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Indian J Nucl Med. 2020 Jan-Mar;35(1):17-20. doi: 10.4103/ijnm.IJNM_158_19. Epub 2019 Dec 31.

Radioiodine Therapy of Graves' Disease and the Uptake Paradox.

Author information

Department of Radiotherapy, Nuclear Medicine Division, Kasturba Medical College, Manipal, Karnataka, India.
Department of Nuclear Medicine, AMRI Hospital, Kolkata, West Bengal, India.
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.


Purpose of the Study:

Radioiodine (131I) therapy is approved and well-accepted modality for the treatment of hyperthyroidism. The dosage of 131I for successful treatment is based on many factors; however, an objective tool to determine the dose was missing. In a retrospective study, we found that high 131I uptake values required more dose to achieve desirable results contrary to the belief.

Materials and Methods:

Clinically and scintigraphically proven Graves' disease patients with high 131I uptake (>50%) were accrued for this study and block randomized into low-dose (Group I) and high-dose (Group II) groups. Low activity (5 mCi) was administered in Group I and higher activity (10 mCi) in Group II. The patients were followed up after 3 months with thyroid function tests to determine the outcome.


A total of 344 patients were analyzed at the end of 3 months, with 174 in low-dose group and 170 in high-dose group. Euthyroidism/hypothyroidism was achieved in significantly higher number of patients as compared to the low-dose group.


The higher dose of 131I is required to achieve euthyroidism/hypothyroidism in patients with high 131I uptake.


Hyperthyroidism; radioiodine therapy; radioiodine uptake

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