Are Hormones Proteins?

Hormones make up terminology that is often used by us when conditions inside the body suddenly trip, such as the premenstrual phase, having a dopamine kick, and the rise of happy hormones. However, several questions arise, such as what are these molecules, what are they made up of, how do they function and why they are so important to us.

These molecules are just complex chains of amino acids that form peptides/proteins. However, some of them are made up of fatty acids as well. They generally follow orders given by the brain to provide a response to a condition that has stimulated the body internally and externally. This is so that normal functioning is maintained.

Hormones are the chemical messengers that link basically every biological mechanism of the body, and if there is any deficiency due to genetic or environmental reasons, the deficient hormone needs to be replaced using hormonal replacement therapy under the guidance of a GP and specialist.

Understanding hormones

In June 1905, at University College London, a physiology professor named Ernest Starling referred to the term “hormones”. These hormones were defined as chemicals that acted as messengers travelling around the body from one cell to another through blood vessels,while coordinating various activities and helping with the growth of different parts of the body. Further research and studies were carried out on how these molecules were released, their modes of function, their action in physiological processes, and their role in shaping different pathologies. 

These molecules are vital in the body because they maintain homeostasis, and regulate development, reproduction, and metabolic demand. These molecules are released by various organs and glands, altogether forming endocrine systems in the body that are under the nervous system's control. This interplay between the nervous and endocrine systems determine the internal stimulus and external conditions that can disturb the normal state of the body and work in a feedback mechanism to maintain the normal state of the body. Hence, if something shoots up or drops down, the hormones come into action through a message delivered by the brain or spinal cord, and thus bring the concentration of different chemicals and molecules back to a steady state.

The discovery of the mechanism of action of hormones led to a revolution in the field of medicine as it was now possible to target them in order to bring diseased conditions back to normal functioning. These molecules are activated by other molecules, referred to as ligands, which then bind to receptor proteins on the surface of cells and trigger signalling inside the cell, which eventually leads to the activation of hormones. Thus, it was now possible for researchers to study its pattern and make medicines that would target these regions and enable the normal functioning of the body.¹

Types of hormones

The composition and microscopic build of the hormones led to their classification, and thus, they can be grouped into three categories:^{2, 3, 4, 5}

1. Protein or peptide hormones
2. Steroid hormones
3. Amino acid or tyrosine derivatives

Are hormones type of proteins

If so, what is the purpose and importance?

Through years of research and analysis, some hormones are classified as protein or peptide hormones. Peptides are made up of long chains of amino acids that collectively form the building blocks of proteins. Protein hormones possess the enzymatic activity that helps in carrying out various chemical reactions to maintain the normal physiologic state of the body. Also, apart from the types of hormones and their respective functions depicted in the table, these proteins participate in the synthesis or making of steroid hormones.^{4 6}

If not, what are the differences?

As stated, some of the hormones are steroid derivatives that are composed of fatty acids or lipids. These cholesterol derivatives are released from three steroid glands which are the cortex, the testes, and the ovaries (inclusive of the placenta during pregnancy), and play a vital role in stress responses and human reproduction.⁵ 

FAQs

Which is not a protein hormone?

All steroid hormones are not protein hormones, such as cortisol, and sex hormones, such as oestrogen, progesterone, and testosterone.

Can proteins act as hormones?

Messenger proteins, such as growth hormones, act as secondary messengers or signalling molecules in carrying out important cell signalling mechanisms. These signalling cascades are important as they determine the release of chemicals from a particular organ or site, at the right time and in the right conditions. The mechanism of action of these proteins is as follows. 

These molecules help in broadcasting the message that is received from the ligand when it binds to the receptor on the cell membrane. Later, these messengers diffuse into the target areas of cells and alter the activities in response to the message that has been received from the type of ligand-receptor complex.⁷

Summary

All in all, it can be said that some hormones are proteins, and some proteins are hormones, through their mechanisms of action in cells, forming links across the nervous and endocrine systems, and regulating homeostasis in the body for healthy living.