EFFECT OF TSH ON cAMP AND cGMP LEVELS IN THYROID CANCERS, ADENOMAS AND NORMAL HUMAN THYROID TISSUE

ABSTRACT The effect of TSH (50 mU/ml) alone or in combination with theophylline (10 mm) on the cAMP level in human thyroid tissue after a 10 min incubation has been studied in 8 normal tissues, 7 adenomas and 10 thyroid cancers (8 differentiated and 1 anaplastic). Our results have shown the lack of responsiveness to TSH in the 2 anaplastic carcinomas studied, as well as in 4 cases among the 8 differentiated cancers studied. In thyroid adenomas, on the contrary, the cAMP increase in response to TSH was close to that observed in normal tissues. In these adenomas, the mean basal cAMP level (0.43 ± 0.07 pmol/mg tissue) was not statistically different from that in normal tissues (0.36 ± 0.06), while in thyroid cancers the mean basal cAMP level (0.93 ± 0.26) was significantly greater than that in normal tissues (P < 0.05). The cGMP level was measured in the same conditions in 7 normal thyroid tissues and 8 thyroid cancers (7 differentiated and 1 anaplastic). The mean basal cGMP level in these cancers (9 ± 1 fmol/mg tissue) was not statistically different from that in normal tissues (12 ± 2). In response to TSH, no increase of cGMP level was observed in cancers, or in the normal tissues. The disorders of hormone synthesis previously seen in human thyroid cancers did not appear related to a decreased cAMP content, but might be due to a lack of responsiveness to TSH in undifferentiated cancers and in some cases of differentiated carcinomas.