Noun | 1. | ![]() hyperthyroidism, thyrotoxicosis - an overactive thyroid gland; pathologically excessive production of thyroid hormones or the condition resulting from excessive production of thyroid hormones autoimmune disease, autoimmune disorder - any of a large group of diseases characterized by abnormal functioning of the immune system that causes your immune system to produce antibodies against your own tissues exophthalmos - protrusion of the eyeball from the socket |