Radioiodine secretion in tears.

Unlabelled: Lacrimal secretion of radioiodine has been suspected from previous scintigraphic observations. We semiquantitated radioiodine secretion in the tears of a thyroid-ablated patient with an artificial eye while the patient was on thyroxine treatment.
Methods: After an oral dose of 555 MBq (15 mCi) 123I, 12 tear samples were collected over 24 hr by using Schirmer papers. Radioactivity in each sample was determined in a well counter 27 hr after radioiodine ingestion and was corrected for decay and counting efficiency.
Results: Radioactivity was detectable at 15 min and at up to 24 hr after radioiodine ingestion and peaked at around 60 min (215 Bq/microl or 39 x 10(6)% of the administered dose/microl. Considering a tear-flow rate of 1 microl/min, the total radioactivity secreted in the first 4 hr was estimated to be 56 kBq, representing about 0.01% of the administered dose.
Conclusion: An appreciable amount of ingested radioiodine could be secreted in tears. The potential damage of the lacrimal gland after high doses of 131I treatment deserves further study.