**8. Adverse effects**

Some patients, especially those who have large thyroid mass, may notice a transient swelling of goiter for approximately one week after therapy, salivary gland discomfort, or dyspnoea. Nausea that could develop into vomiting depends on the amount of administered activity for RAI. Antiemetic treatment can reduce the symptom. The effects are infrequent when the patients received <1.1 103 MBq (<30 mCi). Those effects are usually observed on a high dose >3.7 103 MBq (> 100 mCi) of RAI [29].

RAI treatment can cause a transient exacerbation of hyperthyroidism. The β- adrenergic blocker should be considered in symptomatic and asymptomatic patients who have hyperthyroidism risk (i.e., elderly patients and patients with comorbidities) [6]. Even though it is rare, the radiation can induce thyroiditis and thyroid hormone release into the circulation leading to thyroid storm precipitation [4, 6, 12]. The condition is more likely occurring in patients with a large thyroid mass and who received higher RAI activities. Elderly patients and patients with significant pre-existing heart disease, severe systemic illness, or debility may benefit from pre-treatment with ATDs. However, ATDs should be withdrawn for one week before RAI therapy and resumed a week afterward [4, 6, 23, 25].

The aim of RAI therapy in GD is to control hyperthyroidism and render hypothyroidism. It is easier to manage hypothyroidism with levothyroxine and fewer complications compared to treat hyperthyroidism with ATDs in the long term, leading to undesirable therapy effects [30]. The number of mortality reduced in hyperthyroid patients who become hypothyroidism after RAI therapy. The condition is implying the survival advantages of hyperthyroidism control. The risk of mortality of patients with hyperthyroidism, whether caused by cardiovascular or cancer, appears to be driven by thyroid hormone excess [4, 31].
