PMOS terms, plainly.
Plain-language definitions of the PMOS terms that come up most often in research, clinical conversations, and Cyster’s knowledge articles.
Acanthosis nigricans
Velvety, darkened patches of skin, often at the neck, armpits, or groin. A visible sign of high circulating insulin.
Read →Androgenic alopecia
Hair thinning in an androgen-driven pattern, usually at the crown and along the part. Common in PMOS, and often reversible when the underlying signal is addressed.
Read →Androgens
A group of hormones, including testosterone, present in everyone. In PMOS they often run higher than typical, which drives several of the visible signs.
Read →Anovulation
When a menstrual cycle does not release an egg. One of the three Rotterdam criteria for PMOS, and the most common reason fertility takes longer in this condition.
Read →Anti-Müllerian hormone (AMH)
A hormone released by small ovarian follicles. Often high in PMOS, because there are more of those follicles than usual.
Read →Antral follicle
A small, fluid-filled sac in the ovary that holds an immature egg. The structures that get miscounted as "cysts" in the old PCOS name.
Read →Cardiometabolic risk
The combined risk to the heart and metabolism, elevated in PMOS even in younger women. A reason to address metabolic health early, not later.
Read →Chronic low-grade inflammation
A low, persistent activation of the immune system, well-documented in PMOS and linked to both insulin resistance and androgen production.
Read →Compensatory hyperinsulinaemia
Chronically high insulin levels, produced when the pancreas works overtime to keep glucose normal. The hidden middle of insulin resistance.
Read →DHEAS
An androgen made by the adrenal glands. Elevated in a subset of PMOS, marking a second, parallel androgen source alongside the ovary.
Read →Fasting insulin
A blood test that measures insulin, not glucose, after fasting. More sensitive to early insulin resistance than fasting glucose.
Read →Free testosterone
The active, unbound fraction of testosterone. Often elevated in PMOS even when total testosterone reads normal.
Read →GLP-1 receptor agonist
A class of medication (including semaglutide and tirzepatide) that affects insulin, appetite, and weight. Increasingly used in PMOS, on a clinician’s lead.
Read →Hirsutism
Coarse, dark hair growth in a male-pattern distribution, such as the chin, upper lip, and lower abdomen. One of the most evidenced androgenic signs.
Read →HOMA-IR
A calculation that estimates insulin resistance from a single blood draw. Often elevated in PMOS even when fasting glucose alone looks normal.
Read →HPO axis
The hypothalamic-pituitary-ovarian axis, the signalling chain between brain and ovary that runs the menstrual cycle. Disrupted in PMOS.
Read →Hyperandrogenism
Higher-than-typical androgen activity, measured in the blood or seen in signs like acne and hirsutism. One of the three Rotterdam criteria.
Read →Inositol
A supplement with the largest evidence base for PMOS, usually myo-inositol with a small share of d-chiro-inositol. Studied for insulin sensitivity and ovulation.
Read →Insulin resistance
When cells respond less to insulin, the pancreas releases more to do the same job. In PMOS, this loops with ovarian androgen production.
Read →LH and FSH
Two pituitary hormones that drive ovulation. In PMOS their balance is often skewed toward LH, part of why ovulation stalls.
Read →Metformin
A long-used prescription medication that improves insulin sensitivity. Common in PMOS care, especially around conception.
Read →Oligomenorrhoea
Infrequent periods, defined as cycles longer than 35 days or fewer than about nine a year. A common cycle pattern in PMOS.
Read →Oral glucose tolerance test (OGTT)
A timed test that tracks glucose, and ideally insulin, after a standard glucose drink. The most detailed common test for insulin resistance.
Read →PMOS
Polyendocrine metabolic ovarian syndrome, the 2026 name for the condition formerly called PCOS. A multisystem endocrine and metabolic condition.
Read →Polycystic ovary morphology (PCOM)
The ultrasound appearance of many small follicles in the ovary. One of the three Rotterdam criteria, and the source of the old, inaccurate "polycystic" name.
Read →Rotterdam criteria
The diagnostic framework for PMOS: two of three among hyperandrogenism, ovulation problems, and polycystic ovary morphology, with other causes excluded.
Read →SHBG
Sex hormone-binding globulin. The protein that holds testosterone out of circulation. Often low in PMOS, which raises free testosterone even when total looks normal.
Read →Theca cells
Cells in the ovary that produce androgens. In PMOS, insulin drives them to make more, which is the start of the insulin-androgen loop.
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