Abstract
SUMMARY: Cyclopentyl enol ethers of some orally active progestational steroids have been compared with their parent compounds for their ability to inhibit hypersecretion of pituitary gonadotrophin in parabiotic rats (intact female—castrated male). Although in previous experiments enolic etherification altered the 'antioestrus' activity it did not change the antigonadotrophic potency either of 6α-methyl-17α-acetoxyprogesterone or 17α-ethynyl-19-nortestosterone acetate. The lack of parallelism between antigonadotrophic and 'antioestrus' activities is discussed.