Apart from being known as an aphrodisiac there isn't anything in it that is going to be harmful to you or your thyroid condition. Just remember to take it well away in hours from other medications.
Not true AT ALL.
maca acts on the pituitary gland and hypothalamus, so it may rise the level of your TSH (thyroid stimulating hormone) and have a possible effect on the thyroid cancer cell turnover. However, I have not found any studies confirming its effect(s). But I would like to know, for I have thyroid cancer and suffering from menopausal problems.