Jerilynn C. Prior BA, MD, FRCPC, Professor Emerita, Endocrinology/Medicine University of British Columbia
Polycystic Ovary Syndrome or PCOS has a new name!
At a presentation in Prague at the European Congress of Endocrinology, on May 12, 2026, Dr. Helena Teede, prominent Australian endocrinologist, announced a new name for PCOS! There was great fanfare, as Polyendocrine Metabolic Ovarian Syndrome or PMOS was announced. This was confirmed and the collaborative international methodology leading to the naming was explained in a Lancet publication about a month later 1. This well-touted, oft-tweeted PCOS-to-PMOS name change is now everywhere.
This extensive effort to rename PCOS deserves our appreciation and respect. It provided an exciting, unequaled opportunity to change our understanding of this common and often devastating condition. However, with this name change, we are abandoning ovarian cysts to emphasize the metabolic consequences of this still-mysterious, multifaceted problem.
I read the Lancet article very carefully1. The authors are to be congratulated on the complexity, the long-duration and the methodological care in the consensus-building name-changing process. There was a lot in this publication about how the 14,360 people with lived PMOS experience participated and how many dozen professionals from many countries provided input to surveys and conferences.
PMOS means ignoring ovarian cysts
What are cysts? A cyst is usually a clear, fluid-filled spherical structure. Cysts occur in many parts of the body. They sometimes occur on the face in those with severe acne (when the cysts are filled with pus). A ganglion cyst can occur on a hand, a baker’s cyst behind the knee, and a sebaceous cyst in head hair. All of these are one-off, infrequent cystic occurrences. A rare ovarian cyst will have echoes within—in that case it is urgent that ovarian cancer be excluded. Ovarian cysts, however, are fundamental to the healthy menstrual cycle.
An ovarian cyst begins as a tiny follicle, a single-layer of potentially estrogen-producing cells circling an egg. As a girl baby is born, each of her ovaries shelters about a million follicles. In an orderly fashion, follicles become larger, and develop a second theca layer as they are stimulated by brain hypothalamus and pituitary hormones. These larger ovarian cysts migrate from the centre to the outer ovary to be ready if they are called to ovulate releasing their egg.
Every few weeks normally, a bunch of these follicles are stimulated to grow and mature by the pituitary’s Follicle Stimulating Hormone (FSH). And as they do, they make more estrogen. But pituitary Luteinizing Hormone (LH) also increases in response to faster hypothalamic signals and stimulates the cysts’ outer theca layer to make testosterone. That testosterone can be converted into estrogen. The race to determine the dominant follicle is decided by the follicle that makes the most estrogen. It becomes the one destined to ovulate and release its egg.
But the hypothalamic signaling to the pituitary is sensitive to everything in the lives of that person with ovaries. If that person is abused, facing economic stress, or ill, or prevented from becoming who they dream of being, the brain-pituitary-ovary coordination is disturbed. No ovulation occurs. That anovulation leaves a cyst in the ovary.
An ovarian cyst thus means no egg release. That, in turn means that there is no progesterone production. Or, as is more common, there are some stressors and ovulation can occur. But the subsequent progesterone production is too short for optimal fertility 2 , bone formation 3, and many other key body processes 4.
Our understanding of what used to be called PCOS is poly (meaning many) ovarian cysts. They differ from cysts from usual stressors causing anovulation by being less developed. Nevertheless, cysts mean anovulation. In PCOS they make a “necklace-like” circle on the outer edge of the ovaries. These many cysts represent the long cycles in PMOS that are without egg release.
But to see ovarian cysts requires either some kind of surgery or an ultrasound, a costly and sometimes difficult-to-schedule medical investigation. Even then, it is not easy to tell apart these so-called PCOS-like cysts from the odd or multiple ovarian cysts that occur with hypothalamic stress-related anovulation 5. Multiple ovarian cysts commonly occur in teens as their hypothalamic-pituitary-ovarian system is still learning to normally ovulate. This is also when PCOS/PMOS is first diagnosed.
It is a good idea to get rid of cysts from the PCOS name since it made folks think an ultrasound was necessary. Furthermore, people who had ovarian cysts, even though their cause was hypothalamic stress interfering with ovulation, often got mistakenly diagnosed with PCOS 6.
