Serum FSH Levels During Controlled Ovarian Stimulation

Follicle-stimulating hormone (FSH) plays a central role in controlled ovarian stimulation (COS) during in vitro fertilization (IVF) cycles. While baseline FSH is commonly used to assess ovarian reserve, the clinical significance of dynamic FSH changes during stimulation remains unclear. Limited evidence suggests that serum FSH levels during COS may reflect ovarian response and could be associated with follicular development and treatment outcomes, yet FSH is not routinely monitored throughout stimulation protocols.

This prospective single-center cohort study aims to evaluate the dynamics of serum FSH levels during COS and to examine their association with ovarian response and IVF outcomes. Serum FSH, luteinizing hormone (LH) and estradiol (E2) will be measured at predefined time points during stimulation. Associations between FSH levels and oocyte yield, embryo development, and pregnancy outcomes will be analyzed to better understand the clinical relevance of FSH monitoring during IVF treatment.

Study Overview

• Status: Not yet recruiting
• Conditions: Female Subjects Undergoing Controlled Ovarian Hyperstimulation

Detailed Description

Background and Rationale

Follicle-stimulating hormone (FSH), secreted by the anterior pituitary gland in response to gonadotropin-releasing hormone (GnRH), plays a critical role in ovarian follicular development and estradiol production. In assisted reproductive technologies (ART), exogenous FSH is administered during controlled ovarian stimulation (COS) to promote multifollicular growth. Although baseline FSH is widely used as a marker of ovarian reserve and predictor of ovarian response, the clinical significance of dynamic FSH changes during stimulation remains insufficiently characterized.

Day 7 of stimulation represents a clinically important time point during which follicular growth and synchronization are assessed. Prior studies have suggested that serum FSH levels during COS may correlate with ovarian response and may reflect an individualized FSH threshold beyond which increasing exogenous dosing may not improve follicular recruitment. However, consensus is lacking regarding the clinical utility of serial FSH monitoring during stimulation, and it is not routinely incorporated into IVF protocols.

Understanding the relationship between FSH dynamics, follicular development, estradiol production, and treatment outcomes may support more individualized stimulation strategies and improve reproductive outcomes.

Study Design

This is a prospective observational cohort study conducted at a single academic fertility center at the McGill University Health Centre (MUHC) Reproductive Centre.

Study Population

Eligible participants include patients undergoing controlled ovarian stimulation for IVF or ICSI at the MUHC Reproductive Centre. All stimulation protocols (GnRH agonist and antagonist) and all gonadotropin formulations (including Gonal-F, Menopur, Rekovelle, and Puregon) are included.

Data Collection

Demographic and clinical data will include age, body mass index (BMI), obstetric history, indication for treatment, and stimulation protocol details.

Serum hormone levels of will be measured at three predefined time points:

1. Baseline (cycle day 3)
2. Day 7 or 8 of gonadotropin stimulation
3. Trigger day (day of trigger shot before oocyte retrieval)

Blood samples will be collected at time points that coincide with routine visits for women undergoing ovarian stimulation, during which blood tests are already performed as part of standard clinical care

The hormones measured include:

Serum Follicle-stimulating hormone (FSH) (mIU/mL) Luteinizing hormone (LH) (mIU/mL) Estradiol (E2) (pmol/L) Anti-Müllerian Hormone (AMH) (ng/mL)

• Study Type: Observational
• Enrollment (Estimated): 500

Contacts and Locations

Study Locations

• Canada
  • Quebec
    • Montreal, Quebec, Canada, H2L 4S8
      • MUHC Reproductive Centre

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Study will include patients undergoing controlled ovarian stimulation at the MUHC Reproductive Center. Nursing and medical team will recruit patients on their initial visit when they get their treatment plan and prescription at the MUHC Reproductive Center.

Description

Inclusion Criteria:

• Patients undergoing controlled ovarian stimulation
• All stimulation protocols (agonist and antagonist).
• All gonadotropin formulation (Gonal-F, Menopur, Rekovelle, Puregon).

Exclusion Criteria:

• Cancer fertility preservation patients .
• Patients over age 44.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Stimulation patients; Patients undergoing controlled ovarian stimulation at the MUHC Reproductive Center.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
-Trigger day FSH levels	Serum Follicle-stimulating hormone (FSH) (mIU/mL) measured at the day of the trigger shot	60 months
Trigger day E2 levels	Serum Estradiol (E2) (pg/mL) levels measured at trigger shot day	60 months
Number of patients reaching trigger	The number of patients that received the trigger shot and proceeding to oocyte retrieval / The number pf patients canceled during the ovarian stimulation	60 months
Number of oocytes retrieved	The number of oocytes collected in the oocyte retrieval procedure	60 months
Number of transferable embryos	Number of embryos were transferred in the fresh cycle plus the number of frozen embryos	60 months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Biochemical pregnancy rate	Positive pregnancy test (i.e positive serum HCG level >20 U/L after 11 days of ET of D5 embryo and 13 after D3 embryo transfer) per transfer	60 months
Clinical pregnancy rate	Pregnancy diagnosed by ultrasound with at least one embryo and a discernable heartbeat per transfer	60 months
Miscarriage rate	Spontaneous loss of clinical pregnancy before 12 weeks per transfer	60 months

Collaborators and Investigators

• Sponsor: McGill University Health Centre/Research Institute of the McGill University Health Centre

Publications and helpful links

General Publications

• Sun PP, Zhang YM, Zhu HY, Sun N, Ma HG. The relationship between serum FSH level and ovarian response during controlled ovarian stimulation. Ginekol Pol. 2023;94(6):470-475. doi: 10.5603/GP.a2022.0010. Epub 2022 Apr 14.
• de Koning CH, Schoemaker J, Lambalk CB. Estimation of the follicle-stimulating hormone (FSH) threshold for initiating the final stages of follicular development in women with elevated FSH levels in the early follicular phase. Fertil Steril. 2004 Sep;82(3):650-3. doi: 10.1016/j.fertnstert.2004.01.043.
• Bentov Y, Burstein E, Firestone C, Firestone R, Esfandiari N, Casper RF. Can cycle day 7 FSH concentration during controlled ovarian stimulation be used to guide FSH dosing for in vitro fertilization? Reprod Biol Endocrinol. 2013 Feb 22;11:12. doi: 10.1186/1477-7827-11-12.
• Abdalla H, Thum MY. An elevated basal FSH reflects a quantitative rather than qualitative decline of the ovarian reserve. Hum Reprod. 2004 Apr;19(4):893-8. doi: 10.1093/humrep/deh141. Epub 2004 Mar 11.

Study record dates

Study Major Dates

• Study Start (Estimated): February 16, 2026
• Primary Completion (Estimated): December 1, 2030
• Study Completion (Estimated): December 1, 2030

Study Registration Dates

• First Submitted: February 13, 2026
• First Submitted That Met QC Criteria: March 9, 2026
• First Posted (Actual): March 10, 2026

Study Record Updates

• Last Update Posted (Actual): March 10, 2026
• Last Update Submitted That Met QC Criteria: March 9, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Keywords: IVF; FSH; Controlled ovarian hyperstimulation; Infertiltiy
• Other Study ID Numbers: 2026-11743

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No