Reproductive · PANCE / PANRE

Polycystic Ovary Syndrome (PCOS)

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Hyperandrogenism + ovulatory dysfunction + polycystic ovarian morphology; insulin resistance is the common thread.

Also known as: PCOS, Stein-Leventhal syndrome, polycystic ovaries, functional ovarian hyperandrogenism

Overview

Heterogeneous endocrine disorder of reproductive-age women defined (Rotterdam 2003) by 2 of 3 criteria: oligo- or anovulation, clinical or biochemical hyperandrogenism, and polycystic ovarian morphology on ultrasound — after exclusion of other causes.

Epidemiology

Affects 8-13% of reproductive-age women worldwide; most common endocrinopathy in this group and a leading cause of anovulatory infertility.

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Question 1ReproductiveMedium
A 28-year-old woman with obesity has oligomenorrhea, hirsutism, and acne. Pelvic ultrasound shows bilateral ovaries each with >=20 follicles. Laboratory studies show an elevated LH (luteinizing hormone):FSH (follicle-stimulating hormone) ratio and a mildly elevated free testosterone. Which of the following is the most appropriate first-line management?
  • ALifestyle modification
  • BEstrogen replacement
  • CGlucocorticoid replacement
  • DLaparoscopic ovarian drilling
Reveal answer & full explanation
Correct answer: A — Lifestyle modification
  • ALifestyle modification✓
  • BEstrogen replacement
  • CGlucocorticoid replacement
  • DLaparoscopic ovarian drilling

Why lifestyle modification is correct

  • Oligomenorrhea, clinical and biochemical hyperandrogenism (hirsutism, acne, elevated free testosterone), and polycystic ovarian morphology satisfy the Rotterdam criteria (2 of 3) for polycystic ovary syndrome.
  • In a patient with obesity, lifestyle modification with 5-10% weight loss is first-line: it lowers androgens, improves insulin sensitivity, and restores ovulation in many patients.
  • Combined oral contraceptives, metformin, and letrozole are added for menstrual regulation, insulin resistance, and ovulation induction respectively, but behavioral change comes first.

Why the others are wrong

  • Estrogen replacement — these patients are estrogen-replete; unopposed estrogen would worsen endometrial risk and does not treat hyperandrogenism. Sets the confused-with-hypoestrogenism trap.
  • Glucocorticoid replacement — reserved for adrenal causes of hyperandrogenism such as non-classic congenital adrenal hyperplasia; the LH:FSH ratio and ovarian morphology point to an ovarian source. Sets the confused-with-CAH trap.
  • Laparoscopic ovarian drilling — a later-line option for ovulation induction in patients resistant to letrozole or clomiphene, and it addresses neither the metabolic driver nor the hirsutism. Sets the right-treatment-wrong-step trap.
Question 2ReproductiveMedium
A 25-year-old woman reports menstrual cycles every 45 to 60 days, increasing facial and chin hair, and difficulty losing weight; her BMI is 32. Examination shows coarse terminal hair on the upper lip and chin. Laboratory studies reveal elevated free testosterone, a normal 17-hydroxyprogesterone, normal TSH and prolactin, and a luteinizing hormone to follicle-stimulating hormone ratio of 3:1. Transvaginal ultrasound shows multiple small peripheral follicles in each ovary. After excluding other causes, which of the following combinations of findings establishes the diagnosis of polycystic ovary syndrome by the Rotterdam criteria?
  • AElevated free testosterone with an elevated fasting insulin level
  • BPolycystic ovarian morphology with fasting hyperinsulinemia
  • COligo-ovulation with an elevated LH to FSH ratio above 2
  • DOligo-ovulation with clinical or biochemical hyperandrogenism
Reveal answer & full explanation
Correct answer: D — Oligo-ovulation with clinical or biochemical hyperandrogenism
  • AElevated free testosterone with an elevated fasting insulin level
  • BPolycystic ovarian morphology with fasting hyperinsulinemia
  • COligo-ovulation with an elevated LH to FSH ratio above 2
  • DOligo-ovulation with clinical or biochemical hyperandrogenism✓

Why Oligo-ovulation with clinical or biochemical hyperandrogenism is correct

  • Polycystic ovary syndrome (PCOS) is diagnosed by the Rotterdam criteria, which require at least two of three features after excluding mimics: (1) oligo- or anovulation, (2) clinical or biochemical hyperandrogenism, and (3) polycystic ovarian morphology on ultrasound.
  • This patient has cycles longer than 35 days (oligo-ovulation), hirsutism with elevated free testosterone (hyperandrogenism), and polycystic morphology — meeting all three criteria.
  • Oligo-ovulation combined with clinical or biochemical hyperandrogenism satisfies the required two-of-three even if the ovaries appeared normal on ultrasound, establishing the diagnosis.

