U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska


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Date of this Version



Published in J. Reprod. Fert. (1982) 64, 449-455


The effects of s.c. administration of oil, testosterone, 5α-dihydrotestosterone, 5α-androstane-3α,17β-dioland oestradiol-17β on plasma concentrations of LH and FSH were determined in 5 orchidectomized dogs. The dosages for the androgens and oestradiol-17β were 500 and 50 μg/kg body weight, respectively. Testosterone and oestradiol-17β significantly reduced plasma gonadotrophin concentrations, although the onset and duration of their suppressive effects differed. Dihydrotestosterone and oil had no effect on either gonadotrophin. Administration of androstanediol had no effect on plasma concentrations of LH but did cause a temporary and significant reduction in FSH. It is concluded that testosterone and oestradiol-17β are major regulators of gonadotrophin secretion in the male dog, but the 5α-reductionof testosterone seems to play only a minor role in this control.