EVERYTHING YOU SHOULD KNOW ABOUT THE THYROID GLAND

1 in 10 people suffer from thyroid problems in Spain, these being more frequent in women .

But what is the thyroid and what diseases are related to it? Which are the most common? Today we will review the important function of this gland and what happens when it does not work properly.

The endocrine system works precisely, like a Swiss watch, and is made up of different glands (pancreas, testicles, adrenals, thyroid, etc.) that produce hormones that act as messengers for our organs and tissues.

The thyroid is a bow-tie or butterfly-shaped endocrine gland located in the neck just below the larynx. Its function is to produce the thyroid hormones T3 (triiodothyronine) and T4 (tetraiodothyronine). These hormones act on almost all the tissues of the body and help our body to use energy and maintain the basal metabolism, which is necessary to maintain vital processes when we are at rest. They affect heart rate, fertility, the central nervous system, digestive processes, calorie burning, growth and skin maintenance. The T4 hormone is the most abundant in the blood, but it is transformed in the tissues into T3, which is the active hormone.

As I said, the endocrine system works in a coordinated and precise way , and the thyroid gland is no exception. Thyroid function is controlled by the hypothalamus and the pituitary gland, so if there are not enough T3 and T4 in the blood, these glands stimulate the thyroid to produce more, and if there is not enough, they do not stimulate it to regulate the amount of hormones in the blood.

Illustration 1. Own elaboration. Canva.

An important point is that in order for these hormones to be formed and perform their function, iodine is necessary. What happens if we do not ingest enough iodine? Well, thyroid hormones are not synthesized and hypothyroidism (hypofunction of the thyroid gland) occurs.

In this situation, the pituitary gland detects that the level of thyroid hormone is too low and sends a signal to the thyroid to produce thyroid hormone and increase in size. This abnormal growth in size produces what is called " goiter ". Nowadays, goiter due to lack of iodine is not so common in developed countries thanks to the introduction of iodized salt, however, there are still areas where the deficiency continues to be a problem.

Hypothyroidism affects 20 in every 1000 women and 1 in every 1000 men , however, iodine deficiency is not the only cause of hypothyroidism.

There are other situations in which there is a decrease in the function of the gland and therefore in the levels of T3 and T4. The symptoms that accompany this decrease in the production and function of thyroid hormones are very diverse and sometimes nonspecific. Among them we find: feeling cold, tiredness, depression, mental fog or difficulty thinking, dry and rough skin, paleness, slight weight gain, memory disorders, constipation, muscle and/or joint pain, irregular menstruation, among others. This disease is underdiagnosed because some symptoms go unnoticed and over a long period of time have a great emotional impact on patients. In addition, hypothyroidism is a risk factor for other diseases, so it is important to be informed and consult a health professional if suspected, especially if there is a family history.

The most common causes of hypothyroidism are iodine deficiency, Hashimoto's thyroiditis, thyroid cancer or Graves' disease (when surgery and removal of the gland is required), drugs that cause hypothyroidism, radioiodine treatment, thyroiditis, and pituitary gland disease.

We have previously discussed hypothyroidism caused by iodine deficiency, but now I want to focus on autoimmune hypothyroidism, since it is the most common cause in our environment.

Hashimoto's thyroiditis or autoimmune hypothyroidism: as you already know, the autoimmune system protects us from infections caused by various pathogens. To do this, our lymphocytes produce antibodies that "fight" against these infectious agents. In Hashimoto's thyroiditis, lymphocytes generate antibodies against our own tissues, thus attacking the thyroid gland and producing inflammation that in the long term can result in atrophy of the gland. When this occurs, the gland becomes hypoactive, stopping the release of hormones and leading to hypothyroidism. To detect Hashimoto's thyroiditis, apart from analyzing the levels of the hormones free T3, free T4 and TSH (which the pituitary gland produces to stimulate the thyroid) in the blood, which is what we would do to see if there is hypofunction in the gland, antithyroid antibodies (Anti-TPO) and antithyroglobulin and anti-TSH receptor (TSI) are also analyzed.

There are patients who show increased TSH concentrations but normal free T4 values ​​and with mild or no symptoms. In this case it is called subclinical hypothyroidism and is often due to Hashimoto's thyroiditis. In this case, the patient would also test positive for antithyroid and antithyroglobulin antibodies.

Hypothyroidism cannot be cured, but treatment can help control it. It involves replacing the hormone that our gland does not produce with a synthetic one that performs exactly the same function in the tissues, so that T4 and TSH levels return to normal. However, in some cases treatment is not necessary.

As for lifestyle recommendations in relation to hypothyroidism, it is recommended to consume iodized salt on a regular basis, as well as selenium (which is present in many foods), zinc (which is also usually not deficient) and finally vitamin D.

During pregnancy, it is very important to control thyroid hormones well and in some cases an increase in the dose is required. Iodine supplementation also plays a crucial role since iodine deficiency affects the thyroid function of the mother and the newborn, as well as their neuropsychological development.

What happens if more thyroid hormone is produced than necessary?

Well, all the functions in which this hormone intervenes will be accelerated and this will manifest itself with different symptoms such as sweating and heat, trembling, rapid metabolism and weight loss, anxiety, nervousness, insomnia, palpitations, diarrhea, etc. This is what is known as hyperthyroidism and the most frequent cause is Graves-Basedow disease, in which the body's own antibodies are produced that stimulate the thyroid and make it produce more hormones.

Other causes may include inflammation of the thyroid, multinodular goiter, pituitary tumor, or thyrotoxicosis. Hyperthyroidism is diagnosed by analytical tests observing the concentrations of free T3, free T4, and TSH. Treatment for hyperthyroidism, whatever the cause, can be addressed with drugs that block the formation of thyroid hormones, in case of recurrences, with radioiodine, which damages the cells that produce thyroid hormones, or with surgery. In some cases, and depending on the treatment, patients may develop hypothyroidism that is easily controlled with replacement therapy.

Illustration 2. Own elaboration. Canva.

In summary, the thyroid gland plays an essential role in the functioning of the body, producing thyroid hormones that regulate various functions. Thyroid diseases, such as hypothyroidism and hyperthyroidism, are common and can have a significant impact on health. It is important to understand the importance of iodine intake, the influence of the autoimmune system, and to seek medical attention if you experience thyroid-related symptoms, as proper treatment helps control them.

If you found this topic interesting and want to delve a little deeper, I recommend that you listen to Dr. Laura Bartolomé's episode of Cristina Mitre's podcast, which is available on Spotify. Not only do they answer very common questions, but they also address other very interesting issues about this gland.

Written by Maria Caballero

Pharmaceutical

 

LITERATURE

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García Fernández, M. (2019). Hypothyroidism and its relationship with iodine deficiency (Doctoral thesis). University of La Rioja, Logroño. Available at: [ Dialnet ].

Hospital Clínic de Barcelona. (nd). Thyroid diseases. Available at: [ Clinicbarcelona.org ].

MSD. (2020). Hashimoto's thyroiditis. MSD Manuals Consumer Version. Available at: [ MSDmanuals.com ].

NIH. (2019). Iodine. Fact sheet for health professionals. Available at: [ SDG ].

Santiago-Peña, LF (2019). Physiology of the thyroid gland. Dysfunction and functional laboratory parameters in thyroid pathology. ORL Journal, 11(3), 253–257. https://doi.org/10.14201/orl.21514