Types of hormones and their functions in the human body

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

Hormones are molecules of different nature that are produced in the secretory or endocrine glands.. Working together with the nervous system, they are responsible for the way we act, feel and think.

The different types of hormones are released into the Blood vessels or interstitial space where they circulate on their own (bioavailable), or are associated with certain proteins until they reach the 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 or a vertebrate animal, it is responsible for regulating several important functions. But... why are hormones so important?

One of the functions they perform is that they ensure proper growth. In humans, the pituitary gland is responsible for secreting growth hormones during childhood and adolescence. In invertebrate animals, such as insects, growth hormone is involved in molting or the renewal of the integuments (body coverings), i.e. 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
• Proper development
• Reproduction
• Sexual characteristics
• Energy use and storage
• Blood levels of fluids, salt, and sugar

Coordinating with the brain

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

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

Classification of hormones: what types of hormones are there?

However, there are different classifications of hormones, there are different classifications of hormones.

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

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

Depending on whether they have their effect on the same cells that synthesized them or on contiguous cells, hormones can be:

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

2. According to their chemical composition

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

• Peptide HormonesThese hormones are composed of amino acid chains, polypeptides or oligopeptides. The great majority of this type of hormones do not manage to cross the plasma membrane of the target cells, which means that the receptors of this type of hormones are located on the cell surface. Among the peptide hormones, we find: insulin, growth hormones or vasopressin.
• Amino acid derivativesThese hormones are derived from different amino acids, such as tryptophan or tyrosine. For example, adrenaline.
• Lipid hormonesThis type of hormones are eicosanoids or steroids. Unlike the previous ones, they are able to cross the plasma membranes. Prostaglandins, cortisol and testosterone are some examples.

3. According to their nature

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

• Steroid HormonesThese hormones come from cholesterol and are produced mainly in the ovaries and testes, as well as in the placenta and adrenal cortex. Some examples are: androgens and testosterone, produced in the testes; and progesterone and estrogen, which are produced in the ovaries.
• Protein HormonesThese are hormones made up of chains of amino acids and peptides.
• Phenolic DerivativesAlthough they are proteinaceous in nature, they have a low molecular weight. An example is adrenaline, which intervenes in situations in which a large part of the body's energy reserves must be invested in moving the muscles quickly.

4. According to their solubility in the aqueous medium

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

• Hydrophilic (water-soluble) hormones.These hormones are soluble in the aqueous medium. Since the target tissue has a membrane with lipid characteristics, hydrophilic hormones cannot cross the membrane. Therefore, these types of hormones bind to receptors on the outside of the target tissue. For example: insulin, adrenaline or glucagon.
• Lipophilic (lipophilic) hormonesThese hormones are not soluble in water, but are soluble in lipids. Unlike the previous ones, they can cross the membrane. Therefore, the receptors of these 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 taking place within the organism 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 performing different functions. In addition, these substances vary according to the type of gland that secretes them and their location.

The main endocrine glands are:

• The pituitary gland or hypophysisIt 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 gland, secreting chemicals that can stimulate or inhibit pituitary hormone secretions.
• The thymusSecretes a hormone called thymosin, which stimulates the growth of immune cells.
• The pineal glandThe pineal gland produces melatonin, a hormone that plays an important role in adjusting sleep and wake cycles.
• The testiclesThese produce hormones called estrogens, the most important of which is testosterone, which signals to males that it is time to begin the body changes associated with puberty, such as a change in voice and the growth of beards and pubic hair.
• The ovariesThe ovaries secrete estrogen and progesterone. Estrogen tells girls when to begin the body changes associated with puberty.
• The thyroidThyroxine and triiodothyronine, hormones that control the rate at which cells burn fuel from food to produce energy, are produced in this endocrine gland.
• The adrenal glandsThe adrenal glands: These glands have two parts. One produces hormones called corticosteroids, which are involved in mineral and water balance, stress response, metabolism, the immune system, and sexual development and function. The other part produces catecholamines, e.g. adrenaline.
• The parathyroid glandFrom here parathyroid, a hormone related to blood calcium concentration, is released.
• The pancreasThe pancreas: Secretes insulin and glucagon, which allows it to maintain a stable blood glucose concentration 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 behaviour: a psychological approach. Cambridge: Cambridge Univ. Press.
• Redaktor., Molina, Patricia E. (2018). Endocrine physiology. McGraw-Hill Education.