RADIOIODINE SECRETION IN TEARS

Lacrimal secretion of radioiodine has been suspected from previous sci ntigraphic observations. We semiquantitated radioiodine secretion in t he tears of a thyroid-ablated patient with an artificial eye while the patient was on thyroxine treatment. Methods: After an oral dose of 55 5 MBq (15 mCi) I-123, 12 tear samples were collected over 24 hr by usi ng Schirmer papers. Radioactivity in each sample was determined in a w ell counter 27 hr after radioiodine ingestion and was corrected for de cay and counting efficiency. Results: Radioactivity was detectable at 15 min and at up to 24 hr after radioiodine ingestion and peaked at ar ound 60 min (215 Bq/mu l or 39 x 10(-6)%) of the administered dose/mu l. Considering a tear-flow rate of 1 mu l/min, the total radioactivity secreted in the first 4 hr was estimated to be 56 kBq, representing a bout 0.01% of the administered dose. Conclusion: An appreciable amount of ingested radioiodine could be secreted in tears. The potential dam age of the lacrimal gland after high doses oi I-131 treatment deserves further study.