358 i{. .1. Goss 



observations of Wislocki et al. ( 1947 ) and Waldo and W'islocki 

 (1951), who showed that testosterone administered to normal Vir- 

 ginia deer in winter and spring delayed the normal shedding of 

 antlers for several months. They show further that estrogen exerts 

 effects very similar to those of testosterone on the antlers of adult 

 deer, and corroborate the earlier observations of Blauel (1935) that 

 the antlers of castrated roe bucks are not shed until almost 2 months 

 after injections of estrogen (Progvnon) cease. 



Castration-induced shedding mav be simplv a withdrawal s\ mp- 

 tom based upon testosterone depletion. Alternatively, the drop in 

 testosterone levels may be attended by a rise in the amounts of other 

 hormones secreted, one of which might directlv stimulate osteoclastic 

 activity at the pedicle-antler junction. Since it is well known that 

 the secretion of gonadotropins from the pituitary increases when the 

 target organs are removed, an experimental attempt to inhibit the 

 secretion of these hormones was undertaken bv administering the 

 contraceptive Enovid * to 4 castrated bucks. Injection schedules 

 were the same as in the previously described experiments, starting 

 with 100 mg of Enovid (50 mg/ml sesame oil) at the time of castra- 

 tion and 50 mg per injection thereafter. As shown in Table I, this 

 effectively delayed antler shedding for an average of 138 days, or 

 26 days after the final injection. However, caution is indicated in 

 concluding that these results represent solelv the effects of reduced 

 gonadotropin secretion, for in addition to the active ingredient, 17- 

 ethynyl-17-hydroxy-5( 10)-estren-3-one ( norethynodrel ) , these prep- 

 arations also contained 1.5 per cent of the 3-methyl ether of ethynyl 

 estradiol, which would be expected to mimic the effects of estrogen 

 as described above. To obviate this objection, 3 other castrated deer 

 were similarly injected with purified preparations of norethynodrel * 

 over a period of 112 days. Their antlers were retained an average of 

 39 days after the last injection (Table I), indicating the possibilitv 

 that antler shedding may be stimulated by a pituitary hormone, per- 

 haps a gonadotropin. 



The hypothesis advanced by Tachez}' (1956) that gonadotropin 

 might be responsible for the shedding if not the regrowth of antlers 



* The author is especially grateful to G. D. Searle and Co. for their cooperation 

 and generosity in supplying Eno\'id and purified samples of norethynodrel. 



