T3 for weight loss
Pro Research Analysisby 
Searched over 200M research papers
Consensus Meter
The Role of Triiodothyronine (T3) in Weight Loss
Introduction to T3 and Weight Loss
Triiodothyronine (T3) is a thyroid hormone known to play a significant role in regulating metabolism and energy expenditure. Its potential use in weight loss therapies has been explored in various studies, with mixed results regarding its efficacy and safety.
T3 and Energy Expenditure
Several studies have demonstrated that T3 can influence energy expenditure and metabolic rate. For instance, T3 repletion in weight-reduced individuals has been shown to reverse the increased skeletal muscle work efficiency and changes in myosin heavy chain isoforms that occur with weight loss, similar to the effects of leptin repletion. Additionally, T3 therapy has been found to increase basal metabolic rate and protein turnover, although the increases were not statistically significant.
T3 and Weight Loss Efficacy
The effectiveness of T3 in promoting weight loss has been observed in multiple studies. In a double-blind trial, obese patients on a very-low-calorie diet who received T3 experienced significantly greater weight loss compared to those on a placebo. Similarly, another study found that T3 treatment increased the rate of weight loss in obese patients, although this was primarily at the expense of lean body mass rather than fat.
Impact on Thyroid Hormone Homeostasis
Moderate weight loss has been shown to affect thyroid hormone homeostasis, with a significant decrease in T3 levels observed in individuals who lost more than 5% of their body weight. This suggests that weight loss can lead to a reduction in the peripheral conversion of thyroxine (T4) to T3, impacting overall thyroid hormone balance.
T3 and Resting Metabolic Rate
The decrease in resting metabolic rate (RMR) during rapid weight loss can be partially reversed by low-dose thyroid hormone treatment. In one study, T3 and T4 administration increased RMR to near baseline levels in obese subjects on a very low energy diet, although the increase was not complete. This indicates that reduced serum T3 concentrations contribute to the decrease in RMR during weight loss.
Risks and Considerations
Despite its potential benefits, the use of T3 in weight loss therapy is not without risks. Prolonged T3 treatment can result in significant losses of lean tissue, as well as potential heart rhythm disturbances due to its effects on the thyroid hormone receptor alpha (TRα) . Additionally, a systematic review concluded that the available data are inconclusive regarding the effectiveness of thyroid hormone therapy in treating obesity, and such therapy may induce subclinical hyperthyroidism.
Conclusion
While T3 has shown promise in increasing metabolic rate and promoting weight loss, its use must be carefully considered due to potential adverse effects and the loss of lean body mass. Further research is needed to fully understand the role of T3 in weight loss and to develop safe and effective therapeutic strategies.
Sources and full results
Most relevant research papers on this topic