A tireless "worker" coordinating the functioning of metabolism, growth and development. What is the role of the thyroid gland in our body?

Thyroid hormones affect the rate of metabolism in two ways:

1. They stimulate almost all tissues in the body to produce proteins,
2. They increase the amount of oxygen that these tissues then use (1).

Thyroid hormones affect vital bodily functions, such as heart rate, calorie burning rate, skin health, growth, thermoregulation, fertility, and digestion (1). Learn how thyroid hormones work, allowing you to live a full, unrestricted life.

The hormones thyroxine (T4) and triiodothyronine (T3) regulate the body’s metabolic processes

The thyroid gland—an endocrine gland—is responsible for the production and secretion of thyroid hormones and iodine homeostasis. It produces approximately 90% of the inactive hormone thyroxine (T4) and 10% of the active hormone triiodothyronine (T3). The inactive T4 is then peripherally activated to T3. (2) The hormones produced by the thyroid gland help regulate metabolism, the chemical processes in the body that transform what you eat into energy. They affect, for example, how fast your heart beats, how deeply you breathe, and whether you gain or lose weight. (3)

T3 and T4 also control body temperature, cholesterol levels, and the menstrual cycle in women.

The thyroid gland is stimulated to release hormones into the bloodstream by a hormone (TSH, thyroid-stimulating hormone, thyrotropin), which is produced by the anterior lobe of the pituitary gland (3).

The thyroid gland produces and secretes the following hormones:

1. thyroxine (T4): the primary hormone produced and released by the thyroid gland. Once released into the bloodstream, it is converted to T3 in peripheral tissues (especially tissues with high blood flow, such as the liver and kidneys) by a process called deiodination (4);
2. triiodothyronine (T3): although produced in smaller quantities by the thyroid gland, it is the biologically active form of the thyroid hormones and therefore has a direct effect on metabolism. Most of it is derived from thyroxine (T4) (4);
3. reverse triiodothyronine (rT3): the thyroid gland also produces a small amount of rT3 or the inactive form of T3; when needed (when its effects are not desired), its production is increased at the expense of T3 (4);
4. calcitonin: a hormone that regulates the amount of calcium in the blood; it is produced in a different type of thyroid cell than thyroid hormones (4).

Ten functions of the thyroid gland that affect the proper functioning of metabolism

Thyroid hormones affect practically all nuclear cells in the human body. They affect their growth, development and metabolism, stimulating them.

1. Thyroid hormones accelerate the heart rate (resting rate) using the so-called positive chronotropic effect (2) (5).
2. Thyroid hormones increase the force of cardiac contraction by triiodothyronine (T3) increasing the amount of intracellular calcium in the myocardium; this mechanism is also used in accelerating the heart rate. The increased force of cardiac contraction leads to an increase in stroke volume and, in combination with accelerated heart rate, to an increase in the volume of blood pumped into the body by the heart per unit time (2) (5).
3. Thyroxine affects basal metabolism, heat production and oxygen consumption in cells.
4. Thyroid hormones promote the oxidation of glucose and fatty acids, resulting in increased thermogenesis and increased heat dissipation. Increased heat production is compensated for by increased vascular blood flow, sweating, and ventilation, all of which are also influenced by thyroid hormones (2) (5).
5. T3 stimulates resting respiratory rate and minute ventilation (the number of breaths per minute and the total amount of air inhaled per minute), thereby helping to maintain normal blood oxygen levels. It also stimulates the production of erythropoietin and hemoglobin, thereby supporting the supply of oxygen to tissues (2) (4) (5).
6. Thyroid hormones promote the absorption of folate and cobalamin in the gastrointestinal tract (2) (5).
7. T3 is responsible for fetal development and bone growth, ossification and maturation of bone centers after birth (2) (4) .
8. T3 stimulates the nervous system, increasing alertness and responsiveness to external stimuli. It also affects the peripheral nervous system, reflexes, gastrointestinal tone and motility (2) (5).
9. Thyroid hormones affect reproductive health, the ovulatory cycle and spermatogenesis (2) (4) (5).
10. Thyroid hormones affect the activity of the pituitary gland - they support the production and release of growth hormone and at the same time inhibit the production of the hormone prolactin (2) (5).

Hypothyroidism and hyperthyroidism – when the thyroid gland is underactive or overactive

The thyroid gland works as it should, until it suddenly stops working. This manifests itself as either hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid) (6).

