Biological characteristics of adenomatous nodules, adenomas, and hyperfunctioning nodules as defined by adenylate cyclase activity and TSH receptors

Epidermal growth factor receptors and adenylate cyclase activity in human thyroid tissues

Thyroid stimulating hormone (TSH) and epidermal growth factor (EGF) are growth factors for some thyroid cells in cultures. We have previously found more EGF receptors in neoplastic human thyroid tissues than in normal thyroid tissues. We have also found a higher TSH-stimulated adenylate cyclase (AC) activity in neoplastic human thyroid tissues than in normal thyroid tissues. To clarify the relationship between the effect of EGF and TSH on thyroid tissue, we measured the binding of EGF and TSH and the basal, TSH-stimulated and forskolin-stimulated adenylate cyclase activity in 49 normal, hyperplastic and neoplastic human thyroid tissues (5 normal, 2 Hashimoto thyroiditis, 5 Graves' disease, 14 multinodular goiters, 9 follicular adenomas, 5 follicular carcinomas, 8 papillary carcinomas, and 1 undifferentiated carcinoma). Specific binding of EGF and TSH were measured by radioreceptor assays using competitive inhibition of radio-labeled ligand by unlabeled ligand. Basal, maximally (300 mU/ml) TSH-stimulated, and maximally (100 mM) forskolin-stimulated adenylate cyclase activities were also measured in the same membrane particulate fractions from the thyroid tissues. We found: neoplastic thyroid tissues bind more labeled EGF than nonneoplastic thyroid tissues; follicular adenomas and carcinomas have higher EGF binding than other thyroid tissues; a weak but significant correlation between specific EGF binding and specific TSH binding, and between specific EGF binding and TSH-stimulated adenylate cyclase activity of the thyroid membrane preparations. These findings are consistent with the hypothesis that TSH stimulates an increase in thyroid EGF receptors by increasing intracellular cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of TSH receptors and microsomal antigen in different human thyroid tissue specimens

Affinity labelling with a 125I-labelled photoactive derivative of TSH (HSAB-TSH) was used to analyse TSH receptor size in the following specimens of human thyroid tissue: (1) cold nodules; (2) autonomous nodules; (3) papillary carcinoma; (4) medullary carcinoma; (5) metastasis of papillary carcinoma to lymph node; (6) anaplastic carcinoma, and (7) Graves' thyroid. In addition, a sample of histologically normal thyroid tissue surrounding specimens 1-4 was analysed in each case. Thyroid microsomes were also prepared from the tissue samples, solubilized using 1% deoxycholate and labelled with 125I. The preparations were immunoprecipitated using microsomal autoantibodies and protein A and analysed by SDS-PAGE and autoradiography. These studies indicated that no differences in the characteristics of the TSH receptor or of microsomal antigen were observed in the tissue samples 1-3 and 7. Neither protein was detected in tissue specimens 4-6.

Autoradiographical evidence for increased thyrotropin binding to autonomously functioning thyroid gland tissue

The aim of this study was to quantify thyrotropin (TSH) binding to individual cells from autonomously functioning thyroid gland tissue (AFTT) in comparison with the corresponding non-autonomous cells. Cryostatic tissue sections from ten thyroid glands with autonomously functioning adenomas were incubated in 125I-labeled TSH. TSH-binding density (TBD) was visualized by means of autoradiography and quantified by means of reflection photometry. Eight out of ten specimens showed a significant (p less than 0.001), up to tenfold increase in TBD of AFTT cells. All ten specimens had a significantly increased number of TSH molecules bound per thyrocyte in comparison both with the corresponding non-autonomous cells and also with tissues from non-functioning thyroid neoplasms (n = 6). The increased TBD of AFTT persisted after transplantation onto nude mice. The paranodular tissue from thyroid glands with scintigraphically compensated adenomas showed in four out of six cases an increased TBD when compared with normal thyroid tissue. It can be concluded that AFTT possesses distinct cytoplasm membrane characteristics as evinced by TSH binding analysis. Increased TSH binding should be considered as a possible cause of metabolic hyperactivity of AFTT cells. The concomitant existence of functional autonomy in the paranodular tissue might lead to a false supposition of a compensated autonomous adenoma as revealed by scintigraphical evidence.

Morphological demonstration and quantification of TSH binding sites in neoplastic and non-neoplastic thyroid tissues. An autoradiographic study using 125I-labelled thyrotropin

We have developed a morphological method to portray TSH binding sites in intact tissue specimens. Frozen sections were incubated with 125I-labelled TSH so as to localise binding sites by autoradiography. The proof of specificity was substantiated by: the competitive inhibition of 125I-TSH-labelling with cold TSH, the lack of binding in non-target tissues and a lack of binding in TSH target tissues after incubation with 125I-hCG or free 125I. In applying this method to a total of 22 surgical specimens of thyroid, striking differences came to light in respect of the degree to which 125I-TSH binding occurred in the various thyroid disorders. When compared with histologically normal tissue, labelling was generally decreased in toxic adenomas, non-functioning adenomas (cold nodules), and thyroids affected by Graves' disease, whereas non-toxic colloid goitre cases clearly exhibited denser binding. Medullary and anaplastic carcinomas exhibited no specific labelling whilst binding varied in the differentiated carcinomas between no effective binding or a level resembling that found in normal thyroid tissue.