Týroxín

Týroxín, also known as thyroxine or T4, is a thyroid hormone produced by the thyroid gland. It plays a crucial role in regulating metabolism, growth, and development in the human body. Týroxín is synthesized from tyrosine and iodine within the thyroid follicular cells. Its release into the bloodstream is regulated by the pituitary gland's secretion of thyroid-stimulating hormone (TSH).

Once in circulation, týroxín acts on nearly every cell in the body. Its primary function is to increase the basal metabolic rate, which is the rate at which the body burns calories at rest. This effect helps to regulate body temperature, heart rate, and energy expenditure. Týroxín is also essential for normal growth and development, particularly in children, influencing bone growth, brain development, and sexual maturation.

The level of týroxín in the blood is tightly controlled through a negative feedback loop. When T4 levels are low, the pituitary releases more TSH, stimulating the thyroid to produce more hormone. Conversely, high T4 levels lead to decreased TSH secretion. Imbalances in týroxín production can lead to various thyroid disorders. Hypothyroidism, a condition of insufficient týroxín, can cause fatigue, weight gain, and slowed metabolism. Hyperthyroidism, characterized by excessive týroxín, can lead to weight loss, rapid heart rate, and anxiety. Medical professionals often measure týroxín levels, along with TSH, to diagnose and monitor thyroid conditions.