Guggulsterone are an extract of the herb Commiphora Mukul, clinically proven to restore lagging metabolic rate caused by dietary calorie deficiency such as during diet phases. Ayurvedic medicine has utilized the unprocessed herb for centuries to treat energy deficiencies related ailments.
Guggulsterones Z and E seem to have the greatest effect upon stimulation of thyroid hormone, though other substrates of the herb commiphora mukul may effect different metabolic factors as well. Thus far, research suggests this is a result of guggulsterones Z & E stimulation of TSH (Thyroid-Stimulating-Hormone) production. This results in an increase in Thyroid gland T-4 production and subsequent liver conversion to the more active T-3 hormone.
Guggulsterones can be very beneficial to dieting athletes. When calorie intake is decreased, the body naturally decreases metabolic rate or calorie expenditure. This is why dieters often hit a fat loss wall after 2-4 weeks. Since TSH production begins the entire thyroid hormone cascade, guggulsterones can be very helpful at restoring "normal" metabolic rate at this point. It should be noted that guggulsterones do not inhibit normal thyroid activity or induce a negative feed-back loop. It is very unlikely that the use of this extract will lead to above normal accepted TSH, T-4, T-3 reference range production.
Other benefits of guggulsterone supplementation include reduced blood cholesterol and triglyceride levels, increased fat oxidation (fat burning), increased energy, and better post-training recovery during diet restriction phases. Reduced acne has been noted.
Please note that other diet defiencies can lead to reduced metabolic rate including phosphates, niacin, selenium, and magnesium among others, such as Zinc.
Some athletes used guggulsterones to regenerate thyroid function after discontinuance of synthetic T-3/T-4 protocols. Those who thought ahead, utilized guggulsterones " synthetic T-3/T-4 thyroid hormone use to prevent thyroid function suppression even temporarily. This usually was initiated 10-14 days prior to synthetic thyroid administration discontinuance. Coleus Forskohlii, the amino acid tyrosine, and iodine also had a noted great deal of value for this purpose.
L. Rea (2002) - Chemical Muscle Enhancement Bodybuilders Desk Reference