Thyroid Medicine & Herbs

There are numerous thyroid medications on the market, most of which in some way either suppress or, more likely, increase thyroid function. Another commonly prescribed class of thyroid medications is straight thyroid hormone supplements. Certain herbs that also act on the thyroid gland may interfere with the actions of many of these medications. People taking any sort of medication are advised to consult with their doctors before trying any herbal therapies, but people taking thyroid hormones or other thyroid medication should particularly avoid kelp, bugleweed, lemon balm and horseradish, along with the Ayurvedic herbs ashwagandha and guggul.

Kelp

Kelp is considered a helpful herb for the thyroid in that it is one of the rich dietary sources of iodine, an element instrumental in thyroid function. However, when combined with medication to boost thyroid activity, kelp could cause excessive thyroid hormone production, potentially turning a case of hypothyroidism into one of hyperthyroidism, and possibly taxing the thyroid gland, as well. Similar to kelp, and often mistaken for it, bladderwrack is also rich in iodine and also may exacerbate hyperthyroidism and interfere with hypothyroidism medications.

Bugleweed

Lycopus virginicus, commonly known as bugleweed, is a member of the mint family that inhibits certain antibodies associated with hyperthyroidism from binding to the thyroid gland. It is therefore most commonly used in herbal medicine to treat mild hyperthyroidism. In fact, according to Rudolf Fritz Weiss in "Herbal Medicine," it is considered safe for long-term use for this purpose. It contains lithospermic acid, among other organic acids, that cause a decrease in the levels of many hormones in the body, including thyroxine, a thyroid hormone, and thyroid stimulating hormones produced by the pituitary gland. As such, bugleweed could interfere with thyroid hormone supplementation or other medication to boost thyroid function and thyroid hormone production.

Lemon Balm

Another member of the mint family, Melissa officinalis, or lemon balm, contains rosmarinic acid, a substance known to bind to thyroid stimulating hormone, blocking its ability to stimulate thyroid function and therefore inhibiting thyroid activity. As such, lemon balm has been used to treat a type of hyperthyroidism called Graves disease. However, this same action may interfere with the actions of medication for hypothyroidism. Rosemary, or Rosmarinus officinalis, also contains rosmarinic acid, and is therefore similarly ill-advised for people on medication for hypothyroidism.

Horseradish

According to "Herbal Medicines: A Guide for Health-care Professionals," horseradish is not recommended for people with hypothyroidism, as it may further suppress the activity of the thyroid gland and interfere with the actions of prescription thyroid medication.

Ayurvedic Herbs

The root of the Withania somnifera plant is an adaptogen and tonic herb that was found in a 1999 study on mice to increase thyroxine activity and thyroid gland function. That same study also concluded that ashwagandha may change the effects that thyroid medications have on a person's body, including, possibly, the dosage needed to reap the anticipated benefits. Guggul, or Comniphora mukul, is a popular Ayurvedic herbal remedy for cholesterol. However, it has been found to raise levels of the thyroid hormone T3, or triiodothyronine.