Profile photograph of the face of a man suffering from thyrotoxicosis, showing his abnormally- bulging eyes (exophthalmos). Protrusion of the eyes (exophthalmos) is one symptom of a form of thyrotoxicosis known as Graves's disease. Thyrotoxicosis describes an excess of thyroid hormones in the blood, which causes a rapid heart beat, sweating, tremor, anxiety, increased appetite, weight loss and intolerance of heat. Causes include simple overactivity, benign or cancerous tumours of the thyroid gland, and Graves's disease, where there are additional symtoms of swelling of the neck (goitre) and protrusion of the eyes.