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PCOS, PMOS, Endometriosis, Adenomyosis: A Plain-English Comparison

A flat-vector diagram of five overlapping pastel circles representing the multi-system nature of PMOS and related conditions, on a soft lavender background

2026 has been a year of medical relabeling for women's health. In February, ACOG redefined what it takes to diagnose endometriosis. In May, an international consensus renamed PCOS to PMOS (polyendocrine metabolic ovarian syndrome). At the same time, adenomyosis is finally being separated from its decades-long lumping with endometriosis.

Four conditions, all involving the menstrual cycle, all routinely confused with each other and with "just bad periods." Here's how to tell them apart in plain English - including which symptoms map to which condition and which free tool to start with.

The four at a glance

| | Pain | Cycle | Bleeding | Fertility | |---|---|---|---|---| | PMOS (formerly PCOS) | Not dominant | Irregular | Light or skipped | Often reduced | | Endometriosis | Dominant, cyclical | Usually regular | Often heavy | Often reduced | | Adenomyosis | Severe, paired with bleeding | Usually regular | Very heavy | Sometimes affected | | Primary dysmenorrhea | Moderate, period-only | Regular | Normal | Not affected |

If you remember nothing else: PMOS shows up in the absence of periods, endometriosis shows up in pain between or beyond periods, adenomyosis shows up in extremely heavy painful periods, and primary dysmenorrhea is "regular bad cramps that respond to ibuprofen."

PMOS (formerly PCOS)

The endocrine and metabolic one.

In May 2026, an international consensus led by Monash University renamed PCOS to PMOS - polyendocrine metabolic ovarian syndrome - to capture how the condition actually works: a multi-system syndrome involving androgens, insulin, and ovulation, with the ovary as one piece of a larger picture.

Hallmarks:

Pain is not a hallmark. If your cycle is irregular and your dominant symptoms are skin, hair, weight, or fertility-related, PMOS is the first thing to consider. See our deeper coverage in PCOS has a new name: what 'PMOS' means and why it matters, and run the free PCOS Symptom Checker before your visit.

Endometriosis

The cyclical-pain one.

Endometriosis is when tissue similar to the uterine lining grows outside the uterus - on ovaries, fallopian tubes, bowel, bladder, pelvic walls. That tissue bleeds with your cycle but has nowhere to go, causing inflammation, scarring, and pain that often does not match what's visible on ultrasound.

Hallmarks (ACOG's February 2026 criteria):

Cycles are usually regular - it's the pain that defines endo, plus pain in places the uterus isn't (bowel, bladder, deep pelvic, lower back). The full breakdown is in our 2026 ACOG endometriosis article, and the symptom-vs-just-bad-periods comparison in period pain vs endometriosis pain. Start with the Endometriosis Symptom Checker.

Adenomyosis

The heavy-bleeding-and-pain one.

Adenomyosis is what happens when endometrial-like tissue grows into the muscular wall of the uterus rather than outside it. It's often called the "sister condition" to endometriosis, and the two coexist in roughly a third of cases - but they cause different problems.

Hallmarks:

Most useful diagnostic feature: severe pain AND extreme bleeding in the same person. Endometriosis can cause heavy periods, but pain is the dominant complaint. Adenomyosis usually presents with both equally.

Adenomyosis can be visualized on MRI and increasingly on detailed transvaginal ultrasound. Treatment overlaps with endometriosis (hormonal suppression, levonorgestrel IUD), with hysterectomy as the definitive option for those done with childbearing.

Primary dysmenorrhea ("just bad periods")

The "this is annoying but normal" one.

Primary dysmenorrhea is painful periods without an underlying structural cause. It's caused by prostaglandins - inflammation that makes the uterus contract.

Hallmarks:

Most menstruators have some primary dysmenorrhea. About 1 in 5 have it severely enough to disrupt activity. Below that threshold, it's biology working as designed.

Sorting yourself in 30 seconds

Two-question triage:

  1. Are your cycles regular?
    • No, often irregular or skipped → PMOS first
    • Yes → continue
  2. Is bleeding the dominant problem, or is pain?
    • Both equally bad and bleeding is very heavy → adenomyosis
    • Pain is dominant and shows up in places beyond the uterus (deep sex, bowel, bladder) → endometriosis
    • Pain is confined to your period and OTC meds help → primary dysmenorrhea

If two answers point to two different conditions, that's normal - all four overlap. About 1 in 5 women with endometriosis also have adenomyosis. PMOS and endometriosis coexist at higher-than-chance rates. The right next step is a workup, not self-diagnosis.

How tracking helps with all four

The patterns that distinguish these conditions show up in cycle and symptom logs over time, not in any single visit:

Before any workup, get two to three cycles of data. Then bring it to a doctor with a specific ask.

What to do next

  1. Run the relevant symptom checker.
  2. Map your cycle. Use the Menstrual Cycle Calculator to know which cycle day each symptom lands on.
  3. Track daily for 2-3 cycles with the Femora app, then export the log.
  4. Request a transvaginal ultrasound as a baseline; for adenomyosis or deep endometriosis, ask about MRI.
  5. Cite specific guidelines. ACOG 2026 for endometriosis. The May 2026 PMOS consensus for renamed PCOS.

How Femora helps

Femora's tracking is built to support exactly this kind of differential. Cycle-phase-aware logging, symptom-by-symptom history, exportable reports, and stage-aware modes for cycle tracking through pregnancy, postpartum, and perimenopause. None of these conditions go away on their own; all of them improve faster with good data. See all tools for the full set.

The bigger picture

The biggest medical advance in women's health in 2026 isn't a new drug or scan - it's medical language catching up to lived experience. Renaming PCOS to PMOS, redefining endometriosis to allow clinical diagnosis, separating adenomyosis as its own entity - all three are about reducing the years between "something is wrong" and "here is what it is and what to do." The tools and trackers exist. Knowing which condition you're investigating is the first step.

Track your cycle, pain, and symptoms day-by-day with Femora. Free on iOS and Android.

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