Your thyroid, which is a gland located in the lower part of your neck, produces certain hormones. This production is stimulated by the pituitary gland in the brain, which regulates hormone production in the body. In the case of hyperfunctioning thyroid nodules, non-cancerous nodules start growing in the thyroid, causing it to produce too many hormones. This results in too much thyroxine (a hormone produced by the thyroid) and too little TSH (a hormone produced by the brain). The condition is also known as toxic thyroid adenoma and contributes to hyperthyroidism.