Hyperthyroidism is a medical condition where the thyroid gland produces too much thyroid hormone. This can make a person's metabolism work too fast, leading to symptoms like weight loss, fatigue, and increased heart rate. Full definition
Many veterinary endocrinologists also believe that blocking the excessive T4 production of hyperthyroidism with diets such as y / d does not deal with the cat's underlying problem - abnormal overactive hormone - producing cells in its thyroid gland. (2ndchance.info)
This isn't often the case with hyperthyroidism in cats after TWO years without treatment. (askthecatdoctor.com)
I - 131 (radioactive iodine) suite for treatment of hyperthyroidism in cats complete with observation cameras. (vscot.com)