Thyroid hormones: types and functions in the human body.

These thyroid hormones are involved in metabolic processes in the body.

The endocrine system consists of all those glands and hormones that act in our organism. Hormones have a very important role in the regulation of basic physiological processes; moreover, they are also especially related to emotions.

In this article we will talk about thyroid hormones, a type of hormones synthesized by the thyroid glands.Thyroid hormones, a type of hormones synthesized by the thyroid gland and involved in metabolism. We will learn about their origin, characteristics and functions. In addition, we will analyze two important alterations that occur in the thyroid: hyperthyroidism and hypothyroidism.

Thyroid hormones: characteristics

Thyroid hormones are a type of hormones secreted in our body, 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.

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, noradrenaline, melatonin and dopamine. Interestingly, the latter substances are both neurotransmitters (within the Central Nervous System [CNS]) and hormones (outside it).

But how do amine hormones work? What they do is bind to receptors on the cell membrane, initiating a chain reaction in the cell. Let's take a look at 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.

In terms of function, thyroxine mainly stimulates the body's metabolism and is involved in other processes.It also participates in other processes. It is important for proper functioning that thyroxine levels are adequate and balanced, as too high or too low levels can cause disturbances throughout the body.

This is what happens when thyroid disorders occur: hyperthyroidism (increased thyroid hormones) and hypothyroidism (decreased 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 also plays a central role in the control and regulation of the body's metabolism.. It stimulates the metabolism of carbohydrates and fats by activating oxygen consumption.

In addition, triiodothyronine is also involved in different is also involved in various physiological processes in the body, such as growth, heart rate and body temperature (like thyroxine). (just like thyroxine). Finally, another function it performs is that of degrading proteins within cells.

Where do thyroid hormones come from?

To understand where thyroid hormones come from, we will have to visualize a global scheme of hormones and the endocrine system. The endocrine system is headed by the hypothalamus, the main secreter of thyroid hormones.the main hormone secreting and "commanding" structure, connecting the nervous system with the endocrine system. The latter, in turn, originates 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" for these hormones.

To be more specific, the adenohypophysis produces the trophic hormones, which in turn act on the glands; these glands produce the different hormones in the organism. This is what happens with the thyroid hormones: they are synthesized by the gland. are synthesized by the thyroid gland, which in turn receives signals from the adenohypophysis (a part of the hypothalamus). (a part of the hypothalamus, the anterior part).

In other words, 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. To summarize, what these structures (TSH and thyrotropin) actually do is to 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 nut.just above the clavicle and below the nut.

It is not a very large structure, and weighs about 30 grams. The thyroid plays an essential role in the metabolism of our body, as well as in other body functions such as body temperature. In addition, its condition and function are closely related to each other, its condition and function 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:

• Participation in growth.
• Regulation of metabolism.
• Regulation of body temperature.
• Development of the nervous system.
• Assimilation of nutrients.
• Regulation of heart rate.
• Development of the skin.

Alterations

There are two important alterations in the thyroid glandThe main symptoms of thyroid hormone secretion are: hyperthyroidism and hypothyroidism.

Hyperthyroidism

Hyperthyroidism consists of an elevated secretion of thyroid hormones; specifically, secretes too much thyroxine. This means that the thyroid is overactive and as a consequence, the body's metabolism is accelerated.

This causes significant weight lossas well as rapid and/or irregular heartbeat. It is associated with symptoms of hyperarousal and mania (manic episodes of euphoria and overexcitement). Other common symptoms are irritability, mood swings, fatigue, muscle weakness and sleep problems.

Hyperthyroidism affects women more often than men. Another population particularly affected is people over 60 years of age.

Its causes can be diverse; the most common cause is Gave's disease, a type of autoimmune disorder.a type of autoimmune disorder. Other possible causes are thyroiditis, excessive iodine intake or having thyroid nodules.

2. Hypothyroidism

Hypothyroidism would be the opposite alteration; it implies a poor secretion of thyroid hormones. Specifically, the thyroid does not secrete enough thyroxine to be able to develop the functions of the organism with normality..

This implies alterations in the metabolism, which is deficient; thus, the person with hypothyroidism presents an increase in weight (he/she puts on weight easily), and also manifests depressive symptoms, fatigue and swelling of the face, among others. Hypothyroidism, like hyperthyroidism, affects women more than men.

The causes of hypothyroidism may be several; among them, there is a genetic form called "hereditary goitrous cretinism", in which the deficit of thyroid hormones causes severe growth retardation, facial malformations, alterations in sexual development and a decreased brain size and number of synaptic connections. This thyroid hormone deficiency also causes intellectual disability.

Bibliographical references:

• Carlson, N.R. (2005). Physiology of behavior. Madrid: Pearson Educación.
• Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.