What Are Protein Hormones?

Elite HRT

Written by Elite HRT on April 10, 2021

Medically reviewed by

Camille Freking, Regulatory Affairs Specialist, MEDICAL ADVISOR

At some point or another, you have most likely heard of hormones. Hormones like testosterone and estrogen are frequently discussed as they relate to sex differences and their associated traits. 

Both of these hormones are steroid hormones, which means that they consist of four interconnected carbon rings. While steroid hormones are important for ideal bodily function, they only represent a small portion of the hormones in the body. The other hormone types include peptide, protein, and amine hormones. Each has a unique differentiating composition which allows it to interact with (i.e., bind) in a specific manner with its target cell.

Below is an in-depth look at protein and peptide hormones as well as how you can utilize them in hormone replacement therapy

Being educated on what protein hormones are, how they work, and how they impact the body can allow you to be more informed in your health which can allow you to take charge of it. 

Non-Steroid Hormones

Hormone classifications are great for quickly being able to identify what a hormone is and its mode of action is, however they can be somewhat vague. These blurry lines between classification are mostly seen in the differences between amine, peptide, and protein hormones. 

Non-steroidal hormones all have a link to proteins. The best way to understand these differences is to look at the specifics surrounding proteins.

Amino acids are the most basic unit of proteins. In the human body, there are 20 different amino acids that can be arranged in a seemingly limitless number of combinations. Amine hormones are hormones that have a single amino acid group attached to them.

Peptide chains are short chains of two or more amino acids. The added complexity of additional amino acids can allow for a more specific molecule and function. There are many different peptides as there are so many different arrangements of amino acids possible. Peptide hormones are hormones that have a peptide chain attached to them.

Proteins are long chains of amino acids and consist of many peptide chains linked together. Proteins are much larger in size and rather than being a straight chain, they typically fold in a specific way to form a protein. 

For the sake of discussion peptides, proteins, and amine hormones are lumped together as protein hormones because of their similarity in interaction and structure. 

How Protein Associated Hormones Work in the Body

While hormones are lumped into a broad category, the different hormone types have different mechanisms of action. For steroid hormones, the molecule is able to pass through the cell membrane and directly signal changes within a cell. Non-steroid hormones like protein hormones, act as an indirect signaling molecule because of their diminished ability to pass through the cellular membrane.

Protein hormones have many different points of interaction due to the long chain of amino acids with unique chemical compositions. This unique sequence of amino acid interactions and the shape of the protein act as a key that is highly specified. As protein hormones circulate throughout the body they are able to signal changes in specific cells that have the corresponding lock on the surface known as receptors.

Receptors are molecules that extend through the membrane of cells and allow for the cell to react to changes occurring outside of it. Depending on the cell type and where it is located dictates what receptors it will have and in what relative amount. 

When a protein hormone finds a compatible sequence on the surface receptors, it causes a chemical signaling cascade within the cell which can cause actions like the transcription to increase or decrease. 

Examples of Protein Associated Hormones

Protein hormones have a wide range of functions within the human body. Even though protein hormones only interact with the membranes of cells, they are crucial in the proper functioning of the human body. Below is a look at five different protein hormones that are critical to have in the human body. 

Growth Hormone

Human growth hormone is one of the very few molecules within the human body that is self-explanatory in what it does within the body. Growth hormone, as you probably guessed, facilitates tissue growth within the body. 

Growth hormone secretion is tightly regulated by the pituitary gland in the brain and is a critical hormone in the growth and development of humans. Growth hormone interacts with the surface of many different cells which alters the growth rate and metabolism within the body. 

At its most basic, growth hormone interacts with cells like adipocytes to increase energy availability while simultaneously signaling other cells to utilize this energy to grow. 


Epinephrine may sound unfamiliar, but it is more commonly known as adrenaline. Adrenaline is a hormone produced by the adrenal glands which are located on top of the kidneys. The hormone is a major player in the human stress response and fight or flight. 

When the brain identifies a stressful or dangerous event it signals the adrenal glands to secrete adrenaline into the bloodstream. The molecule quickly attaches to designated receptors on cell membranes which initiates body-wide changes. These changes include increased heart rate, elevated blood pressure, increased respiration rate, and decreased rate of digestion. All of these changes prepare your body to act in the event of stress.

The effects of adrenaline can be both enjoyable and a nuisance. Adrenaline junkies for instance chase the rush experienced by the secretion of adrenaline by doing seemingly extreme and exciting things. On the flip side, those that experience chronic stress experience the negative aspect of constant body stimulation through adrenaline. 


Melatonin is a hormone that is secreted by the pineal gland. Melatonin interacts with your body to aid in going to sleep and staying asleep. The regulation of melatonin varies from person to person. The main reason melatonin varies from person to person is environmental factors.

One of the largest environmental factors that can alter melatonin levels is light. Humans over evolutionary history have traditionally been diurnal, which means that people were active during the day and inactive at night. The light from the sun was a key indication to wake up while the dimming of light in the evening signaled the body to prepare for sleep. 

Melatonin is a hormone that has a significant influence on people’s sleep and because of this, many people who struggle with their sleep may choose to supplement it to help support their sleep. 


Insulin is a crucial peptide hormone that is a necessary component of carbohydrate metabolism and blood sugar regulation. Insulin is secreted by the pancreas and is signaled by an elevation in blood sugar.

When your body digests carbohydrates it breaks them down into their most basic molecules where it is then absorbed in the digestive tract into the bloodstream. When blood sugar levels increase it causes the pancreas to secrete insulin. Insulin attaches to the cell membrane of cells throughout the body and allows cells to take in the sugar in the blood for energy. 

Without insulin, blood sugar levels can get too high and can result in health complications. People with diabetes have a dysfunction in the insulin signaling pathway and need to take supplemental insulin to survive. 


Glucagon is another peptide hormone that is released by the pancreas. Glucagon plays another important role in the maintenance of blood sugar levels. When you are between meals or sleeping your body is not getting carbohydrates from the digestive system. During this time your body looks to energy reserves that it has built over time. 

Glycogen is a form of reserve energy that the body builds over time when there is extra carbohydrate availability when you eat. The glucagon hormone is what signals the body to start the breakdown of glycogen into glucose to maintain a healthy blood sugar level. 

Hormone Therapy

Hormone therapy is the therapeutic utilization of supplemental hormones to help with a deficiency in hormone production. When people think of hormone replacement they most typically think of estrogen and testosterone. While these can often be the targets of hormone replacement therapy, hormone therapy extends well beyond steroid hormones. 

Protein hormones are just as important as steroid hormones. When deficiencies in protein hormones occur it can be detrimental to your health and wellbeing. 

Elite HRT has you covered for both your steroidal and protein-based hormone needs. 


Hormonal regulation within the human body is tightly regulated and runs like a well-oiled machine. Both protein and lipid-based hormones provide a chemical means of signaling the body to undergo physiological changes. 

Supporting your hormonal health is one of the best ways you can facilitate great wellbeing and Elite HRT is here to help every step of the way. 


Melatonin and Sleep | Sleep Foundation

17.2 Hormones – Anatomy & Physiology | Oregon State University

Growth Hormone (Somatotropin) Colorado State University