Effects of Letrozole During the Luteal Phase After Controlled Ovarian Stimulation in Oocyte Donors.

Clinical and Endocrinological Effects of Letrozole During the Luteal Phase After Controlled Ovarian Stimulation in Oocyte Donors: a Low Interventional, Randomized, Controlled Trial

The objective of this trial is to determine whether the use of letrozole during the luteal phase in oocyte donors diminishes the ovarian volume, as well as to evaluate its effect on the duration of the luteal phase, taking into account hormonal and biochemical markers.

Two groups will be established with random allocation of patients and 1:1 proportionality, as follows:

• Control group: No specific treatment.
• Study group: Oral administration of letrozole 5 mg (each capsule is 2.5 mg) once a day for 5 days starting on the night of the follicular puncture.

Letrozole is a widely used drug in the context of hormone-dependent malignant tumors due to its antiestrogenic effect. Its mechanism of action allows its application to the field of Assisted Reproductive Medicine, mainly as an inductor of ovulation, by means of a blockage in the negative feedback signalization of the hypothalamus-pituitary-gonadal axis. In the last years, it has also been tested with the goals of preventing ovarian hyperstimulation syndrome (OHSS) or analyzing its effects on several endocrinological and biochemical markers such as LH, progesterone or VEGF. However, the results are inconsistent on every account. Data regarding the effect on ovarian size and the duration of the luteal phase following the administration of letrozole after the oocyte pick-up can be useful to evaluate the benefit of this drug in patients with a tendency towards hyperresponse, in which both the discomfort after the stimulation and the risk of ovarian torsion are increased.

The objective of this trial is to determine whether the use of letrozole during the luteal phase in oocyte donors diminishes the ovarian volume, as well as to evaluate its effect on the duration of the luteal phase, taking into account hormonal and biochemical markers

Inclusion Criteria:

• Hyper-responsiveness to stimulation, defined as the presence of ≥18 follicles of size ≥11 mm (22-24) on the day of the last ultrasound visit prior to ovarian puncture.

Exclusion Criteria:

• Participation in another clinical study, prior to inclusion in the present study, that could affect the objectives of this study.
• Known allergy to letrozole.
• Known lactose intolerance.