Protective effect of citric acid on salivary gland function in patients with differentiated thyroid cancer after first ¹³¹I treatment

Objective: To investigate the effect of citric acid on the salivary gland function in the patients with differentiated thyroid cancer who received ¹³¹I treatment for the first time after operation, and to clarify the protective effect of citric acid on the salivary gland function in the patients with thyroid cancer who received ¹³¹I treatment. Methods: With the informed consent of the patients, 68 patients with thyroid papillary carcinoma who were going to receive ¹³¹I treatment were randomly selected and divided into control group and citric acid group (n = 34). There was no special preparation for the patients in control group, and the patients in citric acid group kept citric acid in the mouth for 1 min and spit it out every day (0.2 g/time) at 1 week before and 3 weeks after ¹³¹I treatment. The patients in two groups received ^99mTcO^4- salivary gland imaging twice within 24 h before ¹³¹I treatment and 3 months after ¹³¹I treatment. The uptake index in the fifteenth minute (15 min UI) and the secretion ratio (SR) were calculated and the salivary gland function was evaluated. Results: Compared with before ¹³¹I treatment, the 15 min UI of the right parotid gland and bilateral submandibular glands of the patients in control group after treatment had no significant differences (P > 0.05); the 15 min UI of left parotid gland after treatment was slightly decreased (P < 0.05); compared with before ¹³¹I treatment, the 15 min UI of the bilateral parotid glands and bilateral submandibular glands of the patients in citric acid group had no significant differences (P > 0.05). Compared with control group, the 15 min UI of bilateral parotid glands and bilateral submandibular glands of the patients in citric acid group before and after treatment had no significant differences (P > 0.05). Compared with before ¹³¹I treatment, the SR of bilateral parotid glands of the patients in control group after treatment were decreased (P < 0.05), and there were no differences in the SR of bilateral sub maxillary glands after treatment (P > 0.05). Compared with before ¹³¹I treatment, the SR of bilateral parotid glands and bilateral submandibular glands of the patients in citric group after treatment had no significant differences (P > 0.05). The SR of bilateral parotid glands of the patients in citric acid group after treatment were higher than those in control group (P < 0.05), but there were no significant differences in the SR of bilateral submandibular glands of the patients between two groups after treatment (P > 0.05). Conclusion: First ¹³¹I treatment may cause the damage of the secretion function of the salivary glands in the DTC patients after operation. Short-term administration of citric acid in the mouth can protect the salivary glands and alleviate the radioactive injury of the salivary glands. (authors)