---
title: What happens to hormones and follicles when estrogen is blocked in the menstrual cycle?
description: Blocking estrogen with antibodies increased FSH and LH hormones and caused larger follicles to grow. This was tested in monkeys, not people.
url: https://niyora.com/research/papers/passive-immunization-with-anti-oestradiol-antibodies-during-the-luteal-phase-of-1987/
---

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- What happens to hormones and follicles when estrogen is blocked in the menstrual cycle?

Survey study, 1987

# What happens to hormones and follicles when estrogen is blocked in the menstrual cycle?

Blocking estrogen with antibodies increased FSH and LH hormones and caused larger follicles to grow. This was tested in monkeys, not people.

 Early or limited evidence

3 cynomolgus monkeys with one ovary removed

## What they did

Three monkeys had one ovary removed and their cycles were driven by artificial hormone injections. During the luteal phase, researchers gave them estrogen-blocking antibodies for 7 days.

## What they found

Hormone levels (FSH and LH) increased throughout the 7-day antibody treatment. The largest follicles grew to 2.45 plus or minus 0.23 mm in treated monkeys compared to 1.30 plus or minus 0.53 mm in controls. Treated animals had 28 follicles over 1.0 mm, including 8 over 2.0 mm. Controls had only 9 follicles over 1.0 mm and none over 2.0 mm.

## What it means for you

This animal study suggests that estrogen and progesterone normally limit hormone release and follicle growth in the second half of the cycle. This is basic science that may eventually help understand how cycles work, but it has not been tested in people and is not a treatment.

3

monkeys

2.45 vs 1.30

mm largest follicle, treated vs control

28 vs 9

follicles over 1.0 mm, treated vs control

## About the study

Original title Passive immunization with anti-oestradiol antibodies during the luteal phase of the menstrual cycle potentiates the perimenstrual rise in serum gonadotrophin concentrations and stimulates follicular growth in the cynomolgus monkey (Macaca fascicularis) Authors Zeleznik AJ, Hutchinson JS, Schuler HM Journal Journal of reproduction and fertility Year 1987 Study design Survey study What was tested Estrogen-blocking antibodies for 7 days during luteal phase Open access Yes Read the paper [doi.org/10.1530/jrf.0.0800403](https://doi.org/10.1530/jrf.0.0800403)

## Topics

[Cognition, concentration and memory](https://niyora.com/research/topics/symptom-cognition/)[GnRH agonists and ovarian suppression](https://niyora.com/research/topics/treatment-gnrh/)

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