Thyroid Gland Function – What is thyroid – Secretion – Hypothyroidism and Hyperthyroidism

Thyroid Gland Function: The Gland is a fundamental gland for the proper functioning of the body, being responsible for the synthesis of T3, T4 and calcitonin.

The thyroid is an important gland in the endocrine system . It has the shape of a butterfly and synthesizes two hormones : T3 (triiodothyronine) and T4 (thyroxine) , which act in metabolism. For the synthesis of these hormones, the thyroid requires iodine . To avoid the deficiency of this mineral in the population, common table salt is currently supplemented with sodium iodide.

Thyroid Gland Function

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The secretion of thyroid hormones is controlled by a hormone secreted by the anterior pituitary gland called thyroid-stimulating hormone or TSH. In addition to T3 and T4, the Gland is also responsible for releasing calcitonin , a hormone that plays a role in calcium metabolism.

What is thyroid?

The thyroid is an endocrine gland made up of two lobules , which are joined by a ribbon of glandular tissue (isthmus). The gland is located immediately below the larynx and each lobe is arranged on one side of the trachea. In an adult individual, it weighs about 20 to 30 grams. It is worth mentioning that it is encapsulated by two layers of connective tissue .

This gland is made up of two lobes and is shaped like a butterfly.

The Gland is made up of several thyroid follicles, which have a diameter of about 0.2 to 0.9 mm. Each follicle consists of a layer of cubic cells that surrounds a cavity, which contains a gelatinous substance known as a colloid.

Colloid is mainly made up of a glycoprotein called thyroglobulin, which contains the hormones T3 and T4. Follicular cells take up the colloid by endocytosis and a series of reactions take place in order to release T3 and T4 into the cytoplasm. Hormones cross the cell membrane and diffuse into the capillaries.

Thyroid Gland Function

It also contains parafollicular cells or thyroid C cells, which are responsible for the production of the hormone calcitonin. The secretion of this hormone is activated when there is an increase in blood calcium concentration.

Secretion of thyroid hormones

The secretion of T3 and T4 hormones is increased due to the action of the hormone TSH, the thyroid-stimulating hormone. When levels of thyroid hormones in the blood fall below normal levels, the hypothalamus secretes thyrotropin-releasing hormone (TRH), which acts on the pituitary gland, inducing it to secrete TSH. TSH then stimulates the release of thyroid hormones. When there is an increase in thyroid hormones in the body and they return to normal levels, there is a reduction in TSH secretion by the pituitary gland and, in this way, the body’s balance with adequate hormone amounts is maintained.

Thyroid Gland Function

Thyroid Gland Function: The thyroid is an endocrine gland that produces the hormones thyroxine (T4), triiodothyronine (T3) and calcitonin. The T3 and T4 hormones are generally related to the regulation of metabolism in the body.

This hormones act, for example, on:

  • growth;
  • stimulation of carbohydrate and lipid metabolism;
  • increased basal metabolism;
  • body weight reduction;
  • increased blood flow;
  • increased cardiac strength;
  • increased production of digestive secretions and gastrointestinal tract motility;
  • increased speed of thought , etc.

Calcitonin is a hormone related to the reduction of blood calcium, with the main effect of inhibiting bone tissue resorption.

Hypothyroidism and Hyperthyroidism

The thyroid often does not work properly, and there may be an increase in hormone production or a drastic reduction in the production of these hormones. When thyroid hormones are produced in insufficient amounts, we have a case of hypothyroidism , and when production is excessive, we have a case of hyperthyroidism.

Hyperthyroidism can have different causes, the most common being Graves’ disease, an autoimmune disease that leads to thyroid malfunction. In the case of hypothyroidism, the main cause is also an autoimmune disease known as Hashimoto ‘s thyroiditis.

Goiter is the enlargement of the thyroid gland and can occur in cases of hypothyroidism and hyperthyroidism.

The Brazilian Society of Endocrinology and Metabology highlights as symptoms of hypothyroidism:

  • slower heartbeat;
  • intestinal malfunction;
  • growth commitment;
  • memory reduction;
  • tiredness;
  • muscle and joint pain;
  • somnolence;
  • dry skin;
  • weight gain;
  • high cholesterol;
  • depression.

Also according to the Brazilian Society of Endocrinology and Metabology, in the case of hyperthyroidism , the following symptoms stand out:

  • weight loss;
  • accelerated heartbeat;
  • diarrhea and frequent bowel movements;
  • agitation;
  • compromised sleep;
  • the person feels very energetic despite being tired all the time.

It is worth noting that, in both hyperthyroidism and hypothyroidism, an increase in the volume of the thyroid gland may occur, leading to the formation of a goiter.

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