The endocrine system is complex and has many ways to categorize hormones and glands. These categories can help us to have a better understanding of exactly how a hormone or gland works.
Hormones can be classified according to the body system they impact, the effect it has, which gland it comes from, the structure of the hormone, and how the hormone works.
A tropic hormone is just one of many ways to classify hormones, but it is a very important subgroup to understand.
Keep reading to learn what hormones are, what the actions of hormones are, which type of hormone a tropic hormone is, and examples of tropic hormones.
What Are Hormones?
Have you ever wondered how your body can go from seeing it is dark out to know it is time for sleep? Or how when you don’t drink a lot of water your body knows to not go to the bathroom as much?
Behind all of these little behaviors and actions, the body is observing stimuli in the body and sending itself messages. The messengers that carry the instructions on what to do are the hormones.
Hormones are chemical messengers that are sent all throughout the body to carry out many functions. Often, one hormone can have impacts on multiple systems of the body.
For example, you may think of testosterone and only think of the male reproductive system. However, it also impacts your mood, musculoskeletal system, and hair growth.
Hormones are small but mighty and are responsible for a wealth of roles in the human body.
What Are the Actions of Hormones?
Not all hormones act the same. Some hormones are like managers and tell others what to do, while some are the workers and listen to the managers. This is the concept when it comes to tropic and trophic hormones.
Tropic hormones are the managers from the previous metaphor. Tropic hormones are those that signal to another gland to release a different hormone.
Tropic hormones are like the middlemen in the endocrine system because there is typically another hormone that signals to the tropic hormone to be released as well. They are crucial in the negative feedback loops to balance hormone levels. They can also be very helpful in diagnosing hormone issues based on the level of the tropic and trophic hormones.
The tropic hormones are generally released from the anterior lobe of the pituitary gland, also called “The Master Gland.”
Trophic hormones on the other hand are hormones that are released to complete an action at a tissue or just in the body. Trophic hormones are usually triggered by a tropic hormone to be released. Some trophic hormones simply respond to a change in the body.
Trophic hormones are released all over the body from various glands including the pituitary gland, adrenal glands, pancreas, testicles, and ovaries.
An example of a trophic hormone is prolactin. When prolactin is released the target organ is the mammary gland which then produces milk for the infant.
Trophic hormones are the final line of the endocrine system and send out the signals to get the work done.
What Type of Hormone Are Tropic Hormones?
As mentioned before, hormones can be differentiated by how they are made. Tropic hormones all happen to be peptide hormones, instead of lipid hormones or amine hormones.
A peptide hormone is one that is made from a chain of amino acids. The chain of amino acids is like instructions for which hormone it should be. Depending on which amino acids are chosen and which order they are in will make a different hormone. They are also shaped differently to give them different characteristics.
When it comes to peptide hormones they bind to receptors on the outside of the cell when it reaches the target gland. The sequence goes like this:
- The pituitary gland releases the tropic hormone.
- The hormone travels through the blood on its own. It does not need to attach to a protein in the blood because it is easily dissolved in water.
- It reaches the destination gland, called the target.
- The hormone binds to a specific receptor on the outside of the target cell. The receptor is on the outside because the hormone is water-soluble and cannot pass through the fat-soluble cell membrane.
- The target gland gets the message to release the trophic hormone.
- Once the trophic hormone is released, it will travel to the target organ where a function will be carried out.
Examples of Tropic Hormones
Follicle Stimulating Hormone
Follicle-stimulating hormone is a hormone that is released by the anterior pituitary gland is received at the ovary in women and testicles in men. In women, FSH acts as a tropic hormone by encouraging the release of the hormone estrogen. In addition to this tropic action, it also stimulates the growth of the egg or follicle to be ready for ovulation.
In men, the follicle-stimulating hormone is important because it stimulates sperm to be made. This allows the man to impregnate a woman and is fertile. Without adequate levels of FSH, the man may have infertility or difficulty conceiving a child with a partner.
Luteinizing hormone is close relative to follicle-stimulating hormone. It too is released from the anterior pituitary and received at the testes and ovaries. In women, it also is a tropic hormone by stimulating the release of estrogen from the follicle itself, instead of from the ovary. In addition, it also helps to release the follicle from the ovary and into the fallopian tube. Without LH the female would not be able to ovulate.
In males, the luteinizing hormone also plays a tropic hormone role. When LH is released the testicles receive the signal and stimulates the production of the hormone testosterone. Testosterone is important in sperm production, sex drive, and other non-reproductive functions.
Adrenocorticotropic hormone even has “tropic” in its name. It is a tropic hormone released from the anterior pituitary gland and has a target gland of the adrenal glands. The adrenal glands are the glands that sit on top of the kidneys and make a lot of vital hormones. The adrenal glands have an inside area called the medulla, and an outside portion called the cortex.
Adrenocorticotropic hormone addresses the cortex area of the adrenal glands, but only stimulates the production of glucocorticoids like cortisol. You may recognize cortisol as the stress hormone.
Cortisol is increased during times of stress and helps your body to respond appropriately. The adrenal glands also produce the hormones aldosterone, epinephrine, norepinephrine, and DHEA. However, adrenocorticotropic hormone only affects cortisol release.
Thyroid Stimulating Hormone
Thyroid disorders are some of the most common endocrine problems among children and adults. Because of this, it is so important to be aware of the thyroid, its hormone pathways, and the symptoms that could come along with thyroid dysfunction.
The tropic hormone related to the thyroid is the thyroid-stimulating hormone. This hormone is released from the anterior pituitary gland and signals to the thyroid gland to release T3 hormone (triiodothyronine) and T4 hormone (thyroxine). When T3 and T4 levels are down there is a signal to increase the production of thyroid-stimulating hormone to be released more.
The thyroid hormones themselves are in charge of balancing the body’s metabolism. The metabolism is how fast or slow the processes in the body occur. Some of the things that it controls are the bodyweight, speed of the heart, your body temperature, your skin texture, body hair growth, and more.
When the thyroid levels are not in balance there are usually some noticeable symptoms that significantly affect a person’s quality of life.
Corticotropin-releasing hormone is another tropic hormone, but this one is released by the hypothalamus. The hypothalamus is another gland in the brain, but it signals the pituitary gland to release hormones. The hypothalamus releases many hormones, including corticotropin-releasing hormone.
Corticotropin-releasing hormone signals to the anterior pituitary to release adrenocorticotropic hormone. So the axis is corticotropin-releasing hormone, adrenocorticotropic hormone, then cortisol.
It is funny to think that the words tropic hormones are not common to many people, but each one of us has so many of them in our bodies. Tropic hormones are a helpful middle step to telling other glands of the body to produce other hormones. It is a very smart system to have a cascade of hormone release instead of another mechanism. This helps to keep all of the hormones in balance with a negative feedback loop to prevent itself from creating too much or too little.
The body is able to recognize when it needs to adjust itself. When it can’t is when you have a hormone imbalance, and may need help from your doctor or Elite HRT with medications or hormone replacement therapy.
Tropic hormone | Endocrinology
Types of hormones | Khan Academy