Hypothyroidism can be caused by:

1. Hashimoto’s disease: an autoimmune disease that causes the thyroid gland to underactive. The body makes antibodies against the thyroid gland, which interfere with the production of its hormones by blocking important enzymes. This is the most common cause of hypothyroidism in countries where iodized salt is readily available (6) (7).
2. Iodine deficiency: The thyroid gland needs iodine to produce thyroid hormones, and a deficiency of iodine leads to hypothyroidism. This is the most common cause of hypothyroidism in countries where iodized salt is readily available. Thyroid dysfunction caused by iodine deficiency often causes a so-called hypofunctional goiter (enlarged thyroid gland) (6) (8).
3. Congenital hypothyroidism: approximately one in 2,000 to 4,000 babies is born with a missing or underactive thyroid gland (6).
4. Disorders of regulatory centers: functional or mechanical disorders of the pituitary gland and hypothalamus.

Hyperthyroidism can be caused by:

1. Graves’ disease: also known as toxic diffuse goiter, is a chronic autoimmune disease accompanied by hyperthyroidism. It is the most common cause of hyperthyroidism (6) (9). In this disease, the body produces antibodies that mimic thyroid hormones. The thyroid gland produces too many hormones, which leads to hyperthyroidism. It often enlarges, creating a so-called diffuse goiter.
2. Thyroid nodules: These are small growths or lumps that can be either fluid-filled or solid. They are usually harmless and do not cause serious problems. Only a small number of them can be cancerous, in which case they should be treated immediately. If the nodules are hyperfunctioning, they lead to hyperthyroidism (6) (10).
3. Excessive iodine intake: Too much iodine in the body stimulates the thyroid gland to produce more hormones than necessary. Excess iodine does not enter your body through excessive salt intake, but rather through the use of certain medications containing this mineral (6) (4).
4. Disorders of the regulatory centers: the pituitary gland and the hypothalamus.

Thyroid dysfunction is indicated by, for example, excessive thirst, sweating or goiter

Hyperthyroidism (= overfunction) can be assumed on the basis that an excess of thyroid hormones throws a number of processes in the body out of balance, and this can be manifested by:

• palpitations and rapid heartbeat,
• high blood pressure,
• weight loss despite an increased appetite,
• diarrhea,
• tremors, irritability, sleep problems,
• weakness and fatigue,
• excessive sweating and constantly hot and humid skin (11) (12).

Depending on the specific cause of the increased production or release of thyroid hormone (hyperthyroidism), a goiter, either diffuse or nodular, may appear.

Hypothyroidism (= underfunction) is characterized by insufficient production of thyroid hormones, which slows down the entire metabolism. You can recognize it by the fact that the processes that thyroid hormones regulate are suppressed or “slowed down,” which is manifested by:

• weakness and fatigue,
• weak pulse,
• shortness of breath,
• problems with concentration or memory,
• lethargy,
• depression,
• dry skin,
• a low, hoarse voice,
• constipation,
• reduced fertility,
• erectile dysfunction (11) (13).

How do you recognize a thyroid disorder? Take a simple laboratory test that, among other things, will reveal insufficient or excessive production of thyroid hormones

Supporting thyroid function does not only mean supplementation with vitamin D, zinc, selenium and magnesium, but also regular laboratory tests of this organ. The reality is unfortunately that people do not notice thyroid disorders for a long time due to their non-specific and often mild symptoms. As with other diseases, the sooner they are detected, the better they can be treated. In this case, a blood test is the only possible option to detect a thyroid disorder.

The test, which you can take at any time, even during pregnancy, will show you how your thyroid gland is working. A properly functioning thyroid gland is essential for a healthy and fulfilling life.

It is recommended that women over the age of 50 undergo a check-up every four years, people with other autoimmune diseases (primarily type 1 diabetes, celiac disease, and others) once a year, and women before a planned pregnancy and in the first trimester of pregnancy (14). If a thyroid disorder is suspected after a negative laboratory test, a check-up is recommended every two years (15).

The thyroid gland is a key organ responsible for producing hormones that regulate metabolism and energy balance in the body. Disorders such as hypothyroidism or hyperthyroidism can lead to a variety of problems, such as fatigue, weight changes, heart problems, and psychological discomfort. Do not underestimate regular thyroid examinations, which help to detect potential problems early and prevent more serious health complications.