Bugleweed (Lycopus virginicus)


Hyperthyroidism and hyperthyroid-like symptoms including heart palpitations, tachycardia, chest tightness, tremor, and anxiety.

Mechanism of Action

Lycopus contains rosmarinic acid, a phenolic compound derived from caffeic acid and found in several other Lamiaceae plants, all indicated historically for the symptoms of hyperthyroidism. Rosmarinic acid, and the related lithospermic and chlorogenic acids, may exert an antithyroid effect in cases of hyperthyroidism.

When thyroid-stimulating hormone (TSH) binds to the outer membrane of thyroid cells, it triggers a cAMP response on the inside of the cell via adenylate cyclase enzyme activation. Rosmarinic acid seems to slow TSH-driven stimulation of thyroid cells, via adenylate cyclase inhibition,1 and whole Lycopus extract may calm excessive thyroid stimulation, as with Grave’s disease and autoimmune thyroiditis, via adenylate cyclase blockade.2 Rosmarinic acid also forms “adducts” with TSH, meaning that owing to particular electromagnetic affinities, rosmarinic acid forms lose bonds with endogenous TSH, thereby reducing its ability to bind and agonize TSH receptors.3 This may reduce thyroxine output in cases of hyperthyroidism.

Lycopus also inhibits the ability of Grave’s autoantibodies to bind to TSH receptors and promote intracellular cAMP responses, thereby reducing adenylate cyclase–driven signal transduction and the resulting increase in thyroid hormone output.4,5

Evidence-Based Research

Scientific studies on Lycopus are extremely limited, but one animal study reported Lycopus europaeus to reduce elevated heart rate, blood pressure, and hyperthermia in a model of hyperthyroidism.6

Aqueous extracts from Lycopus have been shown to have antihormonal components that inhibit the enzymatic deiodination processing of thyroxine outside of the thyroid gland, suggesting therapeutic value in the treatment of hyperthyroidism.7

One human clinical study investigated the effects of L. europaeus on tri-iodothyronine (T3) and thyroxine (T4) urinary excretion, serum hormone levels, and general subjective and objective symptoms in hyperthyroid subjects. Patients treated with Lycopus for 3 months displayed significantly increased urinary excretion of T4 compared with controls, the proposed mechanism being either glomerular effects or interference with renal resorption of T4. Elevated heart rate was reportedly reduced in the hyperthyroid patients experiencing this symptom.8

Another clinical cohort study evaluated clinical outcomes in groups of hyperthyroid patients using Lycopus extracts in various time frames, compared with a cohort of hyperthyroid patients receiving no treatment. The groups receiving the L. europaeus were associated with a statistically significant and clinically relevant improvement of the symptoms in mild hyperthyroidism.9

Safety in Pregnancy and Breastfeeding

No published studies have been identified that test the safety of Lycopus in either pregnancy or breastfeeding.

General Safety

The few clinical studies that have been done report Lycopus to be well tolerated and without significant side effects.


Lycopus is generally considered safe and can be taken at doses ranging from 100 to 400 mg at a time for two to three times each day. Higher doses of 2 g or more a day have been well tolerated.

Traditional Uses

Lycopus virginicus is used in the folk medicine of old Europe and by early American herbalists as a sedative and cough remedy and for tumultuous heart action. Other species of Lycopus also go by the common name bugleweed including L. americanus, L. europaeus, and L. lucidus. They are all used medicinally in similar ways for hyperthyroid-like symptoms including heart palpitations and tachycardia, chest tightness, tremor, anxiety, and insomnia.



Endocrinology. 1984;115(2):527–34. Inhibition by certain plant extracts of the binding and adenylate cyclase stimulatory effect of bovine thyrotropin in human thyroid membranes. Auf’mkolk M, Ingbar JC, Amir SM, Winterhoff H, Sourgens H, Hesch RD, Ingbar SH.

2 Plant-Med. 1990;56(6):683. Rosmarinic acid and freeze-dried extract (FDE) of Lycopus virginicus are able to inhibit forskolin-induced activation of adenylate cyclase in cultured rat thyroid cells. Kleemann S, Winterhoff H. Stuttgart, W. Ger.: Georg Thieme Verlag.

3 Endocrinology. 1985;116(5):1677–86. The active principles of plant extracts with antithyrotropic activity: Oxidation products of derivatives of 3,4-dihydroxycinnamic acid. Auf’mkolk M, Amir S, Kubota K, Ingbar S.

4 J Endocrinol Invest. 2003;26(10):950–5. In vitro assay of thyroid disruptors affecting TSH-stimulated adenylate cyclase activity. Santini F, Vitti P, Ceccarini G.

5 Endocrinology. 1985;116(5):1687–93. Extracts and auto-oxidized constituents of certain plants inhibit the receptor-binding and the biological activity of Graves’ immunoglobulins. Auf’mkolk M, Ingbar JC, Kubota K, Amir SM, Ingbar SH.

6 Life Sci. 2006;78(10):1063–70. Extract of Lycopus europaeus L. reduces cardiac signs of hyperthyroidism in rats. Vonhoff C, Baumgartner A, Hegger M, et al.

7 Horm Metab Res. 1984;16(4):188–92. Antihormonal effects of plant extracts: iodothyronine deiodinase of rat liver is inhibited by extracts and secondary metabolites of plants. Auf’mkolk M, Köhrle J, Gumbinger H, et al.

8 Phytomedicine. 2008;15(1):16–22. Lycopus europaeus (Gypsywort): Effects on the thyroidal parameters and symptoms associated with thyroid function. Beer AM, Wiebelitz KR, Schmidt-Gayk H.

9 Wien Med Wochenschr. 2013;163(3–4):95–101. Improvement of symptoms in mild hyperthyroidism with an extract of Lycopus europaeus (Thyreogutt® mono). Eiling R, Wieland V, Niestroj M.