Drug Class: Synthetic Thyroid Hormone. (Oral)
Average Reported Dosage: 100-400 MCG daily.
Noted Comments: Significant suppression of thyroid function during use. Synthroid is a man-made synthetically manufactured version of T-4/L-thyroxine. The average person produces about 76 MCG/d of T-4/L-thyroxine which is then converted by the liver into the more active T-3/L-triiodothyronine. This is true of the oral T-4/L-thyroxine medications as well. The average conversion rate of T-4 to T-3 is about 30-33%/ MCG. Since the conversion of T-4 to T-3 is dependent upon adequate levels of since and selenium, athletes commonly increase daily intake of these minerals during synthetic T-4/L-thyroxine use. As is the case with all thyroid hormone drug use, most athletes were noted as wiser to begin at a lower dosage of 100 MCG/d and slowly progress to their chosen dosage. Daily dosages of T-4/L-thyroxine that exceed 400 MCG will not increase metabolic rate beyond what is realized at 400 + MCG/d. Dosages that were increased too rapidly or that were too high commonly resulted in diarrhea, excessive sweating, rapid heart beat, nausea, vomiting, insomnia and trembling. T-4 drugs suppress endogenous thyroid hormone production significantly. After discontinuance, most athletes experienced a metabolic lag period of 3-15 days before thyroid function rebound occurred. Interesting fact is that most monitored athletes experienced a 120-130 % increase in endogenous thyroid hormones at that point. And some maintain that level permanently. *See guggulsterones for other possibilities.