Endocrine Abstracts

JOINT876

Objective: This study aimed to evaluate the effectiveness and thyroid status outcomes following the introduction of a fixed radioactive iodine (RAI) dose of 600 Mbq in patients diagnosed with hyperthyroidism.

Methods: A retrospective review was conducted involving 92 patients treated for hyperthyroidism after the implementation of the fixed 600 Mbq RAI dose. The analysis focused on primary diagnoses, biochemical outcomes, and the duration of hypothyroidism development in patients post-RAI, as well as the initiation of levothyroxine therapy.

Results: Among the 92 patients studied, 67 were diagnosed with Graves’ disease and 25 with multinodular goitre (MNG). The cohort comprised 72% females and 26% males, with an average age of 54.8 years. The overall cure rate was 89%, surpassing the 83.5% cure rate reported in previous studies involving variable doses of RAI. Antithyroid medication (ATD) was discontinued in 91% of Graves’ patients on average 11.3 weeks after RAI, compared to 84% of MNG patients who ceased ATD therapy an average of 11.7 weeks post-RAI. The average time to hypothyroidism development was 13.38 weeks for Graves’ patients and 22.1 weeks for those with MNG. In patients with Graves’ disease, 84% initiated levothyroxine therapy, while only 40% of MNG patients required thyroxine supplementation post-RAI.

Conclusion: The overall cure rate was 89%, indicating a significant improvement over variable dose RAI outcomes documented in other studies, with 91% of Graves’ patients and 84% of MNG patients discontinuing ATD therapy on average 11.3 and 11.7 weeks post-RAI, respectively. The administration of 600 Mbq RAI is associated with a lower incidence of hypothyroidism requiring thyroxine supplementation in patients with MNG, and hypothyroidism develops later compared to those with Graves’ disease. As previously known, RAI for toxic MNG is an effective treatment that can result in euthyroidism, with fewer patients requiring levothyroxine replacement. We intend to use the results to implement a streamlined outpatient follow-up approach, where thyroid function tests can be organized at 6 weeks via a virtual clinic, with the first face-to-face appointment scheduled between 11 to 12 weeks, thus reducing the need for earlier and more frequent appointments. This approach may potentially enhance patient care by improving access, increasing time efficiency, enabling early detection of complications, and boosting patient satisfaction.

Reference: Fixed 600mbq radioiodine activity is more effective than variable dose in treatment of benign thyroid disease) [(Mohamed et al., 2019)]