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In any case, the concentration of T 3 in the human blood plasma is about one-fortieth that of T 4. The half-life of T 3 is about 2.5 days. [3] The half-life of T 4 is about 6.5 days. [4] T 3 levels start to rise 45 minutes after administration and peak at about 2.5 hours.
The major form of thyroid hormone in the blood is thyroxine (T 4), whose half-life of around one week [4] is longer than that of T 3. [5] In humans, the ratio of T 4 to T 3 released into the blood is approximately 14:1. [6] T 4 is converted to the active T 3 (three to four times more potent than T 4) within cells by deiodinases (5′-deiodinase).
Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. [ 3] Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism. [ 3] Some, however, use the terms interchangeably. [ 5]
Normal human body temperature ( normothermia, euthermia) is the typical temperature range found in humans. The normal human body temperature range is typically stated as 36.5–37.5 °C (97.7–99.5 °F). [ 8][ 9] Human body temperature varies. It depends on sex, age, time of day, exertion level, health status (such as illness and menstruation ...
Thyroid disease is a medical condition that affects the function of the thyroid gland. The thyroid gland is located at the front of the neck and produces thyroid hormones [ 1] that travel through the blood to help regulate many other organs, meaning that it is an endocrine organ. These hormones normally act in the body to regulate energy use ...
The hypothalamic–pituitary–thyroid axis ( HPT axis for short, a.k.a. thyroid homeostasis or thyrotropic feedback control) is part of the neuroendocrine system responsible for the regulation of metabolism and also responds to stress. As its name suggests, it depends upon the hypothalamus, the pituitary gland, and the thyroid gland .
Human thermoregulation. As in other mammals, human thermoregulation is an important aspect of homeostasis. In thermoregulation, body heat is generated mostly in the deep organs, especially the liver, brain, and heart, and in contraction of skeletal muscles. [ 1] Humans have been able to adapt to a great diversity of climates, including hot ...
Thyroid follicular cells (also called thyroid epithelial cells or thyrocytes[ 1]) are the major cell type in the thyroid gland, and are responsible for the production and secretion of the thyroid hormones thyroxine (T 4) and triiodothyronine (T 3 ). They form the single layer of cuboidal epithelium that makes up the outer structure of the ...