Thyroid Hormones: Types And Functions In The Human Body
The endocrine system is made up of all those glands and hormones that act in our body. Hormones have a very important function in the regulation of basic physiological processes; In addition, they are also especially related to emotions.
In this article we will talk about thyroid hormones , a type of hormones synthesized by the thyroid gland and involved in metabolism. We will know its origin, its characteristics and its functions. In addition, we will analyze two important alterations that occur in the thyroid: hyperthyroidism and hypothyroidism.
Thyroid hormones are a type of hormones secreted in our body, and with important functions. Specifically, there are two: thyroxine (T4) and triiodothyronine (T3) These hormones are produced by the thyroid gland, a very important gland that regulates the body’s metabolism.
For its part, metabolism is involved in the processes that control the rate of activity of different cells and tissues, and encompasses a series of biological and chemical changes that occur continuously in the cells of our body.
thyroid hormones are based on tyrosine (one of the 20 amino acids that make up proteins). Specifically, thyroid hormones are amino hormones, along with other hormones: adrenaline, norepinephrine, melatonin and dopamine. Curiously, these last substances are in turn neurotransmitters (within the Central Nervous System (CNS)) and hormones (outside it).
But how do amino hormones act? What they do is bind to receptors on the cell membrane, starting a chain reaction in the cell. Let’s see the characteristics of the two thyroid hormones:
1. Thyroxine (T4)
Thyroxine was discovered and isolated in 1910 by Edward Calvin Kendall, an American researcher. Specifically, he isolated this substance from the thyroid of pigs.
At the level of functions, thyroxine what it mainly does is stimulate the body’s metabolism , in addition to participating in other processes. It is important, for proper functioning, that thyroxine levels are adequate and balanced, since levels that are too high or too low can cause alterations throughout the body.
This is what happens when thyroid disorders appear: hyperthyroidism (increase in thyroid hormones) and hypothyroidism (decrease in thyroid hormones), which we will explain in detail later.
2. Triiodothyronine (T3)
The second of the thyroid hormones, triiodothyronine, was discovered 42 years later than thyroxine, in 1952, by Jean Roche, a French biochemist.
This hormone It also plays a central role in the control and regulation of the body’s metabolism What it does is stimulate the metabolism of carbohydrates and fats, through the activation of oxygen consumption.
Furthermore, triiodothyronine also It is involved in different physiological processes in the body, such as growth, heart rate and body temperature (same as thyroxine). Finally, another function it performs is to degrade proteins within cells.
Where do thyroid hormones come from?
To understand where thyroid hormones come from, we must visualize a global diagram of the hormones and the endocrine system. The endocrine system is headed by the hypothalamus , the main secreter of hormones and the structure that “commands”, connecting the nervous system with the endocrine system. This, in turn, causes two types of hormones: releasing hormones, on the one hand, and oxytocin and vasopressin, on the other.
While the former (releasing hormones) act on the anterior hypothalamus (or adenohypophysis), the latter (oxytocin and vasopressin) act on the posterior hypothalamus (or neurohypophysis). The neurohypophysis is the “storage organ” of these hormones.
More specifically, the adenohypophysis produces trophic hormones, which in turn act on the glands; These produce the different hormones in the body. This is what happens with thyroid hormones: They are synthesized by the thyroid gland, which in turn receives signals from the anterior pituitary gland (a part of the hypothalamus, the anterior part).
That is, the thyroid hormones (thyroxine and triiodothyronine) come from the trophic hormones, which in turn come from the adenohypophysis. Specifically, thyroid hormones are stimulated by TSH and thyrotropin, a type of trophic hormones. In summary, what these structures (TSH and thyrotropin) actually do is stimulate the release of thyroid hormones in the thyroid gland.
Thyroid gland
The thyroid gland, or thyroid, is the structure that secretes thyroid hormones (actually, it is an organ). This endocrine gland, which is shaped like a butterfly, is located in the neck area just above the collarbone and below the apple.
It is not a very large structure, and weighs approximately 30 grams. The thyroid has an essential role in our body’s metabolism, as well as in other body functions such as body temperature. Besides, Its condition and functioning are closely related to our state of health
Some of the functions in which the thyroid gland is involved, through the action of its thyroid hormones, are the following:
Alterations
There are two important alterations in the thyroid gland which affect your thyroid hormone secretion: hyperthyroidism and hypothyroidism.
1. Hyperthyroidism
Hyperthyroidism consists of an elevated secretion of thyroid hormones; specifically, secretes too much thyroxine That is, the thyroid becomes overactive and as a consequence, the body’s metabolism accelerates.
This causes significant weight loss , as well as rapid and/or irregular heartbeats. It is related to symptoms of hyperarousal and mania (manic episodes of euphoria and overexcitement). Other common symptoms are irritability, mood swings, fatigue, muscle weakness, and problems sleeping.
Hyperthyroidism affects women more often than men. Another population especially affected are people over 60 years of age.
Its causes can be diverse; the most common cause is Gave’s disease , a type of autoimmune disorder. Other possible causes are thyroiditis, excessive iodine consumption or having thyroid nodules.
2. Hypothyroidism
Hypothyroidism would be the opposite alteration; It involves poor secretion of thyroid hormones. Specifically, the thyroid does not secrete enough thyroxine to be able to carry out the body’s functions normally
This implies alterations in the metabolism, which is deficient; Thus, the person with hypothyroidism presents weight gain (he gains weight easily), and also manifests symptoms of depression, fatigue and facial swelling, among others. Hypothyroidism, like hyperthyroidism, affects women more than men.
The causes of hypothyroidism can be several; Among them, there is a genetic form called “hereditary goiter cretinism”, in which the deficiency of thyroid hormones causes a severe delay in growth, facial malformations, alterations in sexual development and a decreased brain size and number of synaptic connections. This deficiency of thyroid hormones also causes intellectual disability.
