EFFECT OF TESTOSTERONE ON TSH AND THE DEVELOPMENT OF THYROID TUMORS IN RATS INDUCED BY N-BIS(2-HYDROXYPROPYL)-NITROSAMINE

抄録

Effects of testosterone(17α-methyl testosterone) on the serum concentration of TSH(thyroid stimulating hormone) and on the development of thyroid tumors were studied in castrated rats pretreated with N-bis(2-hydroxypropyl) nitrosamine(DHPN). In addition, the dose dependency of testosterone on serum TSH concentration was assessed in castrated animals. The incidences of thyroid tumors induced by DHPN were 69% in non-castrated rats, 40% in castrated rats, 85% in castrated rats treated with 300 ppm testosterone diet, 21% in castrated rats treated with 1500 ppm testosterone diet, 20% and 6% in non-castrated rats treated with 300 ppm or 1500 ppm testosterone diet, respectively. The mean serum TSH concentration in castrated rats treated with DHPN and 1500 ppm testosterone diet showed a tendency of higher than the other group values, but not significantly, and the incidences of thyroid tumors did not demonstrate any clear relation to serum TSH concentration values. The serum TSH concentrations were 2.86±1.86 ng/ml in non-castrated rats and 2.80±0.16, 2.57±0.21, 2.43±0.92, 2.10±0.59, 3.09±1.03, 2.73±0.80 and 3.58±0.16 ng/ml in castrated rats fed on diets containing 0, 100, 300, 600, 900, 1200 and 1500 ppm testosterone, respectively. A dose dependent influence of testosterone on mean seminal vesicle and prostate weights but not on serum TSH concentration as well as thyroid weights was observed. The results, thus, suggest that higher concentration of testosterone without higher concentration of TSH inhibits the development of thyroid tumors in rats treated with DHPN.