The Role of Sodium Iodide Symporter in Autoimmune Thyroid Disease

Dr Philip Watson, The University of Sheffield

Final report

The aims of the project were:

1. To analyse the expression of the sodium iodide symporter (NIS) gene in human thyroid cells and other tissues.
2. To develop a novel assay for NIS autoantibodies using a recombinant cell line.
3. To use this new assay to study NIS autoantibodies in thyroid patients.
4. To study the possible relationship between NIS antibodies and other thyroid autoantibodies, and the possible correlation with the clinical status of patients.

The work has gone very well and we have successfully carried out a study of NIS gene expression, which was published this year (Ajjan et al 1998) The study showed the expression of the NIS gene in a range of tissues including stomach, salivary gland, mammary gland, and eye muscle.

We successfully expressed the human NIS gene and produced a novel bioassay for NIS autoantibodies. We were able to measure the level of NIS-modulated iodide uptake and study the effects of patient antibodies on this transport. Using the new assay we were able to assess the frequency of NIS-inhibitory antibodies in autoimmune thyroid disease patients. The results showed that approximately 27% of Graves' patients possess NIS autoantibodies that are capable of inhibiting iodide transport. This important study was recently published (Ajjan et al 1998). The work currently ongoing is to look at NIS antibodies in other thyroid patients and to attempt to isolate and study patient antibodies against this important antigen. These studies and the work described above have placed this group in the leading position in this area of research, and we are happy to acknowledge the support of the British Thyroid Foundation.