Triiodothyronine T3 is not an anabolic steroid, but it plays a similar role to anabolic steroids to some extent. Although it is a drug used to treat hypothyroidism, but as a hormone (thyroid hormone), bodybuilders use it in the process, there will be corresponding side effects.
Thyroid axis inhibition
The first is the inhibition similar to that of anabolic steroids. Exogenous T3 inhibits pituitary secretion of thyrotropin hormone (TSH) and thyroid secretion of thyroid hormone through negative feedback mechanism, and long-term inhibition of thyroid axis may lead to thyroid dysfunction. Heavy use of exogenous T3 may lead to hyperthyroidism, especially an overactive thyroid with symptoms such as rapid heartbeat, anxiety, sweating, weight loss, and fatigue.
Bone loss
Triiodothyronine T3 promotes skeletal muscle use of minerals such as calcium and phosphorus, which helps bone growth and development. Long-term use of it may lead to decreased bone density and an increased risk of osteoporosis and fractures.
Metabolic disorder
T3 causes the metabolism to accelerate, resulting in rapid weight loss, increased heat production, and excessive sweating. If you do not exercise, the breakdown of muscle proteins will occur, resulting in muscle loss.
Heart problem
T3 also has an impact on the cardiovascular system, leading to increased heart rate, palpitations, high blood pressure and an increased risk of arrhythmia. These effects can be especially dangerous for people who already have heart disease.
Sleep problem
T3 increases the basal metabolism, which can cause problems with excitement, insomnia, light sleep and more.
Psychological influence
T3 use can also affect mental health. Some people may feel anxious, irritable, mood swings, etc. These psychological side effects may sometimes affect normal work and life.
The thyroid hormone T3 is a powerful hormone that plays an important role throughout the body, and care should be taken to test the level of thyroid hormone in the body at any time during the use of T3. At the same time, do not overuse it for a long time to avoid serious side effects.

When bodybuilders use Triiodothyronine T3, it is usually used during the cutting phase, which increases the basal metabolism, reduces fat and prevents muscle loss. Previously, T3 increased the basal metabolism and reduced fat, and today we will focus on how it can prevent muscle loss.
In the cutting stage, it is mainly necessary to lose the fat stored during weight gain, obtain a more linear muscle appearance, and retain as much muscle as possible in this process to prevent the loss of muscle. Triiodothyronine T3 just happens to reduce fat and prevent muscle loss.
In the process of Cutting, bodybuilders need to control their diet while increasing their exercise. In this process, the energy intake is often less than the energy consumed during exercise, leaving the body in a hungry and low energy state. During this process, the body preferentially breaks down muscles for energy.
At the same time, in the previous article about rT3, we know that the amount of rT3 produced by the body increases when the body is hungry or in a low energy state. rT3 further lowers the body's basal metabolism and begins to conserve fat. At the same time, rT3 competes with T3 for receptors, making T3 ineffective.
This is very bad for fat loss and muscle preservation in the cutting stage.
Skeletal muscle is a direct target of the thyroid hormone Triiodothyronine T3, which regulates stem cell proliferation and differentiation, and muscle fiber metabolism. In the experiment, T3 to prevent hunger mediated metabolic changes, offset the hunger caused by muscle loss, which retained the muscle quality.
Instead of preventing muscle loss by simply increasing anabolism, and without altering normal protease-mediated catabolism, T3 directly regulates muscle metabolism to counteract muscle loss.
How to prevent muscle loss in the Cutting stage or PCT stage is a very important problem, which is to some extent more difficult than acquiring muscle. The perfect muscle that Bodybuilders pursue is definitely not that bloated look, and cutting is a very important lesson for bodybuilders. Losing fat and preventing muscle loss during the cutting phase, Triiodothyronine T3 does it.

