Hormones


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Hormones can simply be defined as organic chemical substances that are produced by cells, glands or body organs that are responsible for maintaining the body's homeostasis and regulation of various activities of the body. Hormones are interconnected and therefore the functioning of one affects a chain of others. They are usually released in large volumes to trigger responses from body tissues and organs. They therefore act as messengers that carry different signals from cells in one party of the body to another.

Upon their release from their respective glands, hormones move to intended organs within the blood stream, triggering a response from the cells. Direct secretion of hormones into the blood stream is referred to as endocrine secretion. They possess the following characteristics:

  • They are basically chemical messengers.
  • They are chemical signals found in body fluids, especially the blood.
  • They alter the behaviors of cells.
  • They don't catalyze reactions, enzymes do.
  • They're only produced when necessary.
  • The feedback effect of the nervous system regulates their secretion.
  • They're responsible for the stimulation or inhibition of specific organs.

Classification of Hormones

There are three main ways hormones are classified:

1. Traditional Classification

Here, hormones are classified based on how they are secreted, transported, and acted upon. They fall under three different categories:

a) Neurohormones: This group of hormones are produced by the neuroendocrine cells and discharged at the terminals of the nerve endings. They are diffused into the blood stream during transportation into various parts of the body.

b) Local Hormones: This group is usually discharged into the interstitial fluid and acts on nearby cells (paracrine hormones) while others act on the very cells through which they were secreted (autocrine hormones).

c) Classical Hormones: They come from the endocrine cells and are secreted into the interstitial fluid before diffusing into the bloodstream and transported to all parts of the body.

2. Structural Classification

There are four main groups of hormones, classified based on their structures. They are:

a) Steroid Hormones: These hormones are derivatives of cholesterol and dissolve in lipids. They include those released by the adrenal glands, such as mineral corticosteroids and glucocorticosteroids, and sex hormones like progesterone, estrogens, and androgens. This group of hormones is crucial to the body as they are involved in critical functions like stress response, sexual development and balance of water.

b) Hormones Derived from Amino Acids: They include tryptophan and tyrosine (e.g catecholamines and the thyroid hormone). The thyroid hormone is especially important due to its role of regulating the growth and development of various body organs and metabolism.

Tryptophan amino acid is crucial in the secretion of melatonin and serotonin which regulates mood and intestinal movements. Epinephrine and norepoinephrine are catecholamines that are basically neurotransmitters and stress management.

c) Peptide Hormones: They are derivatives of peptides, and their precursors are the prohormones produced by the endoplasmic reticulum. This group of hormones is usually kept in the vesicle of the cells awaiting requisite stimuli for their discharge into the blood stream and absorption. They include thyroid stimulating hormone (TSH), prolactin vasopressin and insulin.

d) Hormones Derived from Fatty Acids: They are generally known as eicosanoids and synthesized from arachidonic acid which is found in every body cell. They are responsible for blood clotting, blood pressure, and regulation of inflammation.

3. Classification Based on Mode of Action

Here, there are two main types of hormones:

a) Short Acting: These hormones are known to trigger a response that can be said to be delayed. They include the steroid hormones of the adrenal cortex and reproductive organs.

b) Quick Acting: These hormones are trigger urgent response from cells. They include amine and protein hormones.

Different Functions of Hormones

The function of the hormones depends on their purpose. They can inhibit or stimulate growth, they can control your mood swings, regulate metabolism, control hunger, and overall functioning of various body systems, among others. Testosterone, for example, is responsive the masculine characteristics such as deep voice and beards in men while for feminine characteristics is the estradiol and progesterone. It is therefore important to note that every hormone produced by the body has a specific function.

How Are Hormones Regulated?

The regulation of hormones is realized through two main mechanisms: the positive and negative feedback mechanisms. The body also has counter regulatory hormones.

Negative Feedback Mechanisms: Here, cells responsible for the production of the hormones cease their production the moment a certain effect is detected. A typical example of this mechanism is the insulin production. When you consume glucose, its level in the blood increases. The ?-cells found in the pancreas respond by releasing insulin which increases glucose update in the intended cells. As the update of available glucose by various cells increases, its levels decrease and maintain balance, production of insulin is halted by the ?-cells, restoring balance.

Positive Feedback Mechanism: This is the opposite of the negative feedback mechanism. Here, the hormone effects trigger the secretion of more hormones. An example of such hormones include the oxytocin produced by the pituitary glands that are responsible for the contractions of the uterus and the cervix during childbirth. The glands keep producing the hormone until the time the child is successfully born.

Counter Regulatory Hormones: There are some body activities that require more than one hormone. A good example is how glucose levels are controlled in the blood. When the glucose levels drop, hormones that inhibit glucose reuptake are released to counter the effect of insulin. In this case, glucagon and epinephrine. They generally work the opposite of each other.

Hormone Therapy

Hormone therapy is basically the use of specialized drugs to correct disorders resulting from hormonal imbalance. These drugs are formulated based on a clear understanding of the functioning of body organs and hormones. Decadron, for example, is a corticosteroid medication used in the treatment of conditions, such as skin diseases, asthma, rheumatic complications, and chronic obstructive disorders, among others. Other similar drugs include Medrol, Deltasone, and Synthroid. Some of these drugs are prescription-only and are associated with a number of side effects. It is therefore important to always consult your doctor for a proper guidance.