title: Age and sex difference in serum and pituitary thyrotropin concentrations in the rat: influence by pituitary adenoma.
abstract: Effects of age and sex difference on serum and pituitary thyrotropin (TSH) concentrations were investigated in young (4 to 6 months) and old (28 to 36 months) Long-Evans rats with or without pituitary tumor. Basal and TRH-induced serum TSH concentrations in young males are significantly (P less than .05) higher than in old males, while there is no significant difference in basal TSH between young and old female rats, but young females had greater TSH response to TRH than the old females. Orchidectomy significantly reduced plasma TSH in the young but not in the old male rats. Administration of testosterone propionate reversed the castration effects on TSH in the young male rat. Ovariectomy significantly reduced plasma TSH in the old but not in the young female rats. Estrogen treatment slightly increased basal TSH concentrations in both the young and old rats.
mesh_terms: D000236:Adenoma / Q000503:physiopathology*; D000367:Age Factors; D000375:Aging; D000818:Animals; D002369:Castration; D004958:Estradiol / Q000502:physiology; D005260:Female; D008297:Male; D010903:Pituitary Gland, Anterior / Q000032:analysis*; D010911:Pituitary Neoplasms / Q000503:physiopathology*; D011863:Radioimmunoassay; D051381:Rats; D012737:Sex Factors; D013739:Testosterone / Q000502:physiology; D013972:Thyrotropin / Q000032:analysis* / Q000097:blood; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000502:physiology
chemical_list: D013739:Testosterone; D004958:Estradiol; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin