The most common method for evaluating the thyroid condition is to determine the amount of hormones in the blood serum. Every endocrinologist uses it to diagnose the health status of patients. Read this article and find out more about the thyroid, the importance of its hormones, as well as popular thyroid gland function tests.
What is Thyroid Gland
The thyroid is the main endocrine gland located in the front of the neck, just below the Adam’s apple. It is shaped like a butterfly’s wings and produces iodine-containing hormones. The general weight of the thyroid in a healthy adult should not exceed 35 g.
As for the functions, the thyroid gland is responsible for the healthy functioning of the entire body. Failure in its work can lead to serious negative consequences such as Hashimoto’s thyroiditis, hyperthyroidism, hypothyroidism, inflammation, goiter (GOI-tur), and cancer.
What are Thyroid Hormones
Triiodothyronine and Thyroxine (Tetraiodothyronine) are the two basic thyroid hormones. They have some distinctive characteristics. But the main feature is that Triiodothyronine contains 3 iodine molecules, and thyroxine hormone – 4 molecules. In this regard, they are often called T3 and T4.
Thyroxine (T4)
Thyroxine accounts for up to 90% of the total amount of hormones released by the thyroid. It is found in the blood in a free or protein-bound form. Most of the T4 hormone is protein-bound, and about 0.1% remains free. Free Thyroxine allows to assess the thyroid function regardless of the general concentration of T4-binding proteins in the blood.
The lack of T4 provokes the development of symptoms typical of hypothyroidism:
- Increase in body weight;
- Sensitivity to cold;
- Xeroderma;
- Tiredness;
- Menstrual cycle dysfunction.
An excess amount of the hormone provokes the development of hyperthyroidism and, as a result, causes an acceleration of metabolic processes, weight loss, hand tremor, sleep problem, restlessness, and rapid heartbeat.
Triiodothyronine (T3)
Produced by the thyroid, T3 is metabolically more active than T4. The T3 hormone level in the blood is approximately 5% of the general concentration of all thyroid hormones.
The action of Triiodothyronine is based on its direct contact with blood proteins and circulation in an inactive state. Any change, whether it is an increase or decrease in blood protein concentration (pregnancy, kidney or liver disease), causes a change in the concentration of total T3 in the bloodstream. This, in turn, temporarily affects the concentration of free T3. Consequently, the production of this hormone by the thyroid also undergoes changes until its level reaches normal indicators.
Role of Thyroid Hormones
Thyroid hormones have a variety of effects. They bind to the nuclear receptors of cells, which determines their participation in almost all body processes.
Regulation of Metabolic Rate
Regulation of metabolic rate is one of the key functions of the thyroid. If the gland works without deviations, the metabolic rate is also within normal limits. Hypothyroidism is usually accompanied by a decrease in metabolic rate, fluid retention, and weight gain. Hyperthyroidism is characterized by an accelerated metabolic rate and weight loss.
Growth and Development
Thyroid hormones have a significant impact on growth and development. They determine mental abilities, body weight, physical activity, sexual development, muscle and bone strength, skin and hair condition. Abnormal thyroid does not perform these functions well.
Body Temperature
A regular increase or decrease in body temperature is one of the first signs of thyroid disorder. Practice shows that hypothyroidism usually causes a drop in temperature, while hyperthyroidism provokes its increase.
Heart Rate
An overactive thyroid type can cause chest pain and fast heart rate. Arrhythmia and tachycardia may even develop. These factors significantly increase the risk of heart attack.
Other
The thyroid gland one way or another affects all systems of the body including the nervous, cardiovascular, muscular, reproductive, and digestive. Therefore, when thyroid diseases occur, they must be treated immediately.
Thyroid Hormone Production and Regulation
Thyroid hormone regulation is a well-coordinated process. In short, the synthesis of T3 and T4 is directly determined by the amount of iodine that enters the body from food. The hypothalamus sends signals to the pituitary gland (hypophysis) and thus regulates the amount of hormonal substances released. Read more about this below.
Hypothalamus-Pituitary-Thyroid (HPT)
The release of thyroid hormones is tightly controlled by the hypothalamic-pituitary-thyroid (HPT) axis. In response to various environmental and physiological stimuli, neurons of the small cell paraventricular nucleus secrete thyrotropin releasing hormone (TH-releasing hormone), which encourages the anterior pituitary gland to produce thyroid stimulating hormone.
Thyroid-Stimulating Hormone (TSH)
The normal TSH interacts with follicle epithelial cell membrane receptors and induces thyroid hormone secretion through intermediaries. The result is the uptake of iodide by the thyroid, the enhanced synthesis of thyroglobulin, the hydrolysis of thyroglobulin, as well as the secretion of T4 and T3 into the blood.
Thyroid Function Tests
In cases when the hypothalamus and thyroid gland produce too much or too little hormones, various pathological processes (for example, a tumor) can develop. Thus, timely diagnosis of levels high low is important. Testing the state of the endocrine gland is usually carried out on the basis of a general blood test, a general urine test with automatic sediment microscopy, glycosylated hemoglobin, free T4, TSH, thyroid peroxidase antibodies (TPO), etc. A detailed patient examination allows the doctor to prescribe the most appropriate medication.
Summary
It is difficult to overestimate the role that thyroid hormones play in the human body. They ensure normal development, metabolism, bloodstream, body temperature, and a variety of other processes. Insufficiency of hormones causes a slowdown in metabolism, a decrease in memory and attentiveness, an increase in body weight, etc. An excess level of thyroid gland hormones leads to a faster metabolism, weight loss, mood swings, heart arrhythmias, etc.
Thus, every person should control the thyroid condition and undergo effective treatment in case of abnormalities.
FAQ
What do thyroid hormone levels do?
Thyroid hormones affect metabolism, heat generation, oxygen uptake, and pulse rate. They are also responsible for the proper functioning of the gastrointestinal tract, the work of the nervous system, etc.
What happens when thyroid hormones are too high?
High thyroid levels speed up metabolism, which leads to weight loss. Increased irritability, fussiness, insomnia, sweating, hand tremors, and heart palpitations are also possible.
What are the 3 hormones of the thyroid and their functions?
The thyroid produces thyroxine (T4), triiodothyronine (T3), and calcitonin. They stimulate tissue growth, increase the cell’s demand for oxygen, regulate heart rate, etc.
What are T3 and T4 hormones and TSH?
T3 and T4 are the key thyroid hormones that regulate the body’s energy production, the metabolism of fats, proteins, and microelements. The TSH hormone regulates the flow of iodine into the thyroid gland and improves lipolysis (the breakdown of fats into fatty acids).