However, we need to learn and accept what ovarian cysts were trying to tell us. In what we now call PMOS, cysts mean that there is plenty of estrogen yet little or no progesterone. Without progesterone, the hypothalamus signals to the pituitary to stay rapidly pulsing, LH continues to be the most active, and it leads to lower FSH, fewer follicles maturing, incoordination, longer cycles and lack of ovulation. This lack of cyclic progesterone creates a forever repeating, unhealthy or vicious cycle.
But I didn’t understand any of that when I first started seeing patients as the only woman in endocrinology in Vancouver in 1979.
What two things did my first Vancouver patients share?
My first referred patients had either PCOS or hirsutism with regular cycles. They shared two things: hirsutism (unwanted, beard-like, facial hair), and hatred of the birth control pill!
I was referred young women who were considered “problem patients” that no other specialists wanted to see. They couldn’t get anyone to listen when they said that the Pill didn’t help. In fact, the Pill made them feel bloated and gain weight, depressed, and not like themselves. On the Pill, those with PCOS sometimes got regular periods, but weight and facial hair did not importantly improve 7.
In those early years I was keen to build a reputation as a good doctor. Yet I had no clue how to treat the women referred to me. I was well trained in clinical endocrinology. But women’s menstrual cycles and reproduction were solely managed by gynecology. Endocrinologists didn’t interfere.
I understood why these first patients of mine did not want to take the Pill. I had tried one of the early Pills in the 1960s that had 100 micrograms of estrogen (versus today’s 15-20). I only lasted five days! I stopped it because of severe swelling, my first migraine and almost cancelling my wedding. As a medical student, despite being desperate to prevent pregnancy, I could not take the Pill 8.
How could I helpfully treat my new PCOS patients? I went to the medical library. There I found a 1957 study showing, in a series of young women with PCOS, that over a third developed endometrial cancer (malignancy in the lining of the uterus) 9.
Endometrial cancer had recently been in the news. Like all physicians, I knew about it. In 1975, in a horrifying revelation, we learned that menopausal estrogen treatment was associated with an increased risk for endometrial cancer. This lining-of-the-uterus cancer occurred in menopausal woman taking estrogen as the candy-coated red PremarinÒ pills (a pregnant mare’s urine-based estrogen) that doctors were delighted to prescribe.
However, we soon learned that progestin treatment could prevent endometrial cancer in estrogen-taking menopausal women. A progestin is a synthetic drug that works like progesterone in the uterus. Estrogen could still be used to treat menopause as long as a progestin (or later progesterone) was also prescribed for someone with a uterus.With the knowledge that those with PCOS were at increased risk of both long cycles and endometrial cancer, I had a bright idea:
What if I were to prescribe progestin?
AND, instead of giving it daily as in menopause, or with estrogen, I would give the progestin for 14 days each month, like the optimal progesterone-producing part of the menstrual cycle (luteal phase) following ovulation. It should create regular periods and prevent endometrial cancer.
I told my new PCOS patients my idea. Would they be willing to try 14 days/month of progestin?
They were willing, and did. To cut a long story short, most of my new patients with PCOS were treated with a progestin for 14 days a month. And, after 1996, when oral micronized progesterone became available as a Health Canada approved medicine, I prescribed Cyclic Progesterone Therapy instead.
My PCOS patients reported spotting and inconsistent bleeding for the first few cycles. But, despite that, and the inconvenience of more frequent flow, they reported feeling better. When they returned to see me, they stood taller. I could see it was a remarkable change they felt. But at the time, I couldn’t explain it.
Later I learned that progesterone talks back to the hypothalamus, slows its commonly too-fast pulses and is essential for healthy menstrual cycle. Progesterone was slowing more rapid LH pulses and encouraging ovulation 10, 11. I had accidentally learned why ovarian cysts in PCOS are important. PCOS cysts told us that these people with ovaries were lacking ovulation and progesterone.
Does PMOS fundamentally change concepts?
Dr. Teede and colleagues set out to change the name of PCOS, as others had encouraged years before 12. At that time, colleagues and I responded with a Letter to the Editor saying that we should call PCOS, “Anovulatory Androgen Excess” (or AAE) 13. This name identified the importance of not ovulating and of making too much male hormone.
