Radioiodine secretion in tears.
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.


CONCLUSIONS
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.
Department of Radiology, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
S M
SM
Bakheet
M M
MM
Hammami
A
A
Hemidan
J E
JE
Powe
F
F
Bajaafar
D000328:Adult; D002291:Carcinoma, Papillary / Q000628:therapy; D005137:Eye, Artificial; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007765:Lacrimal Apparatus / Q000528:radiation effects*; D008297:Male; D013666:Tears / Q000737:chemistry* / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000628:therapy; D013974:Thyroxine / Q000627:therapeutic use; D013997:Time Factors
D007457:Iodine Radioisotopes; D013974:Thyroxine