Levothyroxine sodium is the first in the United States commercial synthetic drug for the thyroid gland treatment, which was firstly introduced to the market in 1955 under the name Synthroid from Flint Laboratories. The drug has a long history of therapeutic use in the U.S. and internationally, and has been the most widely used drug of hypothyroidism treatment for decades. The figures show that the brand Synthroid provided 85% of levothyroxine total sales, and the annual income from the drug sale is $600 million.

Chemical structure

Thyroxine is amino acid tyrosine derivative. The hormone contains four iodine atoms in its contents. Iodine comes into the thyroid gland with blood. The compounds of this trace element are essential in the human diet. Lack of iodides in food and water can provoke endemic diseases (primarily, diffuse and nodular goiter).

The molecular weight of thyroxine - 777 D. Iodine atoms account for about 83% of the weight. Chemical formula T4: 3,5,3,5-tetraiodothyronine.

Hormone synthesis takes place in the follicles of the thyroid gland. T4 hormone is produced in the protein thyroglobulin. First, a tyrosine joins two atoms of iodine. Then it connects the two remains of the resulting diiodtirozina molecule. Alanine is cleaved from the compound.



  • Substance activity: 6 hours
  • Classification: Synthetic thyroid hormone
  • Method of application: tablets
  • Dosage: Men 8-12 units per day
  • Acne: Yes
  • Water retention: not significant
  • High blood pressure: there are contraindications
  • Hepatotoxicity: not allowed to take with abnormal liver function
  • Detection time: 6-8 days




  • Metabolism acceleration
  • Increased heat production
  • Fat burning
  • The stimulating effect of the central nervous system
  • Appetite suppression
  • Reduced need in sleep
  • Increase physical performance


According to its effectiveness, thyroxine is superior to most of the existing fat burners, including pharmacological.

Side effects


  • Tachycardia (palpitations), increased blood pressure - is eliminated by beta-blockers
  • Osteoporosis
  • Diarrhea – is eliminated by loperamide
  • Excitement
  • Insomnia
  • Muscle tremors
  • Dry mouth
  • Sweating
  • Heat feeling 
  • Decrease thyroid function (it occurs during long courses and very high doses of thyroxine taking; if recommended doses are used, the function is restored in 3-4 weeks)
  • Allergic rash


Detailed description of the side effects can be found in the instructions. It is also necessary to consult a specialist to identify contraindications.

However, many side effects can be avoided if you combine thyroxine and beta-blockers. Beta-blockers inhibit the receptors through which the thyroxine affects the heart, thus, they prevent the thyroxin negative effect on heart, normalize rhythm and reduce expression of certain other thyroxine side effects.

Dosages and Uses

Dosage: 4-8 units / day for amateur athletes, 8-12 units / day for professionals.

Dosage frequency: every day

Many women and bodybuilders use thyroxine to lose weight. Thyroxine has a powerful fat-burning effects, increases the calorie consumption and metabolism.

Cycles (Courses)


  • Start thyroxine taking with 50 micrograms per day, 2 times a day (25 mg) during the first half of the day. In the morning take 25 mg of metoprolol (a beta-blocker, which eliminates the heart overloading and heart rate), if the pulse rate is above 70 bpm per minute during the rest in the afternoon, take another portion ( 25 mg) of metoprolol.
  • Gradually increase the dose to 150-300 mg per day, 3 times a day until 18:00. Increase daily dose of metoprolol to 100 mg (50 mg 2 times a day). Metoprolol dosage is adjusted individually so that the pulse rate was 60-70 bpm per minute during rest.
  • Reduce the thyroxine dose, if any significant side effects appeared.
  • Keep an eye on the heart rate, when the heart rate is above 80 during rest - increase the dose of metoprolol to 25 mg, if the heart rate is below 60 beats per minute during the rest - reduce the dose of metoprolol to 25 mg.
  • Keep an eye on your blood pressure, it should not be higher than 140/90 mm m. c. Metoprolol can reduce blood pressure.
  • The duration of the course is 4-7 weeks.
  • Do not stop taking thyroxine sharply; start to lower the dose 2 weeks before the end of the cycle, continue gradually decline it till complete withdrawal.
  • If you have a diarrhea - include loperamide (1-2 capsules per day) in the course.
  • The minimal break after the course end is 3-4 weeks.


Combined courses

Course clenbuterol + thyroxine + yohimbine

This combination is used in fat burners CYX3 from AxioLabs, and is one of the most powerful. You can save considerably if you take active ingredients separately. The high efficiency of the complex is possible because of the fact that thyroxin (or triiodothyronine) can not only accelerate metabolism and start fat burning, but also enhance the sensitivity of adrenergic receptors, through which Clenbuterol and yohimbine take effect.

The following combination of starting materials is taken as UI:


  • Clenbuterol - 40 mcg
  • thyroxine - 25 mkg
  • Yohimbine - 5 mg (available in stores of sports nutrition)


Yohimbine can be excluded from the complex if you can not buy it, and the dosage and taking scheme of the remaining 2 drugs be the same.

Recommended course


  • day 1-3: 1 UI
  • day 4-6: 1,5 UI
  • day 7-9: 1 UI in the morning, 1 UI in the afternoon
  • day 10-12: 1,5 UI
  • day 13-15: 1 UI
  • day 16-19: 0,5 UI
  • day 20-21: 0, 25 UI

Next three weeks it is recommended to give the body a rest, after which the course can be repeated. All substances are recommended to take 30 minutes before breakfast and wash down it with plain amount of water.


In case of fever it is recommended to take 1-2 mg of ketotifen in the afternoon. Beta blockers (50 mg of metoprolol 2 times a day) must be used to protect the heart and to reduce the heart rate.