth and development
4. They regulate cognitive functions
5. They help in food metabolism
6. They initiate and maintain sexual development and reproduction

What are Hormones


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