Tyroxin

Tyroxin, also known as thyroxine or T4, is a thyroid hormone produced by the thyroid gland. It plays a crucial role in regulating metabolism in the body. Tyroxin affects virtually every cell and organ system, influencing growth, development, and energy expenditure. It is synthesized from the amino acid tyrosine and iodine. The thyroid gland releases tyroxin into the bloodstream, where it is transported to target tissues.

Once tyroxin reaches cells, it is converted to its more active form, triiodothyronine (T3), by enzymes called deiodinases. T3 then binds to nuclear receptors, influencing gene expression and thus controlling a wide range of metabolic processes. These include the rate at which the body burns calories, heart rate, body temperature, and the synthesis of proteins. Tyroxin is essential for normal growth and development, particularly in infants and children, affecting brain development and skeletal maturation.

The production and release of tyroxin are regulated by the pituitary gland and the hypothalamus in the brain through a negative feedback loop. When tyroxin levels in the blood are low, the pituitary gland releases thyroid-stimulating hormone (TSH), which prompts the thyroid to produce more tyroxin. Conversely, high tyroxin levels inhibit TSH release. Imbalances in tyroxin levels can lead to thyroid disorders such as hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid), both of which have significant health implications.