Thyroxine ( Levothyroxine , L-thyroxine , Tetraiodothyronine , T4 ) is the main thyroid hormone . Thyroxine is used in medicine to treat hypothyroidism (low levels of thyroid hormones), in bodybuilding, mainly as a means for losing weight, but also to compensate for hypothyroidism during the use of growth hormone.
What is the difference between T3 and T4
The thyroid gland mainly secretes T4 (thyroxine) – which is converted in peripheral tissues into the more active form of T3 (triiodothyronine) by the enzyme selenium-dependent monodeiodinase.
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 book on pharmacology 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.
In total we get:
- T3 is significantly more expensive
- T3 creates unwanted fluctuations in concentration
- Tissues with type 2 deiodinase additionally use triiodothyronine, which is formed from T4 inside the cell. This means that the intracellular level of T3 in these tissues will be lower, even if the concentration of thyroxine remains unchanged (and when taking a drug for burning fat, it will become lower than normal). From any source, you can find out that type 2 deiodinase is synthesized in adipose tissue.
- T4 has less muscle damaging effects reported by athletes.
- 25-100 mcg / day T3 is equivalent to ≈300 mcg / day T4
From the above arguments, it follows that thyroxine is preferable for burning fat, at least according to three criteria. In rare cases, T4 is not very effective because the level of its conversion to T3 decreases against the background of a low-carbohydrate diet.
The effects of thyroxine
- Boost your metabolism
- Increase of heat production
- Burning fat
- Stimulating effect on the CNS
- Appetite suppression
- Reduced need for sleep
- Improving physical performance
In terms of effectiveness, thyroxin surpasses most of the existing fat burners, including pharmacological ones.
Side effects of thyroxine and T3
- Tachycardia (palpitations), increased blood pressure – eliminated by beta-blockers
- Diarrhea – relieved by loperamide
- Muscle tremors
- Dry mouth
- Feeling hot
- Decreased thyroid function (occurs with long courses and very high doses of thyroxine, when using the recommended doses, the function is restored after 3-4 weeks)
- Allergic rash
A detailed description of the 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 use Thyroxin as a weight loss aid. Thyroxine has a powerful fat burning effect, increases calorie expenditure and speeds up metabolism. Its popularity has declined recently due to its negative effect on the heart, thyroxine has an adrenaline-like effect, making the heart beat faster, and at the same time it causes feelings of excitement and anxiety, which are not very well tolerated.
However, many side effects can be eliminated by combining thyroxine and beta-blockers. Beta-blockers inhibit the receptors through which thyroxine affects the heart, thus, they prevent the negative effect of thyroxine on the heart, normalize the rhythm and reduce the manifestation of some other side effects of thyroxine.
Many believe that thyroxine can irreversibly suppress the function of one’s own thyroid gland, however, studies have shown that even large doses of the drug in 3 weeks of administration reduce the secretion of their own hormones by only 20%, while after 4 weeks the secretion returned to normal.
Advantages of thyroxine: high availability and effectiveness. Disadvantages of thyroxine: There are quite a few side effects, but many of them can be prevented.
Exogenous thyroxine can cause artifactual thyrotoxicosis . In this case, in contrast to true hyperfunction of the thyroid gland, the level of thyroglobulin (TG) will be lowered.
How to take thyroxine: a weight loss course
- Start taking thyroxine with 50 mcg per day, 2 times a day (25 mcg each) in the first half of the day. In the morning, take 25 mg of metoprolol (a beta blocker that relieves congestion of the heart and palpitations) if the heart rate in the afternoon is above 70 beats. per minute at rest, then take another 25 mg of metoprolol.
- Gradually increase the dose to 150-300 mcg per day, 3 times a day until 18:00. Increase the daily dose of Metoprolol to 100 mg (2 times a day, 50 mg). The dosage of metoprolol is selected individually, so that the resting heart rate is 60-70 beats. per minute.
- Reduce thyroxine dose if severe side effects occur.
- Monitor your heart rate, if the resting heart rate is above 80 – increase the metoprolol dose by 25 mg, if the resting heart rate is below 60 beats per minute, reduce the metoprolol dose by 25 mg.
- Watch your blood pressure, it should not be higher than 140/90 mm Hg. Art. Metoprolol helps to lower blood pressure.
- Duration of the course is 4-7 weeks.
- Do not stop taking thyroxine abruptly: start reducing the dose 2 weeks before the end of the cycle, continue gradually reducing it until it is completely canceled.
- If you have diarrhea, include loperamide in the course, 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 per day, divided into 2-3 doses, after meals. Also, it will not be superfluous to improve the work of the heart with Riboxin. 2-4 tablets at a time, 2-3 times a day. Riboxin will improve the energy balance of the myocardium, and Asparkam will become a source of Potassium and Magnesium necessary to maintain a normal heart rate.
Course clenbuterol + thyroxine + yohimbine
This combination is used in fat burners from CYX3 AxioLabs , and is one of the most powerful. Significant savings can be made if the active ingredients are taken separately. The high efficiency of the complex is due to the fact that thyroxine (or triiodothyronine) is able not only to independently accelerate metabolism and start fat burning, but also to enhance the sensitivity of adrenergic receptors through which clenbuterol and yohimbine act.
The following combination of starting substances is taken as one unit (unit):
- Clenbuterol – 40 mcg
- Thyroxine – 25 mcg
- Yohimbine – 5 mg (available at sports nutrition stores)
The dosage is a multiple of the manufactured tablet forms of the mentioned drugs. Yohimbine can be excluded from the complex if you do not have the opportunity to purchase it, while the dosage 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 unit. in the morning, 1 unit. after lunch
- day 10-12: 1.5 units
- day 13-15: 1 unit
- day 16-19: 0.5 units
- day 20-21: 0, 25 units
Only 23.5 units.
In the next three weeks, it is recommended to give the body a rest, after which the course can be repeated. All substances are recommended to be taken 30 minutes before breakfast with plain water.
In the event of a febrile condition, it is recommended to take 1-2 mg of ketotifen in the afternoon. To protect the heart and reduce the heart rate, it is necessary to use beta-blockers (metoprolol at a dose of 50 mg 2 times a day).