Quantitative measurements of the thyroid can be performed to calculate the iodine uptake (absorption) for the diagnosis of hyperthyroidism and hypothyroidism.
Radioactive iodine, as developed in 1911, survives today primarily in the treatment of thyrotoxicosis (hyperthyroidism) and some types of thyroid cancer that absorb iodine.
The same three treatments used with humans are also options in treating feline hyperthyroidism (surgery, radioiodine treatment, and anti-thyroid drugs).