Progesterone and 17-hydroxy-progesterone concentrations in follicular fluid and serum reflect their production in granulosa and theca cells.

Research Question: How is the production of progesterone (P) and 17-hydroxy-P (17-OH-P) regulated between theca cells and granulosa cells during the follicular phase, during ovulation and after transformation into a corpus luteum?

Design: Three cohorts were examined: (i) 31 women undergoing natural and stimulated cycles, with serum hormone measurements taken every 3 days; (ii) 50 women undergoing ovarian stimulation, with hormone concentrations in serum and follicular fluid assessed at five time points during final follicle maturation; and (iii) 12 women undergoing fertility preservation, with hormone concentrations evaluated via the follicular fluid of small antral follicles.

Results: In the early follicular phase, theca cells primarily synthesized 17-OH-P while granulosa cells produced limited P, maintaining the P:17-OH-P ratio <1. As follicles reached follicle selection at a diameter of approximately 10 mm, P synthesis in granulosa cells was up-regulated, but P was mainly accumulated in follicular fluid.

Impact of letrozole co-treatment during ovarian stimulation on oocyte yield, embryo development, and live birth rate in women with normal ovarian reserve: secondary outcomes from the RIOT trial.

Study Question: Does letrozole (LZ) co-treatment during ovarian stimulation with gonadotropins for in IVF impact follicle recruitment, oocyte number and quality, embryo quality, or live birth rate (LBR)?

Summary Answer: No impact of LZ was found in follicle recruitment, number of oocytes, quality of embryos, or LBR.

What Is Known Already: Multi-follicle stimulation for IVF produces supra-physiological oestradiol levels. LZ is an aromatase inhibitor that lowers serum oestradiol thus reducing negative feedback and increasing the endogenous gonadotropins in both the follicular and the luteal phases, effectively normalizing the endocrine milieu during IVF treatment.

The Impact of Suppressing Estradiol During Ovarian Stimulation on the Unsupported Luteal Phase: A Randomized Controlled Trial.

Context: Supraphysiological sex steroid levels at the follicular-luteal phase transition are implicated as the primary cause of luteal insufficiency after ovarian stimulation (OS) for in vitro fertilization.

Objective: We aimed to determine the impact of suppressing estradiol levels during OS of multiple dominant follicles on the unsupported luteal phase and markers of endometrial maturation.

Methods: At 2 university hospitals, 25 eligible egg donors were randomized to undergo OS using exogenous gonadotropins with or without adjuvant letrozole 5 mg/day.

Effects of letrozole cotreatment on endocrinology and follicle development in women undergoing ovarian stimulation in an antagonist protocol.

Study Question: What are the downstream endocrine and paracrine consequences of letrozole (LZ) cotreatment during ovarian stimulation and is follicle growth and recruitment affected?

Summary Answer: Letrozole cotreatment induces marked changes in both the follicular and luteal phase endocrinology causing potentiation of follicle diameter and an improved corpus luteum function without affecting the secondarily recruited follicle cohort.

What Is Known Already: Letrozole is a third-generation aromatase inhibitor that is well-established as an effective ovulatory agent, while its possible benefits in standard in vitro fertilization protocols are less thoroughly investigated.

Study Design, Size, Duration: This study included a double-blinded, placebo-controlled, randomized study with LZ or placebo intervention during ovarian stimulation for IVF treatment, an observational preceding baseline natural cycle and a succeeding follow-up visit.