How do hormones work?

The role of a hormone is one of a chemical messenger in the human endocrine system (hormonal system). Produced by specific glands and organs in the body, hormones are secreted into the blood and other body fluids. The majority of hormones are transported to the circulatory system to other areas of the body, where they influence specific organs and cells. Hormones are in charge of the regulation of many biological activities including growth; development; reproduction; the use of energy and its storage; electrolyte and water balance.


How hormones work in the body is that they function as chemical messengers, delivering instructions to particular parts of the body. 

  • Hormones only have the ability to affect cells that display receptors that are unique to them.
  • Cells can display receptors for multiple hormones at one time.
  • If a cell shows more receptors for a particular hormone, the cell will be more sensitive to that hormone and the messages it sends.
  • Up-Regulation is when a cell displays more receptors in response to a hormone
  • Down-Regulation is when a cell reduces its number of receptors for a particular hormone
  • A hormone can make changes to a cell directly by altering what genes are activated
  • A hormone can make changes indirectly to a cell by stimulating specific signalling pathways inside the cell that affect other processes.
  • Cells are influenced by a hormone when they express a receptor for that hormone.
  • Depending on the location of the protein receptor on the target cell and the chemical structure of the hormone, hormones can mediate changes directly by binding to intracellular hormone receptors and modulating gene transcription, or indirectly by binding to cell surface receptors and stimulating signalling pathways.


What are the types of hormone signalling?

Signalling mechanisms that occur in multicellular organisms are autocrine, paracrine, endocrine and direct signalling.

Hormones circulated in the blood will come in contact with various cells. The cells that they choose to communicate with however are specific target cells.

What are target cells?

Target cells are those who have receptors for a particular hormone.

What are target cell receptors?

Target cell receptors can be found on the surface of the cell membrane. They can also reside within the cell.

Endocrine Signalling

When a hormone binds to a target cell receptor, it creates changes within the cell. This, in turn, influences the function within the cell.  Hormone signalling that occurs in this manner is called “endocrine signalling”. The reason for this is that the hormones affect target cells over an area or distance.

Paracrine Signalling

Hormones have the capability to impact isolated cells alongside that of neighbouring cells. Hormones act on local cells through secretion into the interstitial fluid that surrounds the cells. These hormones will then diffuse to nearby target cells. This type of signalling is described as “paracrine signalling”.

Autocrine Signalling

In autocrine signalling, hormones do not travel to other cells but cause changes in the same cell that release them.

Direct Signalling

Direct signalling occurs by transferring signalling molecules across gap junctions between neighbouring cells.

What are the types of hormones

The Hormonal System and how it relates to peptides
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