Thyroxine (Levothyroxine, L-Tyroxine, Tetraiodothyronine, T4) is the main thyroid hormone. Thyroxine is used in medicine to treat hypothyroidism (reduced levels of thyroid hormones), in bodybuilding primarily as a means for weight loss, but also to compensate for hypothyroidism during the use of growth hormone.
Triiodothyronine (T3) or liothyronine – often used for weight loss instead of thyroxine, they are almost identical in mechanism of action. T3, unlike T4, has a more active effect on the biochemical pathways of protein catabolism. When both drugs are dosed to provide the same fat loss, T3 “burns” much more muscle than T4.
What is the difference between T3 and T4
The thyroid gland secretes mainly T4 (thyroxine) – which in peripheral tissues is converted to the more active form of T3 (triiodothyronine) by the enzyme selenium-dependent monodeiodinase. Thus, T4 can be considered a prohormone.
On many resources, triiodothyronine is considered the best choice, but scientific evidence suggests otherwise. Quote from Goodman’s Clinical Pharmacology, latest 12th edition from 2010, the most authoritative pharmacology book in the world:
Liothyronine is less desirable for chronic replacement therapy due to the requirement for more frequent dosing (plasma t1/2 = 0.75 days), higher cost, and transient elevations of serum T3 concentrations above the normal range. In addition, organs that express the type 2 deiodinase use the locally generated T3 in addition to plasma T3, and hence there is theoretical concern that these organs will not maintain physiological intracellular T3 levels in the absence of plasma T4.
- T3 is noticeably more expensive
- T3 creates undesirable concentration fluctuations
- Tissues with deiodinase type 2 use additionally triiodothyronine, which is formed from T4 inside the cell. This means that intracellular T3 levels in these tissues will be lower if even the concentration of thyroxine remains unchanged (and it will become lower than normal when taking a fat burning drug). You can learn from any source that type 2 deiodinase is synthesized in adipose tissue.
- Athletes report that T4 has less of a damaging effect on muscle.
- 25-100 µg/day of T3 is equivalent to ≈300 µg/day of T4
From the arguments presented above, it follows that thyroxine is preferable for fat burning by at least three criteria. In rare cases, T4 has a low efficacy, because its conversion to T3 is reduced on a low-carbohydrate diet.
Effects of thyroxine
- Metabolic acceleration
- Strengthening heat production
- Fat burning
- CNS stimulating effect
- Appetite inhibition
- Decrease in the need for sleep
- Increases physical performance
Thyroxine is superior to most existing fat burners, including pharmacological ones.
Side effects of thyroxine and T3
- Tachycardia (heart palpitations), increased blood pressure – can be treated with beta-adrenoblockers
- Diarrhea – resolved with loperamide
- Muscle tremor
- Dry mouth
- Feeling of heat
- Decreased thyroid function (occurs with long courses and very high doses of thyroxine; if recommended doses are used, function is restored after 3-4 weeks).
- Allergic rash
A detailed description of side effects can be found in the instructions. It is also necessary to consult a specialist to identify contraindications.
Thyroxine for weight loss
Many women and bodybuilders resort to using Thyroxine as a weight loss aid. Thyroxine has a powerful fat-burning effect, increases calorie expenditure and speeds up the metabolism. Its popularity has declined recently due to its negative effects on the heart; thyroxine has an adrenaline-like effect, causing the heart to beat faster, and along with this it causes feelings of anxiety and worry, which are not well tolerated. However, many of the side effects can be eliminated by combining thyroxine and beta-blockers. Beta-blockers inhibit the receptors through which thyroxine affects the heart, so they prevent the negative effects of thyroxine on the heart, normalize rhythm, and reduce the appearance of some of the other side effects of thyroxine.
Many believe that thyroxine can irreversibly suppress the function of their own thyroid gland, but studies have shown that even large doses of the drug in 3 weeks of taking it reduce the secretion of their own hormones by only 20%, with the secretion returning to normal after 4 weeks.
Advantages of thyroxine: high availability and effectiveness. Disadvantages of thyroxine: quite a large number of side effects, but many of them are preventable.
Exogenous thyroxine can cause artificial thyrotoxicosis. In this case, unlike true thyroid hyperfunction, thyroglobulin (TG) levels will be lowered.
How to Take Thyroxine: A Course for Weight Loss
- Start taking thyroxine at 50 mcg per day, twice a day (25 mcg each) in the first half of the day. In the morning, take 25 mg of metoprolol (a beta-blocker that eliminates heart overload and palpitations); if your pulse rate in the afternoon is above 70 bpm at rest, take another 25 mg of metoprolol.
- Gradually increase the dose to 150-300 mcg daily, 3 times a day until 6 p.m. Increase the daily dose of metoprolol to 100 mg (50 mg twice daily). Dose metoprolol individually, so that your resting pulse rate is 60-70 bpm.
- Reduce the thyroxine dose if you experience significant side effects.
- Monitor your pulse rate; if your resting heart rate is above 80, increase the metoprolol dose by 25 mg; if your resting pulse rate is below 60 beats per minute, reduce the metoprolol dose by 25 mg.
- Monitor your blood pressure; it should not be higher than 140/90 mm Hg. Metoprololol allows you to lower the blood pressure.
- The course duration is 4-7 weeks.
- Do not stop taking thyroxine abruptly: start reducing the dose 2 weeks before the end of the cycle, continue the gradual reduction until complete withdrawal.
- If you have diarrhea, include loperamide in the course of 1-2 capsules per day.
- The minimum break after the end of the course is 3-4 weeks.
- If there is heaviness in the heart area, it is better to add Asparkam in addition to Metoprolol. 4-6 tablets a day, divided into 2-3 intakes, after meals. It is also absolutely not superfluous to improve heart function with the drug Riboxin. 2-4 tablets at a time, 2-3 times a day. Riboxin will improve myocardial energy balance, and Asparkam will be a source of Potassium and Magnesium necessary to maintain a normal heart rhythm.
A course of clenbuterol + thyroxine + yohimbine
This combination is used in the fat burner CYX3 from AxioLabs and is one of the most powerful. You can save significantly if you take the active ingredients separately. The high efficiency of the complex is due to the fact that thyroxine (or triiodothyronine) is not only able to speed up the metabolism and start burning fat, but also to increase the sensitivity of adrenoreceptors, through which clenbuterol and yohimbine act.
One unit is based on the following combination of starting ingredients:
- Clenbuterol – 40 µg
- Thyroxine – 25 mg
- Yohimbine – 5 mg (available in sports nutrition stores)
The dosage is a multiple of the manufactured tablet forms of the above drugs. You can exclude yohimbine from the complex, if you do not have the opportunity to buy it, and the dosages and regimen of the remaining 2 drugs will be the same.
- day 1-3: 1 unit.
- day 4-6: 1.5 units.
- day 7-9: 1 iu in the morning, 1 iu in the afternoon
- day 10-12: 1.5 units.
- days 13-15: 1 iu.
- day 16-19: 0.5 units.
- day 20-21: 0.25 units.
Total 23.5 units.
In the next three weeks it is recommended to give the body a rest, after which the course can be repeated. It is recommended that all substances be taken 30 minutes before breakfast, with plain water.
In case of a febrile state, it is recommended to take 1-2 mg of ketotifen in the afternoon. Beta-adrenoblockers (metoprolol in a dose of 50 mg 2 times a day) should be used to protect the heart and reduce heart rate.
Anabolic drugs should only be used as prescribed by a physician and are contraindicated in children. The information provided does not encourage the use or distribution of potent substances and is intended solely to reduce the risk of complications and side effects.