The thyroid hormone, thyroxine (T4) is a tyrosine-based hormone which is produced by the thyroid gland. Synthetic versions of this hormone are used to make up for a lack of naturally produced thyroxine and increase the rate of metabolism. Artificially made thyroid hormone improves the symptoms of hypothyroidism (underactive thyroid) and speeds the rate of metabolism in those who suffer from the disease. Thyroid hormones may also be used to treat goiter (enlarged thyroid gland) and certain types of thyroid cancer.
T4 must be used in much higher doses to be as effective as T3. Subjects found they needed to use a dosage of 300 mcg/day to achieve the same results as 25-100 mcg/day of T3 (Cytomel).
How to use:
Most bodybuilders use use GH for precontest dieting, and T4 has found a bit of a niche for those using GH and dieting. At this point, whether on a diet or not, T4 has become a much sought after drug for use with cutting cycles which include Growth hormone. I have even received a phone call from doctors and Hormone Replacement Clinics, who wanted more practical information on the use of GH + T4.So, at this point, I think that most of the people in the bodybuilding world who are using T4 are using it along with their Growth Hormone for the most part.