Peptide Hormones List: Overview, Functions, and Examples

May 9, 2025

Does your stomach grumble before lunchtime, or do your energy levels fluctuate throughout the day? While your surroundings and lifestyle certainly play a role, the silent drivers of these experiences are hormones, those tiny chemical messengers working continuously within your body.

Within this intricate network lie peptide hormones, which are key to many essential processes.

This blog will explore peptide hormones and their functions and workings. We will also introduce you to a list of peptide hormones in your body—some of which you might already be familiar with.

So, get ready to appreciate the unseen commanders that keep your life balanced, energetic, and resilient!

What are peptide hormones?

Peptide hormones are small molecules built from short chains of amino acids, the fundamental building blocks of proteins. Typically, they are composed of anywhere between 2 to 100 amino acids. These hormones act as vital signals, instructing various cells and tissues throughout your body to perform specific tasks.

Peptide hormones are naturally produced by various endocrine glands in your body. Being water-soluble, they can easily travel through your bloodstream to reach their target destinations.

These hormones are stored within the cell in membrane-bound sacs called secretory vesicles. This allows for a rapid and controlled release when the body needs the hormone's specific action.

Peptide hormones vs. proteins

Both peptides and proteins are fundamentally made up of strings of amino acids linked by peptide bonds. The primary distinction between them lies in their size. Generally, a chain of fewer than 100 amino acids is referred to as a peptide, while longer chains, often with more complex folding and three-dimensional structures, are classified as proteins.

While some proteins can also act as hormones (protein hormones), many proteins have other diverse roles within the body, such as providing structural support (like collagen), acting as enzymes to catalyze biochemical reactions, or transporting molecules.

If peptide hormones are direct signalling molecules, proteins carry out the tasks within the cell and the body.

Also read: Understanding the Connection Between Gut Health and Hormones

Peptide hormones vs. other hormones

While peptide hormones are key communicators, they are not the only type of hormone in your body. Other major classes include lipid-derived and amino acid-derived hormones. Here's a brief look at how they differ:

Lipid-derived hormones (steroid hormones): These hormones, such as oestrogen, testosterone, and cortisol, are derived from cholesterol (a type of lipid or fat). Being fat-soluble, they can easily pass through the cell membranes of their target cells and typically bind to receptors located inside the cell, often influencing gene expression directly.
Amino acid-derived hormones: This group includes hormones like thyroid hormones (T3 and T4) and catecholamines (such as adrenaline and noradrenaline). They often consist of single amino acids and carry different structural and functional characteristics. For instance, thyroid hormones bind to intracellular receptors, while catecholamines bind to receptors on the cell surface.

As you've got a general overview, it's time to get into the nitty-gritty of how these peptide hormones actually do their job!

How do peptide hormones work?

The journey of a peptide hormone begins with its release from endocrine cells into the bloodstream. Specific physiological signals, such as changes in blood glucose levels or signals from the nervous system, often trigger this release. Once in circulation, these water-soluble hormones travel throughout the body, seeking out their target cells.

Peptide hormones exert their effects through a specific interaction with their target cells:

Binding to surface receptors: Due to their water-soluble nature, peptide hormones can't easily slip through the cell's fatty outer layer (the cell membrane). Instead, they bind to special docking stations on the cell surface called receptors.
Triggering a response: This binding initiates a crucial step, activating a sequence of events within the cell known as intracellular signaling pathways. These pathways involve the activation of various molecules inside the cell.
Leading to the cellular action: Ultimately, this internal signalling leads to a specific physiological response within the target cell. This could be anything from telling the cell to take in sugar (like insulin does) to releasing another hormone. The specific receptor ensures that only the correct peptide hormone triggers a response in that particular cell.

Interaction with other hormones

Peptide hormones often collaborate with other types of hormones and the nervous system to maintain homeostasis.

For instance, insulin, a peptide hormone, works alongside cortisol, a steroid hormone, to regulate blood sugar. While insulin promotes glucose uptake and storage when blood sugar is high, cortisol can increase glucose availability during stress. Each acts under different conditions but in a complementary manner.

Can stress lead to weight gain? Watch the video below to find out how stress can make you fat and discover some simple tips to avoid it.

Now, let's explore the amazing functions these little powerhouses perform to keep us ticking!

Functions of peptide hormones

Peptide hormones manage everything from keeping you energised after a meal to helping you recover from a stressful situation. Their precise actions throughout your body are fundamental to maintaining overall health and well-being.

Here are some of the crucial roles that peptide hormones play:

Regulation of metabolism and energy balance: Peptide hormones trigger insulin release after eating, allowing glucose to be used for energy. When blood sugar drops, other peptide hormones release stored glucose, ensuring constant energy for the body and brain.
Control of growth and development: Certain peptide hormones stimulate growth factor production, promoting cell growth and differentiation, especially during childhood and adolescence. They also aid tissue repair and regeneration throughout life.
Management of appetite and satiety: Gut peptide hormones signal fullness to the brain after meals, regulating appetite and preventing overeating. Conversely, hormones from an empty stomach signal hunger, managing energy intake and body weight.
Modulation of mood and behaviour: Specific peptide hormones in your brain trigger the release of neurotransmitters that influence emotions. Some promote feelings of pleasure and reduce the perception of pain, while others foster social bonds and trust.
Regulation of reproductive functions: Peptide hormones play critical roles in the development and function of the reproductive system. They regulate the production of sex cells (sperm and eggs) and control the cyclical hormonal changes that govern the menstrual cycle and pregnancy.
Maintenance of fluid and electrolyte balance: These hormones act on your kidneys to control the reabsorption of water and electrolytes, ensuring that your body maintains the proper balance of fluids and essential minerals necessary for cell function and overall health.
Stress Response: When you encounter stress, peptide hormones are released that initiate a cascade of hormonal changes. These changes help your body mobilize energy reserves and prepare to cope with the stressful situation.

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Next, let’s meet some of these hormonal MVPs in action!

Examples of peptide hormones in the body

Peptide hormones are fascinating regulators of numerous physiological processes in the body. Let's explore some well-known peptide hormones and their primary functions:

Insulin: This hormone facilitates the uptake of glucose from the bloodstream into cells.
Adrenocorticotropic hormone (ACTH): It stimulates the adrenal glands to release cortisol, a stress hormone.
Oxytocin: Often called the ‘love hormone,’ oxytocin is involved in social bonding, trust, and childbirth.
Endorphins: These are natural pain relievers and mood elevators, released in response to exercise or pleasure.
Growth hormone: This peptide hormone supports growth, cell reproduction, and regeneration.
Antidiuretic hormone (ADH): It is involved in regulating water reabsorption in the kidneys.
Follicle-stimulating hormone (FSH): It stimulates the development of eggs in ovaries and sperm in testes.
Luteinizing hormone (LH): It triggers ovulation in women and testosterone production in men.
Ghrelin: Known as the ‘hunger hormone,’ ghrelin stimulates appetite.
Leptin: This satiety hormone signals fullness to the brain.
Cholecystokinin (CCK): Released in the gut, this hormone promotes satiety and aids digestion.

Peptide hormones, though tiny in structure, are truly mighty in their impact. They act as essential communication molecules, diligently working to maintain the delicate balance within your body and ensuring the proper functioning of countless systems, from managing your energy levels and mood to regulating growth and reproduction.

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