Final answer:
Radioactive isotopes such as iodine-131 are used to diagnose thyroid problems by measuring the uptake of radioactive iodine by the thyroid gland, allowing for the detection of overactive or underactive thyroid conditions.
Step-by-step explanation:
Radioactive isotopes, particularly iodine-131, are used in the medical diagnosis and treatment of thyroid problems. These isotopes are helpful because the thyroid gland naturally concentrates iodine from the bloodstream to synthesize crucial hormones. For diagnostic purposes, a measured dose of iodine-131 is introduced into the patient's body, and then the amount of radioactivity in the thyroid gland is scanned on the following day using special equipment. The uptake of radioactive iodine by the thyroid gland is the key measurement, as it is directly related to the gland's activity, allowing for the diagnosis of conditions like hyperthyroidism and hypothyroidism. Technetium-99 can also be used to test thyroid function. Therefore, the correct answer is Option 2: Uptake of radioactive iodine by the thyroid gland is measured.