For most women, the body begins to change dramatically in their 40s or 50s. This transition, known as menopause, is defined as 12 consecutive months without a menstrual period, marking the end of the reproductive years. While researchers are aware of the functions the ovaries perform during active reproductive years, what happens to the organ after menopause is largely a mystery.
A recent study in Molecular Human Reproduction investigated what happens to the ovary in mice after it stops producing eggs, a period known as the post-reproductive stage, similar to menopause in humans.
Researchers found that even after the ovary can no longer support reproduction, it doesn’t simply become inactive. Instead, aging ovaries undergo remarkable changes, producing a different set of signaling molecules from those of younger ovaries.
In doing so, the ovary shifts away from its reproductive role and transforms into an organ that assumes immune functions, participating in processes such as inflammatory signaling and leukocyte activation.
What comes after eggs?
Ovaries change throughout a woman’s life, from producing immature eggs at birth to releasing mature eggs during the reproductive years, then shrinking in size and function after menopause. Women are born with a fixed, limited supply of follicles—small sacs holding immature eggs—and that supply steadily shrinks with age.
The ovary ages decades before any other organ in the body, showing up as a drop in both the number and quality of follicles. By menopause, only about 1,000 follicles remain.
Due to advances in medical science, humans live much longer than they did a century ago. Yet surprisingly little is known about what the ovaries do after menopause.
Studying human ovaries is challenging because access to samples is limited. To help answer that question, researchers turned to mice, as their ovaries follow a similar pattern of aging: Fertility declines before they enter a post-reproductive stage known as oopause.
To find out how the ovary changes after it can no longer produce eggs, researchers studied mice at different stages of life, creating a timeline of ovarian aging. They selected three groups of mice: reproductively young (2 months old), reproductively old (18 months old) and post-reproductive (24 months old, which is past when they hit oopause).
One ovary from each pair was used to study the physical structure, and the other was used to study its genetic activity via transcriptomics. This allowed researchers to see whether the post-reproductive ovary was still functioning and what its cells were doing. They then used existing data sets to identify which of these active genes produced molecules that could signal to other parts of the body.
An ovary remade by inflammation
They found that by the time mice reached the post-reproductive stage, they had completely run out of follicles, and the ovaries became much stiffer due to a significant increase in collagen. Even after follicle loss leveled off, the ovaries kept changing at the molecular level. Researchers discovered an influx of immune cells in the organ.
The aging ovaries were packed with T cells, macrophages and large giant cells, indicating a shift from a primarily reproductive state to one dominated by the immune system.
While the genes responsible for egg production and reproductive hormone synthesis were mostly turned off, those related to inflammation, immune responses and white blood cell activation were aggressively turned on. They also found that these newly transformed ovaries send out chemical signals that travel through the bloodstream.
The researchers said these findings challenge the idea that the post-reproductive ovary is inactive. Instead, they suggest it takes on an immune-like role, with the potential to influence aging throughout the body through pro-inflammatory signaling.
Future studies confirming similar changes in human ovaries could open the door to new ways to improve the lives of millions of postmenopausal women by targeting ovarian inflammation to reduce the risk of inflammatory and age-related diseases. https://medicalxpress.com/news/2026-07-ovaries-job-immune-tenure-reproductive.html
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