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Study on the Effects of Letrozole in Reducing Ovarian Volume in Women Undergoing Controlled Ovarian Stimulation for Egg Donation

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying the effects of a medication called letrozole in women who are participating as oocyte donors. The study is particularly interested in understanding how letrozole affects the ovaries during a specific time in the menstrual cycle known as the luteal phase, which occurs after the ovaries have been stimulated to produce eggs. The main goal is to see if using letrozole can reduce the size of the ovaries during this phase.

The study involves women who are part of an oocyte donation program and are between the ages of 18 and 34. These women have shown a strong response to ovarian stimulation, which means they have developed a significant number of follicles, or small sacs in the ovaries, that contain eggs. The trial is designed to be low-interventional, meaning it aims to minimize any additional procedures or risks for the participants.

Participants in the study will be randomly assigned to receive either letrozole or a placebo. The researchers will monitor the size of the ovaries and measure various hormone levels in the blood, such as oestradiol, progesterone, and testosterone, to gather information on how letrozole affects these factors. The study is expected to continue until August 2025, providing valuable insights into the potential benefits of using letrozole in this context.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, you will be informed about the purpose and procedures involved. You will be required to provide a dated and signed informed consent, confirming your understanding and agreement to participate.

  2. Step 2

    Initial assessment

    An initial assessment will be conducted to confirm your eligibility. This includes verifying that you are a woman aged between 18 and 34 years, accepted into the oocyte donation program, and have shown hyperresponsiveness to stimulation, defined as having 18 or more follicles of size 11 mm or larger on the day of the last ultrasound control visit before ovarian puncture.

  3. Step 3

    Medication administration

    You will be administered letrozole, which is taken orally. The specific dosage, frequency, and duration of administration will be provided to you by the study team. This medication is used during the luteal phase, which is the period after ovulation, to assess its effects on ovarian volume.

  4. Step 4

    Monitoring and follow-up

    Throughout the study, regular monitoring will be conducted to assess the effects of the medication. This includes measuring ovarian volume and checking plasma values of certain hormones and proteins, such as VEGF, sFlt-1, oestradiol, progesterone, FSH, LH, and testosterone.

  5. Step 5

    Completion of the study

    Upon completion of the study, a final assessment will be conducted to evaluate the outcomes. You will be informed about the results and any further steps, if necessary.

Who can join the trial?

4 criteria

  • Must be a woman who is part of the IVI's oocyte (egg) donation program.
  • Age must be between 18 and 34 years old.
  • Must show hyperresponsiveness to stimulation, which means having at least 18 follicles that are each 11 mm or larger on the day of the last ultrasound before the egg retrieval procedure. Follicles are small sacs in the ovaries where eggs develop.
  • Must have given dated and signed informed consent, which means you understand the study and agree to participate.

Who cannot join the trial?

8 criteria

  • Participants must not have any other medical conditions that could interfere with the study.
  • Participants must not be taking any medications that could affect the study results.
  • Participants must not have a history of allergic reactions to the study medication.
  • Participants must not be pregnant or breastfeeding.
  • Participants must not have participated in another clinical trial recently.
  • Participants must not have any significant health issues that could pose a risk during the study.
  • Participants must not have a history of substance abuse.
  • Participants must not have any mental health conditions that could affect their ability to participate.
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Investigated drugs

Letrozole is a medication used in this clinical trial to see if it can reduce the size of the ovaries in women who donate eggs. It works by lowering the levels of estrogen, a hormone that can affect the ovaries. In this study, letrozole is given during a specific time in the menstrual cycle, called the luteal phase, after the ovaries have been stimulated to produce eggs. The goal is to find out if letrozole can help manage the changes in the ovaries that happen after this stimulation process.

What is already known about the treatment

Letrozole – Letrozole is taken orally in the form of a tablet. It is currently being studied in clinical trials for its effects on female infertility, specifically in oocyte donors. The main therapeutic use of letrozole is to help with fertility by stimulating the ovaries. It works by blocking an enzyme called aromatase, which reduces estrogen levels and encourages the ovaries to produce more eggs. Letrozole is classified as an aromatase inhibitor in pharmacology.

Investigated diseases

Female Infertility – Female infertility is a condition where a woman is unable to conceive after a year of regular, unprotected sexual intercourse. It can result from various factors affecting the reproductive system, including hormonal imbalances, structural issues, or problems with ovulation. The progression of female infertility can vary depending on the underlying cause. Hormonal imbalances may lead to irregular menstrual cycles or anovulation, where no egg is released. Structural issues, such as blocked fallopian tubes or uterine abnormalities, can prevent the sperm from reaching the egg or the fertilized egg from implanting. Over time, these factors can contribute to ongoing difficulties in achieving pregnancy.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2022-502586-21-00Protocol code2206-MAD-089-SCEstimated enrolment152 patientsSponsorIvi Madrid S.L.

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