Abstract
The minimum dose of human chorionic gonadotrophin needed to induce ovulation was determined in hamsters, in which the luteinizing hormone surge was blocked by administration of phenobarbitone. Doses of 1.0, 2.5, 5.0 and 10.0 IU human chorionic gonadotrophin were injected subcutaneously, and 5.0 IU was found to be the minimum dose needed to induce ovulation in all of a group of seven hamsters. When this minimum dose was used to induce ovulation repeatedly, one, two or three times, in groups of seven hamsters the percentages of abnormal eggs seen were 5.3%, 5.6% and 6.4%, respectively. These results indicate that the marked increases in the proportions of abnormal eggs produced when ovulation is repeatedly induced, which have been observed in previous studies, can be prevented by using the minimum effective dose of human chorionic gonadotrophin.