In the first part of this study, we examined
TSH receptor (TSHR) and
thyroid hormone receptor (T3R beta) messenger
ribonucleic acid (
mRNA) levels in normal, hyperplastic, and neoplastic human thyroid tissue.
Tumor specimens from patients with different
thyroid carcinomas and
thyroid adenomas, and tissues from patients with
Graves' disease and from normal thyroid glands were analyzed by
solution hybridization and Northern blot using
complementary RNA probes. In the second part of the study,
mRNA analysis of T3R was extended to include the expression levels of each of the four T3R
isoforms alpha 1, alpha 2, beta 1, and beta 2. In neoplastic thyroid tissue such as papillary and follicular
carcinomas, the expression of both TSHR and T3R beta
mRNA per microgram total
RNA was significantly lower than that in normal thyroid tissue. The decrease in T3R beta
mRNA was shown to represent a specific and significant decrease in T3R beta 2
mRNA levels in particular, but also in the expression levels of T3R beta 1
mRNA. No differences were found in the expression levels of T3R alpha 1 or -alpha 2
mRNA. Furthermore, no differences in TSHR or T3R
mRNA levels were found in thyroid tissue from patients with
Graves' disease compared to normal thyroid tissue. It is concluded that the reduction of TSHR and T3R
mRNA in specific neoplastic thyroid tissues might be associated with the differentiation state of these
tumors and that the decrease in T3R
mRNA levels is due to a specific decrease in the expression levels of the T3R beta gene.