【商品名称】 三碘甲状腺氨酸钠、碘赛罗宁 T3、Liothyronine Triiodothyronin
【英文名称】 Liothyronine Sodium
T3 (Liothyronine sodium)
Liothyronine sodium is the L-isomer of triiodothyronine (T3), a form of thyroid hormone. T3 increases the basal metabolic rate and, thus, increases the body's oxygen and energy consumption. The basal metabolic rate is the minimal caloric requirement needed to sustain life in a resting individual. T3 acts on the majority of tissues within the body.
The thyroid gland releases greater amounts of T4 than T3, so plasma concentrations of T4 are 40-fold higher than those of T3. Most of the circulating T3 is formed peripherally by deiodination of T4 (85%), a process that involves the removal of iodine from carbon 5 on the outer ring of T4. Thus, T4 acts as prohormone for T3.
The T3 (and T4) bind to nuclear receptors, thyroid receptors. However, T3 (and T4) are not very lipophilic and, as a result, are unable to pass through the phospholipid bilayers. They, therefore, have specific transport proteins on the cell membranes of the effector organs that allow the T3 and T4 to pass into the cells. The thyroid receptors bind to response elements in gene promoters, thus enabling them to activate or inhibit transcription. The sensitivity of a tissue to T3 is modulated through the thyroid receptors.
T3 and T4 are carried in the blood bound to plasma proteins. This has the effect of increasing the half-life of the hormone and decreasing the rate at which it is taken up by peripheral tissues. There are three main proteins that the two hormones are bound to: thyronine-binding globulin (TBG), a gylcoprotein that has a higher affinity for T4 than for T3; transthyretin, which has a higher affinity for T3 than for T4. Both hormones bind with a low affinity to serum albumin, but, due to the large availability of albumin, it has a high capacity.
- 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. It also potentiates the effects of insulin, which have opposing effects.
- Lipids -
T3 stimulates the breakdown of cholesterol and increases the number of LDL receptors, therefore increasing the rate of lipolysis.
T3 also affects the cardiovascular system. It increases the cardiac output by increasing the heart rate and force of contraction. 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.
T3 also 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 reduce serotonin in the brain, based on a study in which T3 reversed learned helplessness in rats.
Cytomel - Synthetic Analogue of the Thyroid Hormone T3
The drugs Cytomel is a thyroid hormone.
Cytomel - Synthetic Analogue of the Thyroid Hormone T3
Cytomel contains synthetically manufactured hormone - liothyronine sodium. It is the exact equivalent to a natural thyroid hormone and causes the same processes in human organism as the natural one. Cytomel helps sufficiently in treatment of thyroid insufficiency (hypothyroidism) and such symptoms like obesity, fatigue and metabolic disorders.
However, the drug is in a big demand among bodybuilders. By taking the medicine, they stimulate the metabolism, since the drug causes a faster conversion of proteins, fats and carbohydrates.
How Cytomel should be taken?
It is very important to stick to the exact dosage since the drug is very effective and strong one. In the beginning Cytomel should be administered in a low dosage. Taking a big dose is very dangerous. The dose can be increase slowly after several days of administration.
The majority of athletes start taking Cytomel with 25mg dose per day and increase it every 3-4 days adding one more tablet.
Taking a dose of 100 mg a day is not recommended! It is not recommended that the daily dose be taken all at once but broken down into three smaller individual doses so that they become more effective. It is also important that Cytomel not be taken for more than six weeks. At least two months of abstinence from the drug needs to follow. Those who take high dosages of Cytomel over a long period of time are at risk of developing a chronic thyroid insufficiency.
Cytomel possible side effects
Possible side effects such as medication are described in the package insert by the German pharmaceutical group Hoechst AG for their compound Thybon: "exceeding the individual limits of compatibility for liothyronine or taking an overdose, especially, if the dose is increased too quickly at the beginning of the treatment, can cause the following clinical symptoms for a thyroid hyperfunction): heart palpitation, trembling, irregular heartbeat, heart oppression, agitation, shortness of breath, excretion of sugar through the urine, excessive perspiration, diarrhea, weight loss, psychic disorders, etc., as well as symptoms of hypersensitivity." Our experience is that most symptoms consist of trembling of hands, nausea, headaches, high perspiration, and increased heartbeat. These negative side effects can often be eliminated by temporarily reducing the daily dosage.
Caution, however is advised when taking Cytomel since, especially in the beginning, the effect can be quick and sometimes drastic. Athletes do not use the injectable version of L-T3, this is normally used as "emergency therapy for thyrotoxic coma." Those who use Cytomel over several weeks will experience a decrease in muscle mass. This can be avoided or delayed by simultaneously taking steroids. For the most part, since Cytomel also metabolizes protein, the athlete must eat a diet rich in protein.
5mcg錠 ： 100錠（バラ）、1,000錠（10錠×100）
25mcg錠 ： 100錠（バラ）