What is the Difference Between Prostaglandins and Hormones

The main difference between prostaglandins and hormones is that the prostaglandins are involved in triggering inflammation and formation of a blood clot at the site of tissue injury whereas the hormones are the main type of regulatory molecules of growth and development, metabolism, and reproduction.

Prostaglandins and hormones are two types of regulatory molecules in the body. Prostaglandins are lipid molecules, which act as hormones while hormones are either proteins, peptides or steroids.

Key Areas Covered

1. What are Prostaglandins
     – Definition, Structure, Function
2. What are Hormones
     – Definition, Structure, Function
3. What are the Similarities Between Prostaglandins and Hormones
     – Outline of Common Features
4. What is the Difference Between Prostaglandins and Hormones
     – Comparison of Key Differences

Key Terms

Endocrine, Hormones, Inflammation, Paracrine, Prostaglandins, Proteins

What are Prostaglandins

Prostaglandins are the group of hormone-like molecules mainly produced by animals. They are small fatty acids produced by each and every nucleated cell in the body. These fatty acids are made up of 20 unsaturated carbon molecules, including a 5-carbon ring. Arachidonic acid is the precursor molecule for prostaglandins.

Figure 1: Prostaglandin A1

The main function of prostaglandins is to serve as chemical signaling molecules, which act on the nearby cells. Hence, they are paracrine molecules. The functions of prostaglandins are as follows.

1. Initiation of the inflammatory response and the production of fever, and pain in tissue damage. Prostaglandins are produced as a result of white blood flow to the site of tissue injury.
2. Formation of a blood clot in a damage to blood vessels. Thromboxane is the type of prostaglandin which activates the formation of blood clot.
3. Induction of the labor. Prostaglandins like PGE2 are responsible for the uterine contractions, which induce labor.
4. Prostaglandins have functions in other systems including the gastrointestinal tract, kidney, and bronchi.

What are Hormones

Hormones are the main type of regulatory molecules in the body produced by the endocrine glands. They are secreted to the bloodstream and transported to the effector organs through the blood. They can be either proteins, peptides or steroids. Some amino acid derivatives act as hormones as well. Most hormones including pituitary hormones, insulin, and secretin are peptide hormones. Male and female sex hormones are steroids. Thyroxine and adrenaline are amino acid derivatives, which act as hormones.

Figure 2: Hormones

Small amounts of hormones are effective in the body in very few concentrations. Steroid hormones can diffuse into the cell; hence, their receptors occur inside the cell. On the other hand, the receptors for the protein or peptide hormones occur on the cell membrane. Some plant hormones act on the site of production while others are transported to the site of action through the sap.

Similarities Between Prostaglandins and Hormones

• Prostaglandins and hormones are two types of small molecules produced by the body.
• They regulate various functions of the body.

Difference Between Prostaglandins and Hormones

Definition

Prostaglandins refer to any of a group of compounds with varying hormone-like effects, notably the promotion of uterine contractions while hormones refer to the regulatory substances produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action. Hence, this is the fundamental difference between prostaglandins and hormones.

Occurrence

Another difference between prostaglandins and hormones is that the prostaglandin-like compounds occur in plants while the hormones occur in both animals and plants.

Made up of

Moreover, prostaglandins are lipid molecules while proteins can be either proteins, peptides or steroids.

Production

Also, most nucleated cells in the body produce prostaglandins while hormones are produced by the endocrine glands.  

Mechanism of Action

A major difference between prostaglandins and hormones is their mechanism of action. That is, prostaglandins are paracrine molecules that act on the nearby cells while hormones are endocrine molecules which act as a distinct part of the body by being transported through the blood or sap. This is

Function

Their functions also contribute to another difference between prostaglandins and hormones. Prostaglandins are involved in the contraction and relaxation of smooth muscles, and modulation of inflammation while hormones regulate various functions of the body including growth, development, metabolism, and reproduction.

Examples

Some examples of prostaglandins are prostaglandin B, E, A, and F while some examples of hormones include estrogen, testosterone, insulin, auxin, and gibberellin.

Conclusion

Prostaglandins are hormone-like molecules which induce several functions in the body including inflammation. They act as paracrine molecules. Hormones are the main regulatory molecules of the body produced by endocrine glands. They are transported through the blood to the site of action. The main difference between prostaglandins and hormones is their structure and mechanism of action.

Reference:

1. “Prostaglandins.” Aluminum, Available Here
2. Nussey S, Whitehead S. Endocrinology: An Integrated Approach. Oxford: BIOS Scientific Publishers; 2001. Chapter 1, Principles of endocrinology. Available Here

Image Courtesy:

1. “Prostaglandin A1 Structural Formula V1” By Jü – Own work (Public Domain) via Commons Wikimedia  
2. “Hormone” By संताजी बबन चवरे –  (CC BY-SA 4.0) via Commons Wikimedia