Why the others are wrong

  • Polycystic ovarian morphology with fasting hyperinsulinemia — polycystic morphology supplies one Rotterdam criterion, but hyperinsulinemia is not a criterion at all, so this pairing still yields only one of the two required features.
  • Oligo-ovulation with an elevated LH to FSH ratio above 2 — an elevated LH:FSH ratio is a frequently observed laboratory finding in PCOS but is not one of the three Rotterdam criteria, so oligo-ovulation stands alone here and a single criterion is never sufficient.
  • Elevated free testosterone with an elevated fasting insulin level — insulin resistance is common in PCOS but is not a Rotterdam criterion; this pairing supplies only one true criterion (hyperandrogenism) and therefore cannot confirm the diagnosis.

Additional high-yield points

  • Essential exclusions before applying the Rotterdam criteria include congenital adrenal hyperplasia (assessed with 17-hydroxyprogesterone), thyroid disease (TSH), and hyperprolactinemia — all ruled out in this case.
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Risk factors

  • Family history of PCOS or type 2 diabetes
  • Obesity, particularly central adiposity
  • Premature adrenarche, low birth weight
  • Insulin resistance, metabolic syndrome

Pathophysiology

Insulin resistance with compensatory hyperinsulinemia augments LH-driven ovarian theca cell androgen production and suppresses hepatic SHBG, increasing free testosterone. Elevated LH:FSH ratio impairs follicular maturation, producing arrested antral follicles (the 'polycystic' appearance) and anovulation. Unopposed estrogen exposure raises endometrial cancer risk.

Clinical presentation

Symptoms

  • Oligomenorrhea or amenorrhea, typically since menarche
  • Hirsutism (upper lip, chin, chest, abdomen, back)
  • Acne, androgenic alopecia
  • Infertility, recurrent pregnancy loss
  • Weight gain, difficulty losing weight

Signs / physical exam

  • BMI often elevated; central adiposity
  • Acanthosis nigricans (insulin resistance marker)
  • Modified Ferriman-Gallwey score ≥4-8 (population-dependent)
  • Acne, male-pattern hair thinning

Classic findings

Young woman with irregular menses, hirsutism, acne, and obesity; ultrasound with ≥20 follicles per ovary or ovarian volume >10 mL.

Differential diagnosis

  • Thyroid disease — Menstrual irregularity from hypo- or hyperthyroidism; check TSH
  • Hyperprolactinemia — Galactorrhea, amenorrhea; prolactin elevated; consider pituitary adenoma
  • Non-classic congenital adrenal hyperplasia (21-hydroxylase deficiency) — Hirsutism with elevated 17-hydroxyprogesterone (early morning, follicular phase >200 ng/dL warrants ACTH stim)
  • Cushing syndrome — Central obesity, striae, easy bruising, proximal weakness; abnormal dexamethasone suppression or 24-h urine cortisol
  • Androgen-secreting tumor (ovarian or adrenal) — Rapid virilization, total testosterone >150-200 ng/dL or DHEAS markedly elevated; imaging
  • Primary ovarian insufficiency — Amenorrhea with elevated FSH and low estradiol
  • Hypothalamic amenorrhea — Low BMI, excessive exercise, stress; low FSH/LH and low estradiol
  • Idiopathic hirsutism — Regular menses, normal androgens

Diagnostic workup

Diagnostic criteria

Rotterdam criteria (2 of 3): (1) oligo- or anovulation, (2) clinical or biochemical hyperandrogenism, (3) polycystic ovarian morphology on ultrasound — AFTER excluding thyroid disease, hyperprolactinemia, NCCAH, Cushing, and androgen-secreting tumors.

