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
Protein HormonesSteroid HormonesAmino acid derivatives (tyrosine) hormones
Insulin and Glucagon-Maintain blood glucose concentrationCortisol- Provides anti-stress response and anti-inflammatory response and maintains glucose concentration
Antidiuretic hormone or Vasopressin-Maintains salt and water balance in the body
Prolactin- Helps breasts to grow in size and lactate during pregnancy and after birthOestrogen and Progesterone- Female sex hormones that help in reproduction and regulate the menstrual cycleThyroxine-Plays a role in the functioning of the heart and digestive system, as well as muscle control, and development of brain and bone health
Gastrin- Helps with the churning of food in the stomach and releases hydrochloric acid that digests proteins and kills harmful bacteriaTestosterone- Male sex hormones that help in secondary sexual trait development during puberty and reproductionAdrenaline, Noradrenaline and Dopamine-Act in flight, fight or freeze responses
Parathyroid Hormone- Regulates calcium levels in the body through its release, absorption and conservationSerotonin- Regulates mood, sleep and sexual desire
Follicle-stimulating hormone (FSH) and Luteinising hormone (LH)-Help maintain reproductive function in people assigned female at birth (AFAB)Melatonin- Helps in regulating our 24-hour inner clock or circadian rhythm 

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 


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


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. 


  1. Tata JR. One hundred years of hormones. EMBO Rep [Internet]. 2005 Jun [cited 2023 Feb 23]; 6(6):490–6. Available from:
  2. McLaughlin MB, Jialal I. Biochemistry, Hormones. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 [cited 2023 Feb 23]. Available from:
  3. Campbell M, Jialal I. Physiology, Endocrine Hormones. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 [cited 2023 Feb 23]. Available from: 
  4. News-Medical. Chemical Classes Of Hormones [Internet]. 2009. Available from:
  5. Steroid - Biological significance of steroids [Internet]. Encyclopedia Britannica. Available from: 
  6. ‌Protein - Protein hormones [Internet]. Encyclopedia Britannica. Available from: 
  7. ‌Newton AC, Bootman MD, Scott JD. Second Messengers. Cold Spring Harb Perspect Biol [Internet]. 2016 Aug [cited 2023 Feb 23]; 8(8):a005926. Available from: 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Kanisha Mehta

Master of Science in Biomedical Sciences (Immunology) at the University of Westminster, Bachelor of Dental Surgery (BDS), Saurashtra University, India

I am Kanisha, a graduate biomedical researcher and a former dentist. As a health professional, I have read, written, heard, and seen many stories of patients going through an array of ailments such as oral diseases, cancers, and nutritional deficiencies and I consider it a moral duty to spread awareness regarding this ailment which starts off small and turns up taking a bigger picture. I hope with this piece of article you could make the right choice of steps needed to be taken for prevention and cure. presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
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