The Thyroid Gland – Its Physiology And Function

The thyroid gland, formerly called the thyroid gland, has an important function in our body. This endocrine gland produces two essential hormones: thyroxine or T4, and triiodothyronine or T3 . Both affect our growth and development. They are also involved in the cells’ metabolic processes and thermogenesis, or heat generation.

In addition, these hormones have an effect on the cardiovascular system, the central nervous system and the reproductive organs . Too much thyroid hormone, or lack of it, can cause various side effects in the body.

The hormones T3 and T4 are synthesized or released by the thyroid gland and the processes that take place in it. All this activity is controlled by the hypothalamus, which produces a hormone called TRH. This hormone affects the pituitary gland and stimulates the thyroid gland. The pituitary gland produces the hormone TSH, which stimulates the thyroid gland to secrete thyroid hormones into the bloodstream.

Regulation of the secretion of thyroid hormones

Hormone secretion is a process that is part of the function of the thyroid gland. Here both the hypothalamus and the pituitary gland are also involved . The process of stimulating the synthesis and secretion of thyroid hormones can be summarized in five steps:

1. TSH stimulates activity in some thyroid cells.
2. The TRH hormone reaches the pituitary gland and provides the necessary stimulus to produce the hormone TSH
3. The thyroid cells responsible for this function secrete T3 and T4 into the bloodstream, until the levels return to normal.
4. When T3 levels are high, the secretion of hormones from the hypothalamus, and thus also from the pituitary gland , is inhibited .
5. When the levels of T3 and T4 are low, signals are sent that stimulate the hypothalamus to produce the hormone TRH.

As you can see , this is an interaction between the hypothalamus, the pituitary gland and the thyroid gland itself . When we talk about the physiology of the thyroid gland in an everyday way, we can say that TSH “turns off” or “turns on” the gland.

Thyroid physiology and hormone synthesis

For the synthesis of thyroid hormones to be possible, three elements are required: iodine, thyroglobulin and thyroperoxidase . Iodine comes from external sources. It is absorbed through food and is absolutely necessary for proper thyroid function.

Thyroglobulin is a protein that is formed in the follicular cells of the thyroid gland. Thyroid oxidase, on the other hand, is an enzyme that is also produced by the thyroid gland. When the three elements are present (iodine, thyroglobulin and thyroperoxidase) , the synthesis and secretion of the thyroid hormones takes place , through four stages:

• Iodine uptake . The thyroid gland absorbs iodine that is absorbed into the body.
• Iodine is converted to organic iodine . This step includes:
  • Conversion of iodine to free iodine.
  • Free iodine is taken up by the tyrosine molecule.
  • Formation of iodothyronines.
• Composition of monoiodothyrosine (MIT) and diiodothyrosine (DIT) to T3. And composition of two DIT to form T4, thanks to the function of thyroid peroxidase.
• Secretion of thyroid hormones . This is the process by which thyroid hormones are released into the bloodstream. This stage is regulated by the hormone TSH in the pituitary gland.

As you can see , thyroid physiology is a complex and laborious process . If errors occur throughout this system, diseases such as hyperthyroidism or hypothyroidism (high or low metabolism) can occur.

Thyroid hormone function

Thyroid hormones are essential for proper functioning of the body. They intervene in many ways . Among the most important features are:

• They increase the oxygen supply to the tissue, thus helping to regulate heart function.
• They increase the absorption of proteins and carbohydrates in the digestive tract.
• They contribute to the development of the fetus, and growth in childhood.
• They facilitate the body’s ability to transport oxygen.
• They regulate blood pressure and body temperature.
• They promote normal growth of nerve cells.
• They facilitate the synthesis of proteins and glycogen.
• They promote the absorption of fats.

In short, the thyroid hormones play an important role in metabolism. We can more or less say that they regulate the energy processes and optimize them , especially in periods when the body changes.