Labs

  • Total and free testosterone, SHBG, DHEAS
  • TSH, prolactin, 17-hydroxyprogesterone (early-morning follicular)
  • Fasting glucose and 2-h OGTT, A1c, lipid panel
  • If amenorrhea: FSH, LH, estradiol, urine hCG
  • Endometrial biopsy if prolonged amenorrhea or abnormal bleeding (rule out hyperplasia)

Imaging

  • Transvaginal pelvic ultrasound: ≥20 follicles per ovary (2-9 mm) and/or ovarian volume >10 mL (per 2018 international guideline)
  • Ultrasound morphology is NOT required if irregular menses + hyperandrogenism present; also not used in adolescents within 8 years of menarche

Diagnostic algorithm

DomainFindingWorkup
Ovulatory dysfunctionOligomenorrhea (<8 cycles/yr) or amenorrheaCycle history; progesterone if uncertain
Hyperandrogenism (clinical)Hirsutism, acne, androgenic alopeciaModified Ferriman-Gallwey score
Hyperandrogenism (biochemical)Elevated total/free testosterone, DHEASMorning total + free testosterone, SHBG
Polycystic morphology≥20 follicles/ovary or volume >10 mLTransvaginal ultrasound (not in adolescents)
Exclude mimicsNormal TSH, prolactin, 17-OHP, cortisolTSH, prolactin, 17-OHP, dexamethasone suppression if indicated
Rotterdam criteria for PCOS — 2 of 3 features required after exclusion of mimics.

Treatment

First-line

  • Lifestyle modification: 5-10% weight loss restores ovulation in many; Mediterranean-style diet, 150 min/wk moderate exercise
  • Combined oral contraceptive (COCP) — ethinyl estradiol/levonorgestrel, drospirenone, or norethindrone — for menstrual regulation, hirsutism, acne; protects endometrium
  • Metformin — improves insulin sensitivity, modest weight loss, restores ovulation in some; first-line for impaired glucose tolerance

Infertility / ovulation induction

  • Letrozole — first-line (superior live birth vs clomiphene in PCOS per PPCOS II trial)
  • Clomiphene citrate — second-line
  • Gonadotropins or IVF if oral agents fail

Hirsutism

  • COCP × 6 months before judging response
  • Add spironolactone 50-200 mg/day (anti-androgen) — must be paired with reliable contraception (teratogen)
  • Eflornithine cream for facial hair; mechanical/laser hair removal as adjunct

Endometrial protection if COCP contraindicated

  • Cyclic progestin (medroxyprogesterone 5-10 mg × 10-14 days every 1-3 months)
  • Levonorgestrel IUD

Second-line / adjunct

  • GLP-1 receptor agonists (semaglutide, liraglutide) for weight loss in obese patients
  • Bariatric surgery for BMI ≥35 with comorbidities
  • Inositol supplementation — modest evidence, low risk

Complications

  • Type 2 diabetes (4x risk), metabolic syndrome, NAFLD
  • Endometrial hyperplasia and endometrial carcinoma (from chronic unopposed estrogen)
  • Infertility, increased miscarriage rate, gestational diabetes, preeclampsia
  • Obstructive sleep apnea, depression and anxiety
  • Possible increased risk of cardiovascular disease

PANCE pearls

  • Letrozole has replaced clomiphene as first-line for ovulation induction in PCOS-associated infertility.
  • Spironolactone is teratogenic (feminization of male fetus) — always combine with effective contraception.
  • Adolescent diagnosis requires BOTH hyperandrogenism AND persistent oligomenorrhea (≥2 years post-menarche); ultrasound morphology should not be used.
  • Screen all PCOS patients for diabetes with a 2-h OGTT (more sensitive than A1c or fasting glucose alone) every 1-3 years.
  • Prolonged amenorrhea (>3 months) warrants either withdrawal bleed induction with progestin or endometrial sampling.

References

  • International PCOS Guideline 2023 — 2023 International Evidence-Based Guideline for the Assessment and Management of Polycystic Ovary Syndrome (Teede et al., Fertil Steril 2023)
  • ACOG PB 194 — ACOG Practice Bulletin No. 194: Polycystic Ovary Syndrome (Obstet Gynecol 2018)
  • PPCOS II — Letrozole versus Clomiphene for Infertility in the Polycystic Ovary Syndrome (Legro et al., NEJM 2014)

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EndometriosisUterine Fibroids (Leiomyoma)Abnormal Uterine BleedingPrimary AmenorrheaSecondary AmenorrheaMenopausePelvic Inflammatory Disease (PID)Bacterial VaginosisCandidal VulvovaginitisTrichomoniasisCervical Cancer and HPVEndometrial CancerOvarian CancerBreast Cancer

Differentials & related conditions

Hyperprolactinemia (Drug-Induced, Physiologic, and Pathologic)Cushing Syndrome

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