Thyroxine: What It Is and Associated Diseases
Thyroxine is one of the most important hormones in the human body. Hormones are a series of substances that are synthesized in the glands, and whose main function is to maintain the homeostasis or balance of our organism. Unfortunately, a variety of diseases are associated with these substances.
Most of the conditions result from an error in the synthesis or release processes. This will consequently alter the concentration in the bloodstream, and they won’t carry out their function properly.
What is thyroxine?
Also known as tetraiodothyronine or T4, thyroxine is a hormone made by iodine, which is synthesized and released from a gland located in the back of the neck. It has a particular chemical structure, composed by condensing the amino acid tyrosine and adding 2 atoms of iodine.
The amount of T4 produced in this gland is much greater than other synthesized hormones, but it’s not very active biologically. Multiple studies have established that thyroxine behaves like a peripheral prohormone, i.e. it must be transformed into its active form by enzymatic action.
The hypothalamus and the pituitary gland regulate the secretion of tetraiodothyronine. Both structures synthesize substances capable of stimulating or inhibiting the release of T4, depending on the requirements of the organism.
Which gland is responsible for producing thyroxine?
The thyroid gland is responsible for producing and releasing thyroxine into the bloodstream. It’s located in the back of the neck, just below the larynx, and in front of the trachea. The anatomy of the thyroid resembles a shield: it consists of two lobes located on either side of the trachea, and joined by a central region called the isthmus.
Under normal conditions, this gland weighs about 20 grams and is usually not palpable. Its main function is the production of different hormones, among which T4 or thyroxine and T3 or triiodothyronine are the most important.
Specialized structures in the thyroid gland called follicles are responsible for synthesizing thyroid hormones. At the center of these follicles is a colloid substance that contains everything necessary for hormone production. As such, the colloid contains enzymes, iodine, tyrosine, and a special protein: thyroglobulin.
Read also: 6 Signs to Identify Thyroid Problems
What’s the function of this hormone?
The main function of thyroid hormones is related to the metabolism and growth of the human body. However, thyroxine is less biologically active and has a longer half-life than triiodothyronine. These characteristics make T4 the ideal substance for maintaining a constant reserve.
In general terms, triiodothyronine is the active form of the thyroid hormones, while thyroxine functions as the plasma reserve. When the body has low levels of T3, various enzymes in the peripheral tissues extract an iodine atom from thyroxine, transforming it into its active form.
Studies have established that thyroid hormones play a very important role, even from the beginning of life in the uterus. They’re essential for regulating the development and growth of human beings. In this context, they have the following functions:
- Promotion of cognitive development
- Regulation of cellular metabolism
- They aid in the production of energy
- Maintenance of the function of the musculoskeletal system
- They participate in bone metabolism
- They alter the functioning of the cardiovascular and digestive systems
Diseases related to thyroxine deficiency
The most common condition related to thyroxine and triiodothyronine deficiency is hypothyroidism. This is a disease that’s defined by decreased thyroid hormone effect at the tissue level. The most common cause is a decrease in the production or release of thyroid hormones, although it can also develop due to peripheral resistance.
Hypothyroidism can be primary or secondary. It’s called primary when there’s a dysfunction in the gland itself, and central or secondary when decreased secretion of the releasing factors happens at the level of the pituitary gland or hypothalamus.
The main causes of hypothyroidism include the following:
- Hashimoto’s disease
- Radiotherapy treatment and certain medications
- Too much or too little iodine in the body
A deficiency of thyroid hormones can cause another condition called goiter, which is an increase in the size of the thyroid gland. This increase in volume happens in order for it to be able to capture more iodine and increase production.
Find out more: The Causes of Low Thyroid Stimulating Hormone
Diseases related to excess thyroxine
Excess thyroxine and triiodothyronine in the bloodstream is known as hyperthyroidism. It can be caused by a variety of conditions that alter the functioning of the gland and increase hormone production.
Among the main diseases that can cause hyperthyroidism are the following:
- Graves-Basedow disease
- Toxic multinodular goiter
- Toxic adenoma
This condition can increase the basal metabolism of the human body, so that all the functions of the organism accelerate. As a result, the sufferer may experience palpitations, nervousness, weight loss, and increased sweating.
Pregnancy can also cause an increase in thyroid hormone levels, especially in the first trimester. However, this increase is physiological.
Thyroxine: an essential hormone for the body
Thyroxine is a hormone produced in the thyroid gland that can be transformed to its active form in peripheral tissues, which means it’s a reserve source. Thyroid hormones perform essential functions within the body, almost all of which are related to the regulation of basal metabolism and growth.
Diseases associated with an excess or deficit of thyroxine alter the basal metabolism, causing uncomfortable and dangerous symptoms. Of course, timely diagnosis and treatment of these diseases will ensure correct management and prevent complications.It might interest you...