Thyrotropin (TSH) stimulates cell growth and DNA synthesis in monolayer cultures of human thyrocytes independent of the adenylate-cyclase system.

Monolayer cultures of human thyrocytes from normal thyroids (n = 13), thyroid adenomas (n = 8), differentiated (n = 7), poorly and undifferentiated (n = 5) thyroid cancers as well as thyroid cancer metastases (n = 2) were established to assess the significance of TSH and cAMP on cell growth and DNA synthesis. Cell growth was stimulated by 0.1 IU bTSH/ml and inhibited by 1.0 IU bTSH/ml (P less than 0.01), while dibutyryl-cAMP (dbcAMP) failed to show any effect on cell growth at the concentrations (10-5; 10-3 mol/l), tested. Neither did the adenylate-cyclase inhibitor dideoxy-adenosine (ddA) (2 X 10-5 mol/l) stimulate thyrocyte growth. DNA synthesis, however, measured indirectly by [3H]thymidine incorporation, was stimulated not only by TSH 2-12-fold, but also by ddA 1.3-7-fold (P less than 0.01), and was not affected by dbcAMP. TSH had no effect on [3H]thymidine incorporation in fibroblasts and c-cells from c-cell carcinomas. The stimulatory effect of TSH on thyrocyte growth and DNA synthesis was unpredictable in thyrocytes from cancerous tissues (n = 14) with no obvious correlation to tumour differentiation or stage. Thus, we showed that TSH is a promotor for cell growth and DNA synthesis in monolayer cultures of human thyrocytes from normal and adenomatous human thyroid tissues with no obvious correlation to the AC system. This TSH effect is unpredictable, however, in thyrocytes from human thyroid cancer.