Lithospermic acid and other organic acids are believed to be responsible for bugleweed’s activity. These acids decrease levels of several hormones in the body, particularly thyroid-stimulating hormones¹ and the thyroid hormone thyroxine (T4).² Bugleweed inhibits the binding of antibodies to the thyroid gland.³ These antibodies can cause the most common form of hyperthyroidism, Graves’ disease. All these actions may help explain bugleweed’s benefit in people with mildly overactive thyroids.