"Tien Shinhan"
(Thyroid-stimulating hormone)
1. T3 (Triiodothyronine)
T3 increases the basal metabolic rate and thus, increases the body's oxygen and energy consumption.
> Basal metabolic rate - the minimal caloric requirement needed to sustain life in a resting individual.
T3 acts on the majority of tissues within the body, with a few exceptions including the spleen and testis. It increases the production of the Na+/K+ -ATPase and, in general, increases the turnover of different endogenous macromolecules by increasing their synthesis and degradation.
> Basal metabolic rate - the minimal caloric requirement needed to sustain life in a resting individual.
T3 acts on the majority of tissues within the body, with a few exceptions including the spleen and testis. It increases the production of the Na+/K+ -ATPase and, in general, increases the turnover of different endogenous macromolecules by increasing their synthesis and degradation.
Protein
T3 stimulates the production of RNA Polymerase I and II and, therefore, increases the rate of protein synthesis. It also increases the rate of protein degradation, and, in excess, the rate of protein degradation exceeds the rate of protein synthesis. In such situations, the body may go into negative ion balance.
Glucose
T3 potentiates the effects of the β-adrenergic receptors on the metabolism of glucose. Therefore, it increases the rate of glycogen breakdown and glucose synthesis in gluconeogenesis.
Lipids
T3 stimulates the breakdown of cholesterol and increases the number of LDL receptors, therefore increasing the rate of lipolysis.
Heart
T3 increases the heart rate and force of contraction, thus increasing cardiac output, by increasing β-adrenergic receptor levels in myocardium. This results in increased systolic blood pressure and decreased diastolic blood pressure. The latter two effects act to produce the typical bounding pulse seen in hyperthyroidism.
Development
T3 has profound effect upon the developing embryo and infants. It affects the lungs and influences the postnatal growth of the central nervous system. It stimulates the production of myelin, neurotransmitters, and axon growth. It is also important in the linear growth of bones.
T3 has profound effect upon the developing embryo and infants. It affects the lungs and influences the postnatal growth of the central nervous system. It stimulates the production of myelin, neurotransmitters, and axon growth. It is also important in the linear growth of bones.
Neurotransmitters
T3 may increase serotonin in the brain, particularly in the cerebral cortex, and down-regulate 5HT-2 receptors, based on studies in which T3 reversed learned helplessness in rats and physiological studies of the rat brain.
2. T4 (thyroxine)
T4 is involved in controlling the rate of metabolic processes in the body and influencing physical development. Administration of thyroxine has been shown to significantly increase the concentration of nerve growth factor in the brains of adult mice.
Thyroxine is a prohormone and a reservoir for the active thyroid hormone triiodothyronine (T3), which is about four times more potent. T4 is converted in the tissues by deiodinases, including thyroid hormone iodine peroxidase (TPO), to T3. The "D" isomer is called "Dextrothyroxine" and is used as a lipid modifying agent.
Reference:
http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/thyroid/physio.html
http://thyroxine.co.tv/
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From SUPER ENDOCRINOLOGIST
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