Livio Casarini, Alberto Vaiarelli, Danilo Cimadomo, Daniele Santi, Manuela Simoni, Juan Antonio Garcìa-Velasco, Carlo Alviggi, Antonio La Marca, Laura Rienzi, Filippo Maria Ubaldi

    Human Reproduction, Letter to the editor, pp. 1-2, 2022 – deac064 https://doi.org/10.1093/humrep/deac064 – Published: 08 April 2022



    We have carefully read the opinion paper published by Dr Angelo Tocci about the hypothetical mechanism explaining the effectiveness of double stimulation in the same ovarian cycle (DuoStim) (Tocci, 2022). Tocci (2022) suggests that the higher oocyte number generally collected after the second stimulation is imputable to differentiation of two FSH-responsive stem cell populations, i.e. very small embryonic-like and human ovarian stem cells (OSCs), presumably present in the ovarian surface epithelium (OSE). The opinion viewpoint is that the first stimulation may trigger the commitment of oocyte progenitors to differentiate into mature oocytes. We certainly recognize the author’s efforts in explaining how anovulatory waves of follicle growth may result in oocytes like those collected after the first stimulation per embryological, clinical and perinatal outcomes (Vaiarelli et al., 2020). On the contrary, strong concerns arose about the misleading inference that a second stimulation is ‘potentially unsafe’….