Hey Sasa. Hear anything from the doc about those thyroid test results? As far as the yerba mate goes, I know it's used in a lot of the "fat burners" on the market. Probably not good enough as a stand alone product. It's used in South America as a drink from what I've read, much like coffee or tea. Some info on it if you're interested:
Aside from providing a longer lasting and more tolerable energy than other caffeinated beverages like coffee, Mate also provides 196 active compounds, 24 vitamins and minerals, and 15 amino acids. Mate contains in the highest amounts chlorophyll, iron, trace minerals, vitamins A, E, and C as well as B-complex. Studies on PubMed have also shown extractions of Mate to have extremely power antioxidant effects. Furthermore, another study showed an herbal supplement including Mate (as well as guarana and Damiana) to be effective in aiding weight loss. Mate significantly delayed gastric emptying, reduced the time to perceived gastric fullness and induced significant weight loss over 45 days in overweight patients. On top of the few beneficial studies applicable to sports health, there is plenty of anecdotal evidence to suggest that Yerba Mate cleanses the blood, fights aging, stimulates the mind and the production of cortisone, tones the nervous system, and enhances the power of other herbs.
An average dose of Yerba Mate is usually 3 grams of unstandardized powder. If the mate is standardized, it is usually for caffeine content thus you would want to assess how much caffeine you want from the supplement. The side effects can generally be assumed similar to any caffeine ingestion but may be a bit milder than common caffeine sources such as coffee. Aside from superficial side effects, some studies have shown Yerba Mate to possibly be carcinogenic and to be a risk factor for cancer of the head and neck. Such risk is obviously dose dependent and probably only factor for those drinking Mate as a tea.