What Are Peptide Hormones?


Written by Elite HRT on April 08, 2021

Medically reviewed by

Camille Freking, Regulatory Affairs Specialist, MEDICAL ADVISOR

Hormones are chemical messengers in the body that tell the body to carry out different activities from making you pee more to growing more muscle. There are different types of hormones including peptide hormones, protein hormones, and lipid hormones.

 Peptide hormones are just a little different than the others but are very important in maintaining the body’s optimal functioning. Some of the peptide hormones include oxytocin, growth hormone, insulin, follicle-stimulating hormone, thyroid-stimulating hormone, calcitonin, prolactin, glucagon, vasopressin, and adrenocorticotropic hormone. 

Keep reading to learn what peptide hormones are, how they work in the body, and some of the most notable peptide hormones in the body, especially in terms of how they bind to the cell surface to carry out a specific task.

Peptide Hormones

Peptide hormones are those that are made of peptides. A peptide is a chain of amino acids. Amino acids are the building blocks of proteins. So, peptide hormones are a hormone built up of a short or long chain of amino acids. 

Peptide hormones are the largest type of hormone out of them all. Peptide hormones are able to be dissolved in water which is called water-soluble or hydrophilic. This is important when it comes to how they work in the body. 

How Peptide Hormones Work in the Body

As mentioned before peptide hormones are water-soluble. So, when a peptide hormone leaves its gland it is able to travel through the blood freely and unbound to anything else — meaning that it simply floats through the blood until it meets its target organ or cell.  

Once the peptide hormone reaches its destination it attaches to a receptor on the outside of a cell membrane.  Since the cell’s plasma membrane is made of lipids or fats the peptide hormone is not able to make it through the membrane and into the cell. This is why the receptor for the peptide hormone has to be on the outside of the cell. 

From there, there are a number of changes that occur so that the signal can be transmitted into the cell and the appropriate action can be taken. 


Oxytocin is one of the most well-known hormones that there is, and it happens to be a peptide hormone. Oxytocin is made by the posterior pituitary gland in the brain. When you think of oxytocin, think about the love hormone. Oxytocin is released when people hug, and really anytime you have a loving or intimate interaction with someone, especially physical. 

It is also well-known for its role in childbirth. In childbirth, oxytocin is released to stimulate contractions of the uterus to help birth the baby. It also signals to the breasts to release breast milk, also known as “let down.” 

Growth Hormone

Growth hormone (GH) is another peptide hormone that mainly focuses on physical growth and development. This is an important hormone for both children and adults, but the most drastic changes are seen in children because they have most of their growth during that time period. 

However, in both adults and children growth hormone is helpful for boosting muscle growth, decreasing fat content in the body, boosting metabolism, and can increase height in children. Growth hormone can be used therapeutically for those with low levels of GH, such as in conditions like growth hormone deficiency. 

Growth hormone should not be used for those that are trying to simply boost athletic performance and should be used only under the guidance of a licensed medical professional.


You may associate insulin with diabetes mellitus because diabetes involves a lack of the insulin hormone. 

The insulin hormone is released by the pancreas. Insulin’s role is to assist sugars into the cells so that they can use them for energy. The sugars come from the foods you eat. If your body does not have enough insulin, like in diabetes, the sugar stays in the blood and does not make it into the cells. When this occurs, your body does not get the energy it needs and you have high blood sugar. This can leave you feeling hot, sweaty, thirsty, and a fast heartbeat. 

Insulin is very important to keep your body working properly by getting the energy it needs to survive. 


Glucagon is almost the opposite to insulin. While insulin brings blood sugar into the cell, glucagon takes the sugar out of the cell. You may be wondering why you would want to take sugar out of the cell if that’s what gives you energy — well, glucagon moves sugar that’s essentially in storage versus sugar that’s in the cell to be used. 

If your body recognizes that your blood sugar is too low it will signal for glucagon to be released and will tell the body to release sugar from the cells and into the blood to fix the problem. If you have low blood sugar you may experience symptoms such as feeling cold, clammy, dizzy, and feeling shaky. 

Glucagon is very important to maintaining an appropriate balance of blood sugar so that your body gets the energy it needs while having enough sugar in the blood. 

Thyroid Stimulating Hormone

The thyroid is responsible for creating T3 and T4 hormones which are important for maintaining your body’s metabolism. Keeping those hormones in balance is important because they can impact everything from the speed that your heart beats to how much weight you gain or lose.  

To keep the thyroid hormones in balance thyroid-stimulating hormone is an important part of the cycle. Thyroid-stimulating hormone is released from the anterior pituitary gland and signals to the thyroid to release T3 and T4 hormones if necessary. 

If the body recognizes that there is too much T3 and T4 being produced it will reduce the amount of thyroid-stimulating hormone that is released from the pituitary gland. 


Do you ever imagine what people would be like if we didn’t have bones? Well, you would probably be like a pile of skin and muscles, you wouldn’t be able to walk, and you could barely move. 

Bones sometimes don’t get the credit that they deserve. Well, calcitonin is one of the hormones that help to keep bones in the best shape and balance the levels of calcium in the blood. 

Calcium is an element that is very important for the body but needs to be kept in a certain range so that there aren’t any negative effects. If there is too much calcium in the blood you could have changes in your heart rhythm, confusion, weak bones, and more. 

So, if the body recognizes that there is too much calcium in the blood it will release calcitonin so that calcium can move from the blood and into the bones. Having more calcium in the bones makes the bones stronger and also keeps the calcium balance intact. 


Prolactin is a hormone that is most important for creating breast milk. Prolactin is made in the anterior pituitary gland. Prolactin levels begin to rise during pregnancy and after childbirth. 

When prolactin levels rise women will begin to create breast milk to feed their baby. Having the right amount of prolactin is important for having an adequate milk supply and to keep your other body systems in balance. 

You may be surprised to know that prolactin is also made in males, however, we do not know the exact purpose of this hormone in the male body. 


Vasopressin is another hormone that does not get the attention it deserves. Vasopressin is also known as antidiuretic hormone, or ADH, and is released from the posterior pituitary gland. When vasopressin is released the kidneys are told to hold on to excess water and reduce the amount that you urinate.  

Holding onto water can be a compensatory mechanism if you are in a situation where you need more fluids such as if you are dehydrated or if you have low blood pressure. 

Vasopressin can be used as a medication in certain situations such as if you have lost a lot of blood, to prevent or treat stomach conditions after surgery, or in cases of diabetes insipidus.


Peptide hormones are so much more than a simple chain of amino acids. They affect almost every system in the body and help to balance the body carefully so that I can work as well as possible. 

Keep in mind that these are only some of the many peptide hormones and that others play important roles in the body as well. Because people do not always have the right amount of hormone in their body there are medical uses for these hormones called hormone replacement therapy.  

Using insulin for diabetes is just one example of using a peptide hormone in a therapeutic setting.  Another example is using growth hormone for someone with a growth hormone deficiency that is unable to grow to the proper size. 

If you’re looking to get more information about hormone replacement therapy today, get in touch with the experts now at Elite HRT


18.1 Types of Hormones | Concepts of Biology 

Hypercalcemia – Symptoms and causes | Mayo Clinic

Vasopressin | University of Michigan Health