Final answer:
The MC lab test to check for thyroid function typically involves blood tests for thyroid hormone levels, particularly thyroxine. Advanced diagnostics may use radioisotope scanning with radioactive iodine to assess the gland's activity, which can indicate hypothyroidism if iodine uptake is low.
Step-by-step explanation:
The MC lab test to check for thyroid function commonly includes measuring the levels of thyroid hormones in the blood. The test may specifically measure levels of thyroxine (T4), a hormone produced by the thyroid gland that regulates energy usage in the body. In cases of hypothyroidism, where the thyroid produces less T4, patients may experience fatigue and weight gain. This condition is treated with thyroid hormone supplements.
Advanced diagnosis may involve the administration of radioactive iodine isotopes, such as Na¹³¹I or Na¹²¹I. These isotopes accumulate in the thyroid and allow for the assessment of gland function through radioisotope scanning. A scintillation counter can measure iodine ¹³¹ uptake to evaluate thyroid activity. A normal functioning thyroid gland will absorb more iodine, resulting in less being excreted in the urine—a determinant in assessing gland health.