For more than a century, reproductive biology has viewed the ovary primarily through the lens of fertility. The ovary is the organ that produces oocytes, orchestrates the menstrual cycle, and secretes estrogen and progesterone to regulate reproduction. Menopause, accordingly, has been defined almost exclusively by the cessation of menstruation. This framework has served reproductive medicine remarkably well, but it has also constrained how we think about ovarian aging, women's health, and therapeutic opportunities.

It is time to adopt a broader paradigm. Rather than viewing menopause as the end of ovarian function, we should instead ask what endocrine functions the aging ovary retains, which are lost during aging, and whether those functions can be preserved or restored to improve health throughout later life. The ovary should not simply be considered a reproductive organ—it should be recognized as a lifelong endocrine organ whose biology extends far beyond estrogen production and fertility. 

Hormone replacement therapy (HRT) represents one of the greatest successes of modern women's health. For millions of women, estrogen-based therapies effectively alleviate vasomotor symptoms, preserve bone density, and improve quality of life when initiated appropriately. Yet, despite decades of clinical use, HRT has remained conceptually rooted in our understanding of ovarian biology from the early-to-mid 20th century. Current therapies primarily replace one or two steroid hormones and do so using pharmacological regimens that only loosely resemble the physiology of a functioning ovary. They neither reproduce the dynamic cyclicity of ovarian hormone production nor recapitulate the remarkable diversity of endocrine factors secreted by the ovary.

The ovary produces far more than estrogen and progesterone. It secretes androgens, inhibins, activins, follistatins, anti-Müllerian hormone (AMH), cytokines, growth factors, and numerous peptide hormones whose physiological roles remain incompletely understood. We have largely ignored this endocrine complexity because reproduction has traditionally been the primary focus of ovarian research, and women’s health is chronically underfunded. Consequently, menopause has often been interpreted simply as estrogen deficiency rather than as the loss of an entire endocrine network.

Anti-Müllerian hormone (AMH) provides an instructive example. Clinically, AMH is widely used as a biomarker of ovarian reserve because circulating concentrations decline during reproductive aging and become essentially undetectable after menopause. Yet remarkably little is known about the physiological consequences of losing AMH itself. We know that AMH receptors are expressed in numerous non-reproductive tissues, including the adrenal gland, suggesting functions beyond fertility. Preliminary studies from our laboratory suggest that replacing physiological AMH in mouse models of menopause slows aspects of adrenal aging and reduces the development of adrenal adenomas, lesions that occur disproportionately in women. These findings remain preliminary, but they illustrate a larger principle: menopause involves the disappearance of endocrine signals whose systemic functions we have barely begun to investigate.

AMH is unlikely to be unique. If the loss of a single ovarian protein hormone can produce measurable physiological consequences, one must ask what happens when levels of hundreds of ovarian-derived endocrine molecules change throughout reproductive aging. Our incomplete understanding of these molecules represents both a major gap in reproductive biology and an extraordinary therapeutic opportunity. Rather than replacing only estrogen, future therapies may seek to restore entire endocrine programs or selectively replace combinations of hormones tailored to individual physiological needs.

Achieving this vision requires a fundamental shift in how we measure ovarian aging. Today, menopause is defined retrospectively—twelve months without menstruation. While useful clinically, this definition is poorly suited for biological discovery or therapeutic development. A disease cannot be effectively prevented if it can only be diagnosed after its defining event has occurred. Drug development targeting ovarian aging therefore lacks meaningful biomarkers that capture progressive endocrine decline before symptoms emerge.

This challenge presents one of the most exciting opportunities for machine learning and systems biology. We now possess unprecedented datasets containing genomics, proteomics, metabolomics, imaging, electronic health records, and longitudinal clinical data from hundreds of thousands of women. By integrating these datasets with our expanding understanding of ovarian biology, artificial intelligence offers the possibility of constructing quantitative trajectories of ovarian aging, identifying molecular biomarkers that precede menopause by years, and predicting individual aging trajectories. Such predictive biomarkers would fundamentally transform clinical trials by enabling therapies to be evaluated based on biological aging rather than waiting years for menopause or clinical outcomes to occur.

A broader understanding of ovarian endocrinology would also reshape our understanding of sex differences in medicine. Hormonal state is one of the largest biological variables distinguishing women across the lifespan, yet it remains incompletely integrated into studies of disease susceptibility or therapeutic response. Lessons learned from menopause will likely illuminate disorders such as polycystic ovary syndrome, infertility, and premature ovarian insufficiency while also helping explain why women differ from men in susceptibility to autoimmune diseases, cardiovascular disease, and neurodegeneration. Understanding ovarian aging is therefore not merely a reproductive question; it is central to precision medicine.

Perhaps the greatest conceptual limitation of current thinking is the assumption that the postmenopausal ovary is functionally exhausted. We often imagine the aging ovary as an empty organ that has completed its purpose, or worse, as tissue whose primary clinical significance lies in its negative influence on health, contributing to “inflammaging”. Yet neither view completely reflects ovarian biology. Even at menopause, the human ovary frequently contains hundreds if not a thousand primordial follicles, more than are ever ovulated during a woman's entire reproductive lifetime. Moreover, clinical studies have long demonstrated that postmenopausal ovaries continue to produce androgens, as evidenced by declines in circulating androstenedione concentrations following oophorectomy. The ovary therefore retains follicles and endocrine activity even after menopause, which may represent a therapeutic opportunity.

Emerging evidence from our laboratory from long-term gene therapy studies with AMH in cats, originally intended to provide a non-surgical alternative to spaying to reduce shelter overpopulation, further suggests that the ovarian stroma itself can be coaxed to maintain hormonal function and may represent an underappreciated endocrine compartment. Beyond supporting follicles, stromal endocrine cells may contribute significantly to steroid and protein hormone production when follicles decline. Comparative studies further challenge prevailing assumptions. Species such as mice and cats continue to maintain ovarian endocrine function despite profound follicular depletion, implying that mammals possess adaptive mechanisms capable of sustaining hormonal homeostasis long after fertility declines. Understanding why humans, in comparison, lose this capacity so abruptly could reveal entirely new therapeutic strategies.

Our challenge, therefore, is not simply to study menopause differently, it is to redefine what menopause represents. Rather than viewing it as the inevitable collapse of ovarian function, we propose a new framework that we call "MenoGO": menopause as a dynamic endocrine transition whose trajectory can be measured, understood, and ultimately modified. This paradigm asks whether the aging ovary can be encouraged to preserve beneficial endocrine function, whether stromal endocrine cells can compensate for follicular loss, and whether lessons from comparative biology can be translated into therapies that maintain hormonal health without necessarily restoring fertility.