In layman terms, the above paragraph simply means the thyroid gland controls the cat's metabolism. The thyroid gland produces the thyroid hormones that are critical to maintaining the cat s normal metabolic rate. This is the speed at which the body converts nutrient energy into energy fueling the body. If the thyroid gland degenerates or becomes inflamed, it can no longer produce sufficient quantities of hormones. As a result, cells don t convert the nutritional energy it needs into biologically usable fuel as fast as usual.
Feline hypothyroidism is rare in cats, though hyper thyroidism is much more common.
Hypothyroidism occurs when there is too little thyroid hormone in the cat's blood - an under active thyroid gland. If thyroid hormones are given to test whether it is the problem, the cat may show hair growth even though hypothyroidism may not be the problem. This is because the hormones generally stimulates the body. If it is overactive, the metabolism speeds up and is called hyper thyroidism . Unexplained weight gain can be a sign of a medical problem such as hypothyroidism.