Physiology Of The Thyroid

For the thyroid to function properly, regular intake of iodine in the diet is required.

The physiology of the thyroid is fundamental for the organism.

This endoctrin gland produces two determining hormones: thyroxine or T4 and triiodothyronine or T3. Both have an influence on the regulation of growth and development.

They are also involved in cell metabolism and thermogenesis or heat generation.

Likewise, thyroid hormones impact the cardiovascular system, central nervous system, and reproductive organs. The excess and defect of thyroid hormones cause various adverse effects on the body.

The hormones T3 and T4 are synthesized or released from processes involved in the physiology of the thyroid. All of this activity is controlled by the hypothalamus, which produces a hormone called TRH which acts on the pituitary gland and stimulates the thyroid.

The pituitary gland, in turn, is the source of the hormone HRT, which causes the thyroid to secrete thyroid hormones into the blood.

Control of the secretion of thyroid hormones

The secretion of hormones is a process in the physiology of the thyroid. It involves the participation of the hypothalamus and pituitary gland.

The way in which the stimulation of synthesis and release of thyroid hormones is carried out can be summarized in five steps:

1. HRT stimulates the activity of certain thyroid cells.
2. The THR hormone reaches the pituitary gland and generates the stimulus necessary to produce the THS hormone.
3. The thyroid cells responsible for this function release T3 and T4 into the blood, until the levels return to normal.
4. When T3 levels are high, hormone release is inhibited by the hypothalamus and, therefore, the pituitary gland.
5. When T3 and T4 levels are low, signals are produced to stimulate the hypothalamus to produce the hormone THR.

As can be seen, it is a feedback process between the hypothalamus, pituitary gland and the thyroid gland itself. Speaking of the thyroid more colloquially, you could say that HRT is “active” or “inactive” on the gland.

Thyroid physiology and hormone synthesis

To be able to synthesize thyroid hormones, it is necessary to have three elements: iodine, thyroglobulin and thyroperoxidase.

Iodine comes from external sources. It is acquired through food and is absolutely necessary for the proper functioning of thyroid physiology.

Thyroglobulin is a protein that forms in the follicular cells of the thyroid. On the other hand, thyroperoxidase is an enzyme which is also produced by the thyroid.

When all three elements (iodine, thyroglobulin and thyroperoxidase) are present, the process of synthesis and release of thyroid hormones takes place in four stages:

• The absorption of iodine. The thyroid catches the surrounding iodine.
• Conversion of iodide to organic iodine. This step includes:
  • Conversion of free iodine iodide. Incorporation of free iodine into the tyrosine molecule. Formation of iodothyronines.
• Coupling of monoiodotyrosine (MIT) and diiodotyrosine (DIT) to create T3. And coupling of two DITs to form T4, thanks to the action of tiroperoxidase.
• Secretion of thyroid hormones. It is the process by which thyroid hormones are released into the blood. This stage is regulated by the HRT hormone from the pituitary gland.

As can be seen, the physiology of the thyroid is a complex, millimeter-scale process. The dysfunction of this whole system can give rise to diseases such as hyperthyroidism or hypothyroidism.

Action of thyroid hormones

Thyroid hormones are essential for the proper functioning of the body. They intervene in several ways, among which the following stand out:

• Increase the supply of oxygen to tissues, thus helping to regulate heart function.
• Increase the absorption of proteins and carbohydrates in the digestive tract.
• Also involved in the development and growth of the fetus during childhood.
• Facilitate the body’s ability to transport oxygen.
• Regulate blood pressure and body temperature.
• Also promote the normal growth of neurons.
• Facilitate the synthesis of proteins and glycogen.
• Promote fat absorption.

In summary, thyroid hormones play a fundamental role in metabolism. They fundamentally regulate energy processes and optimize them, especially in the stages of change.