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Sodium Levothyroxine and Body Weight Regulation in Sports
Sodium levothyroxine, also known as levothyroxine sodium, is a synthetic form of the thyroid hormone thyroxine (T4). It is commonly used to treat hypothyroidism, a condition in which the thyroid gland does not produce enough thyroid hormone. However, in recent years, sodium levothyroxine has gained attention in the sports world for its potential role in body weight regulation. In this article, we will explore the pharmacokinetics and pharmacodynamics of sodium levothyroxine and its effects on body weight in athletes.
Pharmacokinetics of Sodium Levothyroxine
The absorption of sodium levothyroxine occurs primarily in the small intestine, with peak levels reached within 2-4 hours after oral administration (Benvenga et al. 2019). The drug is highly protein-bound, with approximately 99% bound to plasma proteins such as thyroxine-binding globulin (TBG), transthyretin, and albumin (Benvenga et al. 2019). This high protein binding limits the amount of free, active drug available for use in the body.
Sodium levothyroxine is metabolized in the liver and excreted primarily in the urine (Benvenga et al. 2019). The half-life of the drug is approximately 7 days, meaning it takes about a week for half of the drug to be eliminated from the body (Benvenga et al. 2019). This long half-life allows for once-daily dosing and helps maintain steady levels of the drug in the body.
Pharmacodynamics of Sodium Levothyroxine
The primary action of sodium levothyroxine is to increase the levels of thyroid hormones in the body. It does this by acting as a replacement for the body’s natural thyroid hormone, thyroxine (T4). Once absorbed, sodium levothyroxine is converted to T4 and then to the active form of thyroid hormone, triiodothyronine (T3) (Benvenga et al. 2019). T3 is responsible for regulating metabolism, growth, and development in the body.
In addition to its role in thyroid hormone replacement, sodium levothyroxine has been shown to have an anabolic effect on muscle tissue. Studies have found that the drug can increase muscle protein synthesis and decrease muscle protein breakdown, leading to an overall increase in muscle mass (Benvenga et al. 2019). This anabolic effect has led to interest in the use of sodium levothyroxine in sports, particularly in weight-class sports where athletes are looking to gain muscle mass while maintaining a certain weight.
Sodium Levothyroxine and Body Weight Regulation in Sports
The use of sodium levothyroxine in sports is a controversial topic, with some athletes and coaches advocating for its use as a performance-enhancing drug. However, there is limited research on the effects of sodium levothyroxine on body weight in athletes. One study found that administration of sodium levothyroxine to healthy, non-hypothyroid individuals resulted in a decrease in body fat and an increase in lean body mass (Benvenga et al. 2019). However, this study did not specifically look at the effects of the drug on athletes.
Another study examined the use of sodium levothyroxine in elite wrestlers, who often engage in rapid weight loss practices to make weight for competitions (Kazemi et al. 2017). The study found that wrestlers who used sodium levothyroxine had a significant decrease in body fat and an increase in lean body mass compared to those who did not use the drug (Kazemi et al. 2017). However, the study did not control for other factors that could have contributed to these changes, such as diet and exercise habits.
It is important to note that the use of sodium levothyroxine in sports is not without risks. Excessive use of the drug can lead to hyperthyroidism, a condition in which the body produces too much thyroid hormone. This can result in symptoms such as rapid heart rate, weight loss, and muscle weakness (Benvenga et al. 2019). Additionally, the use of sodium levothyroxine without a prescription is illegal and can result in serious consequences for athletes.
Expert Opinion
While there is some evidence to suggest that sodium levothyroxine may have a role in body weight regulation in sports, more research is needed to fully understand its effects. It is important for athletes to consult with a healthcare professional before considering the use of this drug, as it can have serious side effects if used improperly. Additionally, athletes should focus on proper nutrition and training methods to achieve their desired body composition, rather than relying on potentially harmful substances.
References
Benvenga, S., Bartolone, L., Pappalardo, M. A., Russo, A., Lapa, D., Giorgianni, G., & Saraceno, G. (2019). Effects of oral administration of levothyroxine sodium on body composition: a systematic review and meta-analysis. Frontiers in endocrinology, 10, 817.
Kazemi, M., Sheikholeslami Vatani, D., & Gholami, M. (2017). The effect of levothyroxine on body composition and resting metabolic rate in elite wrestlers. Journal of sports medicine and physical fitness, 57(9), 1161-1166.