Negative impact of high doses of follicle-stimulating hormone during superovulation on the ovulatory follicle function in small ovarian reserve dairy heifers†.

When women with small ovarian reserves are subjected to assisted reproductive technologies, high doses of gonadotropins are linked to high oocyte and embryo wastage and low live birth rates. We hypothesized that excessive follicle-stimulating hormone (FSH) doses during superovulation are detrimental to ovulatory follicle function in individuals with a small ovarian reserve. To test this hypothesis, heifers with small ovarian reserves were injected twice daily for 4 days, beginning on Day 1 of the estrous cycle with 35, 70, 140, or 210 IU doses of Folltropin-V (FSH). Each heifer (n = 8) was superovulated using a Williams Latin Square Design. During each superovulation regimen, three prostaglandin F2α injections were given at 12-h interval, starting at the seventh FSH injection to regress the newly formed corpus luteum (CL). Human chorionic gonadotropin was injected 12 h after the last (8th) FSH injection to induce ovulation. Daily ultrasonography and blood sampling were used to determine the number and size of follicles and corpora lutea, uterine thickness, and circulating concentrations of estradiol, progesterone, and anti-Müllerian hormone (AMH). The highest doses of FSH did not increase AMH, progesterone, number of ovulatory-size follicles, uterine thickness, or number of CL. However, estradiol production and ovulation rate were lower for heifers given high FSH doses compared to lower doses, indicating detrimental effects on ovulatory follicle function.