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Estradiol dynamics during superovulation are associated with oocyte quantity and maturation stage in cynomolgus

Hyori Lee¹, Dong-Ho Lee², Yejin Kim³

¹Primate Resources Center (PRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), Nengme-gil, Jeongeup-si, Jeollabuk-do, Republic of Korea; Department of Biological Science, College of Natural Sciences, Wonkwang University, Iksan, Republic of Korea.

|July 1, 2026

Abstract

Objective:

To examine whether dynamic changes in circulating estradiol during ovarian stimulation are associated with the number and maturation status of oocytes recovered in cynomolgus macaques.

Design:

Observational study based on retrospective analysis of ovarian stimulation cycles.

Subjects:

Sixty-six ovarian stimulation cycles from adult female cynomolgus macaques (Macaca fascicularis) housed at the Primate Resources Center.

Exposure:

Animals underwent a standardized gonadotropin-based ovarian stimulation protocol. Circulating estradiol concentrations were measured at multiple time points during the late follicular phase before oocyte recovery, and estradiol dynamics were defined as the difference between the maximum and minimum values observed across these measurements.

Main Outcome Measures:

Total number of oocytes recovered per stimulation cycle, number of mature oocytes at the metaphase two stage, and proportional distribution of oocyte maturation stages.

Results:

Dynamic changes in estradiol concentrations were positively associated with the total number of oocytes recovered per cycle (correlation coefficient 0.45). A similar but weaker association was observed with the number of mature oocytes recovered (correlation coefficient 0.36). In contrast, estradiol dynamics were not associated with the proportional distribution of oocyte maturation stages. Donor age and body weight were not significantly associated with oocyte recovery outcomes.

Conclusion:

Dynamic changes in circulating estradiol during ovarian stimulation primarily reflect the quantitative dimension of ovarian response in cynomolgus macaques, with limited relevance for the maturation stage composition of recovered oocytes.

Keywords:

Cynomolgus Macaque Estradiol Dynamics Oocyte Maturation Ovarian Response Ovarian Stimulation

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