Toxic Adenoma other imaging findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Overview
Radionuclide imaging and quantitative radioisotopic uptake studies are always required to establish the diagnosis of toxic adenoma or toxic nodular goiter. Radionuclide imaging can be performed with radioactive iodine-123 or with technetium-99m. In patients with hyperthyroidism caused by a toxic adenoma, there is a characteristic restriction of radionuclide uptake to the responsible hyperfunctioning nodule with suppression of radionuclide uptake in the remainder of the gland.
Other Imaging Findings
- Radionuclide imaging and quantitative radioisotopic uptake studies are always required to establish the diagnosis of toxic adenoma or toxic nodular goiter.[1]
- Radionuclide imaging can be performed with radioactive iodine-123 or with technetium-99m.[2][3]
- Radionuclide imaging performed with iodine-123 or technetium-99m, are trapped by the sodium-iodide symporter in functioning thyroid tissue, although only radioiodine is subsequently organified.
- In patients with hyperthyroidism caused by a toxic adenoma, there is a characteristic restriction of radionuclide uptake to the responsible hyperfunctioning nodule with suppression of radionuclide uptake in the remainder of the gland.
- In a patient with a low serum TSH concentration, not only does the scan appearance support the diagnosis of toxic adenoma, but in almost all cases it also excludes malignancy in the nodule.
- If some thyroid nodules are hypo functioning, it is necessary to rule out cancer by fine-needle aspiration cytology.
| Differential for thyrotoxicosis | Fractional Uptake
of Radioactive Iodine in 24 hrs (%) |
Radioactive iodine
Distrubution |
|---|---|---|
| Graves’ disease | 40-95 | Diffuse
(Homogeneous within thyroid) |
| Toxic adenoma | 20-60 | Restricted to autonomous regions in thyroid |
| Subacute thyroiditis | <2 | minimal uptake |
| Silent thyroiditis | <2 | minimal uptake |
| Iodine-induced thyrotoxicosis | <2 | minimal uptake |
| Factitious or | <2 | minimal uptake |
| Struma ovarii | <2 | Uptake in ovary |
| Follicular carcinoma | <2 | Uptake in cancer metastasis |
| Thyroid-stimulating hormone–induced thyrotoxicosis | 30-80 | Diffuse
(Homogeneous within thyroid) |
References
- ↑ Hurley PJ, Maisey MN, Natarajan TK, Wagner HN (1972). "A computerized system for rapid evaluation of thyroid function". J. Clin. Endocrinol. Metab. 34 (2): 354–60. doi:10.1210/jcem-34-2-354. PMID 4110446.
- ↑ Smith JR, Oates E (2004). "Radionuclide imaging of the thyroid gland: patterns, pearls, and pitfalls". Clin Nucl Med. 29 (3): 181–93. PMID 15162989.
- ↑ Bianco AC, Anderson G, Forrest D, Galton VA, Gereben B, Kim BW, Kopp PA, Liao XH, Obregon MJ, Peeters RP, Refetoff S, Sharlin DS, Simonides WS, Weiss RE, Williams GR (2014). "American Thyroid Association Guide to investigating thyroid hormone economy and action in rodent and cell models". Thyroid. 24 (1): 88–168. doi:10.1089/thy.2013.0109. PMC 3887458. PMID 24001133.