If the patient is not breastfeeding, thyroid scan and RAIU test can safely be performed to help elucidate the diagnosis. RAIU is elevated with hyperthyroidism due to Graves disease, solitary autonomous nodule, or TMG. RAIU is low with hyperthyroidism due to thyroiditis.1 If the patient has been exposed to exogenous iodine (eg, radiocontrast dye injection), RAIU will also be low, even if the patient has Graves disease; it can take up to 3 months to obtain an accurate RAIU result in such cases. Although a thyroid ultrasound would identify possible gland enlargement and/or thyroid nodules, it would not provide information about glandular activity/function. In addition, the presence of TSH receptor antibodies may suggest Graves disease; however, this provides no information about glandular activity/function. Retesting of TSH and FT4 levels would confirm abnormal results but would not provide information regarding the etiology of thyrotoxicosis in this patient.
- Thyroid scan and RAIU.
1. Abalovich M, Amino N, Barbour LA, et al. Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2007;92(8 Suppl):S1–47.
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