THYROID-UPTAKE SCAN
SUMMARY
Thyroid uptake scan: radioactive iodine uptake (RAIU) & scintigraphy scan. Carried out if hyperthyroidism is detected.
INCREASED RAIU (increased iodine uptake)
1. Primary hyperthyroidism: Grave's disease, toxic or active thyroid nodules (solitary or toxic MNG)
2. Secondary hyperthyroidism: TSH secreting pituitary tumor, hCG secreting tumor
3. Decreased iodine availability (hence increased uptake): iodine deficiency
DECREASED RAIU (decreased iodine uptake)
1. Hypothyroidism: thyroiditis (RAIU differentiates Graves from thyroiditis; in Graves the gland is producing more, in thyroiditis the gland is just inflammed).
2. TSH suppression: exogenous T3 or T4, factitious hyperthyroidism
3. Increased iodine availability: iodine excess
SCINTIGRAPHY SCAN (pattern of uptake)
1. Hot nodule: hyperfunctioning gland
2. Cold nodule: hypofunctioning gland, likely malignancy
Reference(s)
Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].