What was the goal of the PCOS-to–PMOS name change?
According to the Lancet article, what those with a lived experience of the condition wanted was less stigma from the PCOS name. What scientists and clinicians wanted was more diagnostic accuracy and increased recognition that insulin resistance, obesity, diabetes, cardiovascular and liver problems are PCOS-related.
Yet the words, “ovulation” and “progesterone” were totally absent from this document 1. In addition, I found nothing concrete about treatment—“the Pill” and “combined hormonal contraception” were also not mentioned 1.
However, for PMOS, according to the latest guidelines, the Pill, that my patients hated in 1979, remains the primary, authorized therapy 14.
This name-change feels like a huge lost opportunity. In this admirable and important endeavour that generated PMOS, the investigators and those with lived experience have NOT transformed our fundamental understanding of this condition suffered by one in eight reproductive-aged people with ovaries.
What I have learned from my many patients and research participants living with this condition is, that by any name, PCOS-to-PMOS can virtually be cured by cyclic progesterone therapy.
Reference List
- Teede HJ, Khomami MB, Morman R, et al. Polyendocrine metabolic ovarian syndrome, the new name for polycystic ovary syndrome: a multistep global consensus process. Lancet 2026 20260512. DOI: 10.1016/S0140-6736(26)00717-8.
- Crawford NM, Pritchard DA, Herring AH, et al. Prospective evaluation of luteal phase length and natural fertility. Fertil Steril 2017; 107: 749-755. S0015-0282(16)63022-4 pii ;10.1016/j.fertnstert.2016.11.022 doi.
- Prior JC. Progesterone as a bone-trophic hormone. Endocrine Reviews 1990; 11: 386-398.
- Prior JC and Vitzthum VJ. Progesterone for reproductive vitality and women’s healthy ageing. Exploration of Endocrine and Metabolic Diseases 2026; 3. DOI: 10.37349/eemd.2026.101460.
- Prior JC. Adaptive, reversible, hypothalamic reproductive suppression: More than functional hypothalamic amenorrhea. Frontiers in Endocrinology 2022; 13. DOI: 10.3389/fendo.2022.893889.
- The Rotterdam EA-SPCWG. Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome. Fertil Steril 2004; 81: 19-25. S001502820302853X pii.
- Teede H, Tassone EC, Piltonen T, et al. Effect of the combined oral contraceptive pill and/or metformin in the management of polycystic ovary syndrome: A systematic review with meta-analyses. Clin Endocrinol (Oxf) 2019; 91: 479-489. 2019/05/16. DOI: 10.1111/cen.14013.
- Prior JC. Apply the Precautionary Principle Concerning Combined Hormonal Contraception Use in Adolescents. Women’s Reproductive Health 2016; 3: 113-116.
- Jackson RL and Dockerty MB. The Stein-Leventhal syndrome: analysis of 43 cases with special reference to association with endmetrial carcinoma. Am j obst & gynec 1957; 73: 163-173.
- Prior JC. The case for a new PCOS therapy. I’ve been treating patients with PCOS for 40 years. Here is my approach. https://hellocluecom/articles/cycle-a-z/the-case-for-a-new-pcos-therapy 2018.
- Briden L, Shirin S and Prior JC. The central role of ovulatory disturbances in the etiology of androgenic polycystic ovary syndrome (PCOS)—Evidence for treatment with cyclic progesterone. Drug Discovery Today: Disease Models (Part B) 2020; 32: 71-82. DOI: https://doi.org/10.1016/j.ddmod.2020.11.008.
- Azziz R. Polycystic ovary syndrome: what’s in a name? J Clin EndocrinolMetab 2014; 99: 1142-1145. 10.1210/jc.2013-3996 doi.
- Prior JC, Kalyan S and Seifert-Klauss V. Re-naming pcos – suggest anovulatory androgen excess. 2016.
- Teede HJ, Tay CT, Laven JJE, et al. Recommendations from the 2023 international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Eur J Endocrinol 2023; 189: G43-G64. DOI: 10.1093/ejendo/lvad096.