Types Of Hormones And Their Functions In The Human Body

We discover hormones and their multiple functions in our brain and body.

Hormones are molecules of diverse nature that are produced in the secretory or endocrine glands. Working together with the nervous system, they are responsible for us acting, feeling and thinking as we do.

The different types of hormones are released in the blood vessels or in the interstitial space where they circulate alone (bioavailable), or are associated with certain proteins until they reach the target (or target) organs or tissues where they act. Hormones are part of the group of chemical messengers, which also includes neurotransmitters such as dopamine, serotonin or GABA.

The most important functions of hormones

The functions of hormones are varied, but whether a hormone comes from a plant, an invertebrate animal, or a vertebrate animal, it regulates several important functions. Now …  why are hormones so important?

One of the functions they perform is that they ensure correct growth. In humans, the  pituitary gland is responsible for secreting growth hormones during childhood and adolescence. In invertebrate animals, such as insects, growth hormone intervenes in the shedding or renewal of the integuments (body coatings), that is, the shedding of the outer layer. In the case of plants, several hormones are responsible for the proper growth of roots, leaves, and flowers.

In addition to this all-important function, the functions of hormones include :

  • Dynamic action on various organs
  • Activate or inhibit enzymes
  • Appropriate development
  • Reproduction
  • Sexual characteristics
  • Energy use and storage
  • Blood levels of fluid, salt, and sugar

Coordinating with the brain

Another fact that we must bear in mind is that some biological processes are less expensive if, instead of creating a constant torrent of electrical firing by neurons to activate certain regions of the body, we simply emit types of hormones and let them be carried away through the blood until it reaches its destination. In this way we achieve an effect that lasts for several minutes while our nervous system can take care of other things.

In this sense, hormones work in coordination with the brain to activate and deactivate parts of the body and thus ensure that we adapt to circumstances in real time. Of course, the effects of the release of these hormones take a little longer to be noticed than those caused by neurons.

Classification of hormones: what types of hormones are there

Now, there are different classifications of hormones.  

What are these classifications and according to what criteria are they established? We will explain it to you below.

1. By proximity of your synthesis site to your site of action

Depending on whether they act on the same cells that synthesized it or on neighboring cells, the hormones can be:

  • Autocrine Hormones : Autocrine hormones act on the same cells that synthesized them.
  • Paracrine Hormones : They are those hormones that act close to where they were synthesized, that is, the effect of the hormone occurs in a neighboring cell to the emitting cell.

2. According to its chemical composition

According to their chemical composition, there are four types of hormones

  • Peptide Hormones : These hormones are made up of chains of amino acids, polypeptides, or oligopeptides. The vast majority of these types of hormones fail to penetrate the plasma membrane of the target cells, this causes the receptors of this class of hormones to be located on the cell surface. Among the peptide hormones, we find: insulin, growth hormones or vasopressin.
  • Derivatives of Amino Acids : These hormones emanate from different amino acids, such as tryptophan or tyrosine. For example, adrenaline.
  • Lipid Hormones : These types of hormones are eicosanoids or steroids. Unlike the previous ones if they manage to cross the plasma membranes. Prostaglandins, cortisol, and testosterone are some examples.

3. According to its nature

Depending on this class of substances produced by the body through its nature, there are the following types of hormones:

  • Steroid Hormones : These hormones come from cholesterol and are produced mainly in the ovaries and testes, as well as in the placenta and the adrenal cortex. Some examples are: androgens and testosterone, produced in the testicles; and progesterone and estrogen, which are made in the ovaries.
  • Protein Hormones : They are hormones made up of chains of amino acids and peptides.
  • Phenolic Derivatives : Despite being protein in nature, they have a low molecular weight. An example is adrenaline, which intervenes in situations where a large part of the body’s energy reserves must be invested in moving muscles rapidly.

4. According to its solubility in the aqueous medium

There are two types of hormones according to their solubility in the aqueous medium:

  • Hydrophilic Hormones (water soluble) : These hormones are soluble in the aqueous medium. Since the target tissue has a membrane with lipid characteristics, hydrophilic hormones cannot cross the membrane. Thus, these types of hormones bind to receptors that are outside the target tissue. For example: insulin, adrenaline or glucagon.
  • Lipophilic (lipophilic) hormones: These hormones are not soluble in water, but they are soluble in lipids. Unlike the previous ones, these can cross the membrane. Therefore, the receptors of this type of hormones can bind to intracellular receptors to carry out their action. Examples: thyroid hormone or steroid hormones.

Types of endocrine glands

Hormones are produced in endocrine glands throughout the body. In many ways, our nervous system needs the collaboration of other parts of the body to ensure that the processes that take place within the body are coordinated and a certain balance is maintained. 

To achieve this level of coordination, our brain regulates the release of various types of hormones responsible for carrying out different functions. In addition, this class of substances vary according to the type of gland that secretes them, and its location.

The main endocrine glands are:

  • The  pituitary or pituitary gland : It is considered the most important gland of the endocrine system, because it produces hormones that regulate the functioning of other endocrine glands. It can be influenced by factors such as emotions and seasonal changes.
  • The hypothalamus : This endocrine gland controls the functioning of the pituitary, secreting chemicals that can stimulate or inhibit hormonal secretions from the pituitary.
  • The thymus : It secretes a hormone called thymosin, responsible for stimulating the growth of immune cells
  • The pineal gland : Produces melatonin, a hormone that plays an important role in adjusting the sleep and wake cycles.
  • The testicles : These produce hormones called estrogens, the most important of which is testosterone, which indicates to males that the time has come to start the body changes associated with puberty, for example, the change of voice and the growth of the beard. and pubic hair.
  • The ovaries : They secrete estrogen and progesterone. Estrogen signals to girls when to initiate the bodily changes associated with puberty.
  • The thyroid : This endocrine gland produces thyroxine and triiodothyronine, hormones that control the rate at which cells burn fuel from food to produce energy.
  • The adrenal glands : These glands have two parts. One produces hormones called corticosteroids, which are related to the balance between mineral salts and water, the response to stress, metabolism, the immune system, and sexual development and function. The other part produces catecholamines, for example adrenaline
  • The  parathyroid : From here parathyroid is released, a hormone related to the concentration of calcium in the blood.
  • The pancreas : Secretes insulin and glucagon, which allows to maintain a stable concentration of glucose in the blood and to supply the body with enough fuel to produce the energy it needs.

Bibliographic references:

  • Kosfeld M et al. (2005). Oxytocin increases trust in humans. Nature 435: 673-676. 
  • Marieb, Elaine. (2014). Anatomy & physiology. Glenview, IL: Pearson Education, Inc.
  • Neave N. (2008). Hormones and behavior: a psychological approach. Cambridge: Cambridge Univ. Press.  
  • Redaktor., Molina, Patricia E. (2018). Endocrine physiology. McGraw-Hill Education.  

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