Herbalists sometimes recommend maca for thyroid problems, but you should consult your doctor before trying this herb – especially if your problem is hyperthyroidism as opposed to hypothyroidism – because it is usually recommended for the latter. Maca is not a well-studied herb, and most traditional medicinal use backs it as a libido booster and endurance enhancer, not as a thyroid treatment.
When you suffer hyperthyroidism, your thyroid gland is overactive and produces too much of the hormone thyroxine. This can alter your metabolism and lead to a rapid and irregular heartbeat, sudden weight loss, nervousness, irritability and sweating. Typical treatments for this condition include radioactive iodine and antithyroid medications that slow production of thyroid hormones or surgery to remove a portion of your thyroid gland. Hypothyroidism, on the other hand, is an underactive thyroid.
Theoretically you want to avoid maca if your thyroid is overactive because it may stimulate this gland. Maca is purported to boost an underactive thyroid, at least based on anectdotal evidence, according to "The Menopause Thyroid Solution," by Mary J. Shomon. Maca has a high iodine content, which is a major component of thyroid hormones. In theory, maca has hormone balancing properties and also helps boost your iodine levels, which in turn gives your thyroid a boost, according to "The Complete Herbal Guide," by Stacey Chillemi and Michael Chillemi. Iodine deficiency is not a common cause of underactive thyroid in the United States, however.
According to Memorial Sloan-Kettering Cancer Center, alkaloids in maca may affect your hypothalamic-pituitary axis, which directly affects your thyroid gland, though more research is needed to confirm this theory. While maca is reputed to balance hormones and enhance sexual performance, it does not appear to affect serum hormone levels of testosterone, estradiol, luteinizing hormone, prolactin or follicle stimulating hormone. Maca may act on the receptors for such hormones, however, because this herb appears to have estrogenic activity.
If you suffer an overactive thyroid, your best bet is to develop a treatment plan with your doctor. Taking maca is risky, because the toxic and therapeutic doses of maca remain unknown as of 2011.