Presentation
Episodic palpitations, diaphoresis, and weight loss.
Patient Data
Anterior distant image obtained with Tc-99m-pertechtenate shows that the gland is enlarged. Activity throughout gland is increased relative to the background due to hyperfunctionality of the gland.
The pyramidal lobe (remnant of the thyroglossal duct) is visualized projecting cephalad from isthmus (red arrow). The pyramidal lobe is usually not seen (because it is small) unless the gland is overly stimulated.
Case Discussion
When interpreting scintigraphic images it is important to have the information about the patient's history and physical, especially assessment of the thyroid gland, where the majority of evaluations take place. Uniformity and intensity of the image of the organ in evaluation and background should be observed. Variations in function of focal areas should also be noted, making specific comparisons between foci of increased or decreased function relative to the background activity in the remaining of the extrafocal tissue.
Potential sources of error include local contamination (e.g. clothing, skin, hair, collimator, crystal), esophageal activity (e.g. hiatal hernia), suppression of iodine uptake by interfering substances. Asking the patient to rinse their mouth with water and then swallowing is sometimes useful to eliminate activity by the mouth or the esophagus.
Anticipated results: RAIU in the evaluation of thyrotoxicosis, namely Graves disease, is commonly elevated at 24 hours. In patients with substantially increased thyroid hormone synthesis and turnover, 4-hour and 6-hour RAIU may be elevated while 24-hour uptake is within normal limits. This patient demonstrated increased RAIU at both 4 and 6 hours.
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