Causes of hyperthyroidism

The causes of hyperthyroidism are: 

• Graves-Basedow disease (GBD) is the most common cause of hyperthyroidism (60-70%). This is an autoimmune disease in which antibodies are synthesised that stimulate the thyroid gland to grow and overproduce thyroid hormones.  
• Multinodular or nodular goitre. The thyroid has several nodules that can slowly grow and begin to over-synthesise thyroid hormones, eventually causing hyperthyroidism. A toxic (overactive) adenoma is a thyroid nodule that secretes too much thyroid hormone. This inhibits the production of thyroid hormone by the rest of the gland. This nodule may occur within a thyroid or within a multinodular (multi-nodular) goitre. These are more common with age and iodine deficiency.  
• Pituitary Gland Tumours. This is a rare cause that occurs when a pituitary tumour produces an excess of thyrotropin (TSH), a hormone that stimulates the thyroid gland to produce thyroid hormones in an unregulated manner. As it synthesises so many hormones, the thyroid gland becomes less sensitive to them and develops resistance.  
• Thyrotoxicosis. This is a set of symptoms caused by high concentrations of circulating thyroid hormones. It may be caused by taking too much thyroxine in pill form; through inflammation and destruction of the thyroid involving the transient release of hormones into the bloodstream, as in thyroiditis; or by having an overactive thyroid (hyperthyroidism).