From the Research
An elevated T3 uptake test indicates decreased binding protein capacity in the blood, which typically suggests hyperthyroidism. This test measures the availability of binding sites on thyroid-binding proteins, particularly thyroxine-binding globulin (TBG) 1. When T3 uptake is high, it means there are fewer available binding sites because they're already occupied by thyroid hormones, or there's a decreased amount of binding proteins. Common causes include hyperthyroidism (where excess thyroid hormone production saturates binding proteins), decreased TBG levels (seen in liver disease, protein-losing conditions, or with medications like androgens and glucocorticoids), or familial dysalbuminemic hyperthyroxinemia.
Some key points to consider:
- Hyperthyroidism is an excess in thyroid hormone production caused by such conditions as Graves disease, toxic multinodular goiter, and toxic adenoma 1.
- The long-term consequences of unmanaged or poorly managed hyperthyroidism include increased risk of all-cause mortality, cardiovascular events, atrial fibrillation, sexual dysfunction, and osteoporosis 1.
- It's essential to interpret T3 uptake in conjunction with other thyroid tests like TSH, free T4, and free T3 for accurate diagnosis.
- The test is now less commonly used, as direct measurement of free thyroid hormones provides more reliable information about thyroid function 2.
- If you have an elevated T3 uptake, your healthcare provider will likely order additional tests to determine the specific cause and appropriate treatment.
In terms of management, overt and subclinical hyperthyroidism can be managed effectively with antithyroid drugs (eg, propylthiouracil, methimazole) or with definitive therapies (eg, radioactive iodine ablation, thyroidectomy) 1. Treatment for subclinical hyperthyroidism is recommended for patients 65 years or older with TSH levels lower than 0.10 mIU/L, symptomatic patients, or those with cardiac or osteoporotic risk factors 1.