Immunohistochemical studies of Na⁺/I^- symporter in human thyroid tissues - A correlation with clinical thyroid scintigraphy

Background. Thyroid Na⁺/I^- symporter (NIS) is thought to play an important role in iodide uptake in thyrocytes. We hypothesize that there is correlation between the expression of NIS protein in the normal and diseased thyroid tissues and their clinical thyroid scintigraphy. Methods. Twenty-seven patients, aged from 21 to 81, were studied from the surgical department of a tertiary referral center. Ten patients were with papillary carcinoma, 5 with follicular carcinoma, 5 with follicular adenoma, 5 with nodular goiter and 2 with Graves' disease. All the carcinoma patients underwent total thyroidectomy while others had lobectomy or subtotal thyroidectomy. The thyroid tissue sections prepared for study were stained with polyclonal hNIS antibody (SS Chiang, Ohio). Results. Most of the nodular goiters were negatively stained except 2 samples that showed weak signal focally. All cases with follicular adenoma or follicular carcinoma were negative for NIS expression, while some with papillary carcinoma were stained positive at sporadic follicles with weak signal. The thyroid tissue of Graves' disease was stained positive for NIS expression. Conclusions. Thyroid tissues with hypofunctioning nodules displayed significantly reduced or undetectable level of NIS expression. It correlated well with pre-operative thyroid scans.