The thyroid hormone T3(triiodothyronine) improves overall basal metabolism and heat production, increasing the body's oxygen and energy expenditure. How does T3 improve overall basal metabolism?
What is basal metabolism?
Basal metabolism, also known as basal metabolic rate (BMR), is the minimum caloric requirement required to maintain a resting individual's life. It represents the energy expenditure necessary to maintain basic physiological processes such as respiration, circulation, cell maintenance and the maintenance of body temperature.
Why improve your basal metabolism?
In general, people with a high basal metabolic rate tend to burn more calories when at rest, which helps with easier weight control and helps prevent weight gain.
People with a lot of muscle mass tend to have a higher basal metabolic rate because muscle requires more energy to maintain compared to fat.
How does T3 improve basal metabolism?
The thyroid hormone T3 acts on most tissues in the body, enhancing their function and metabolism.
Acts on proteins: T3 affects cell metabolism by affecting gene expression and protein synthesis. It regulates the metabolism of carbohydrates, proteins and promotes the utilization of nutrients to produce energy.
Increased glucose uptake: T3 enhances glucose metabolism and promotes glucose transport to cells, primarily in muscle and adipose tissue. It enhances the activity of glucose transporters and promotes the uptake of glucose from the blood into cells.
Enhances glycolysis: T3 increases the activity of enzymes involved in glycolysis, resulting in an increase in energy (in the form of ATP) produced by glucose.
Increased glycogen breakdown: Glycogen is the glucose stored in the liver and muscles. T3 promotes the release of this glucose into the blood, providing a direct source of energy.
Increased lipid metabolism: T3 stimulates cholesterol breakdown and increases the number of LDL receptors, thereby increasing the rate of fat decomposition.

There are two sources of T3 in the body, one is directly secreted by the thyroid gland, which accounts for 20% of the total T3 in the body. The other is converted from T4, which makes up 80% of the body's total T3.
The thyroid gland directly secretes T3
The production and release of thyroid hormones, T4 and T3 are controlled by a feedback loop on the hypothalamic-pituitary-thyroid axis. T4 and T3 are the main thyroid hormones.
When the body detects low levels of thyroid hormones (T4 and T3), the pituitary gland releases thyrotropin to stimulate the thyroid gland to produce more thyroid hormone. The amount of thyroid-stimulating releasing hormone produced by living organisms depends on the body's need for thyroid hormone. Once the levels of thyroid hormones (T4 and T3) in the blood reach normal levels, the pituitary gland stops releasing thyroid-stimulating releasing hormone. In this way, the system enables the body to maintain constant levels of thyroid hormones (T4 and T3).
In this process, the thyroid hormones T3 and T4 are present at the same time, so under what circumstances is T3 produced, and under what circumstances is T4 produced?
The process of thyroid hormone synthesis can be summarized as four steps: "polyiodide - activation - iodide - condensation". T3 and T4 are formed in the condensation of the last step. In the process of iodination, the ammonia on the phenyl ring of tyrosine is replaced by activated iodine catalyzed by TPO(thyroid peroxidase) to form MIT(monoiodotyrosine) or DIT(diiodotyrosine). Then, in the process of condensation, catalyzed by TPO, one MIT and one DIT condense to produce T3 and a very small amount of rT3, and two Dits condense to produce T4.
This part of T3 is directly generated and accounts for about 20% of the total T3. The other 80% of T3 that the body needs is converted from T4.
How does T4 turn into T3?
T4 is produced by a deiodination reaction, in which an iodine atom is removed by metabolic enzymes in the peripheral tissues to form T3. There are three types of deiodinases involved in this process, type I, type II and type III deiodinases. Type I is found mainly in the liver, kidneys, thyroid, and pituitary gland, type II in the central nervous system, pituitary gland, brown adipose tissue, and cardiovascular tissues, and type III in the placenta, CNS, and hemangiomas. Type III deiodinase mainly converts T4 to rT3, which, unlike T3, is inactive and counteracts some of the effects of T3.
The conversion efficiency of T4 to T3 is different, and the conversion efficiency of young people is higher than that of old people.