Thyrotoxic goitre. Goitre (swollen neck) seen on a woman patient suffering from an overactive thyroid gland. A goitre is caused by the enlargement of the thyroid gland and may vary in size from a small lump to an enormous swelling. Overactivity of the thyroid gland, also known as thyrotoxicosis, results in the overproduction of thyroid hormones in the body. This can result in symptoms ranging from weight loss and increased appetite to heart tremors and muscle wasting. Treatments include drugs to limit thyroid production or surgical removal of the thyroid.