Follicular steroidogenesis in random start protocols for oocyte cryopreservation

PURPOSE: Random start protocols are commonly used for oocyte cryopreservation in women with cancer. However, albeit generally reassuring, available evidence is still insufficient to rule out a sub-optimal cycle outcome. This study aimed to compare follicular steroidogenesis between women initiating the random start protocol in the luteal phase and those initiating in the follicular phase. METHODS: Consecutive women with cancer scheduled for oocyte cryostorage were prospectively recruited. We excluded those requiring a concomitant letrozole assumption. All women received a standardized protocol with recombinant FSH and GnRH antagonists. At the time of oocyte retrieval, follicular fluids were pooled, and a sample was collected and frozen at −80 °C. All samples were assayed concomitantly after thawing by liquid chromatography-tandem mass spectrometry. The concentration of 15 different steroid hormones was determined. RESULTS: Seventy-one women were recruited. Thirty-three initiated the ovarian stimulation in the luteal phase, while the remaining 38 initiated in the follicular phase. Baseline characteristics were generally similar. Cycle outcome did also not differ; the median (interquartile range) number of frozen mature oocytes was 9 (5–14) and 10 (5–21), respectively (p = 0.42). None of the 15 tested steroid hormones differed. CONCLUSIONS: The endocrine microenvironment surrounding oocytes is not markedly influenced by the phase of the menstrual cycle at the initiation of ovarian stimulation. This result further supports the validity of random start protocols. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10815-023-02883-z.