EFFECTS OF HYPERTHYROIDISM AND RADIOACTIVE IODINE GIVEN TO ABLATE THETHYROID ON THE COMPOSITION OF WHOLE STIMULATED SALIVA

OBJECTIVE For many years there has been speculation about possible dam age to the salivary glands following administration of ablative doses of radioactive iodine for treatment of hyperthyroidism. We have invest igated the changes that occur in the composition of saliva in hyperthy roidism and after the administration of an ablative dose of radioactiv e iodine to hyperthyroid subjects. DESIGN The study consisted of two p arts: first, a comparison of a group of hyperthyroid patients with a g roup of normal subjects with regard to the concentration or activity o f 10 constituents of saliva; second, measurement of those constituents 3-42 weeks after administration of 370 MBq of radioactive iodine to a group of hyperthyroid subjects. PATIENTS Saliva specimens from 38 unt reated outpatients with hyperthyroidism due to Graves' disease or toxi c nodular goitre were studied to evaluate the effects of hyperthyroidi sm and the results were compared with a group of 93 normal subjects. S eventy-one samples of saliva from 26 patients with persistent hyperthy roidism were collected and analysed 3-42 weeks after radioactive iodin e administration. MEASUREMENTS The flow rate; the concentrations of to tal protein, iodine, calcium, urate, phosphate, potassium and immunogl obulin A; and the activities of N-acetylglucosaminidase, lysozyme and lactate dehydrogenase were measured. RESULTS In hyperthyroidism the sa livary flow rate and the concentrations of urate and potassium were si gnificantly (P < 0.05) increased and the concentrations of total prote in, calcium and lactate dehydrogenase activity significantly decreased compared to the control group. After radioactive iodine was administe red, significant positive trends were observed in the concentrations o f total protein, N-acetylglucosaminidase and immunoglobulin A. These t rends were independent of the free T3 levels obtained from the same sp ecimens. CONCLUSIONS Hyperthyroidism leads to a number of changes in s alivary composition. For most of the salivary components measured no s ignificant changes were observed 3-42 weeks after administration of 37 0 MBq of radioactive iodine to patients with persistent hyperthyroidis m. The relatively small positive trends in the concentrations of total protein, N-acetylglucosamidase activity and immunoglobulin A may have been due either to changes in thyroid status or to the effects of rad iation on the salivary glands, or both.