Diagnostic Criteria for PCOS (Polycystic Ovary Syndrome)
PCOS is diagnosed when at least 2 of 3 Rotterdam criteria are met: (1) androgen excess (clinical or biochemical), (2) ovulatory dysfunction, or (3) polycystic ovarian morphology on ultrasound—after excluding other disorders that mimic PCOS. 1
The Three Core Diagnostic Features
1. Androgen Excess
- Clinical hyperandrogenism: Hirsutism (terminal hair growth), acne, or alopecia 1
- Biochemical hyperandrogenism: Elevated total or free testosterone, or elevated free androgen index 2
- Document findings systematically using standardized tools when possible
2. Ovulatory Dysfunction
- Oligomenorrhea or amenorrhea
- Screen ovulatory status primarily through menstrual history 1
- Midluteal serum progesterone can serve as an additional screening test in women with seemingly regular cycles 1
3. Polycystic Ovarian Morphology (PCOM)
- Ultrasound criteria: At least one ovary with ≥12 follicles measuring 2-9 mm OR ovarian volume >10 mL (in absence of dominant follicle >10 mm) 1
- Important caveat: Universal screening with ultrasound is NOT required if two criteria are already met clinically 1
Critical Exclusions Required
All women must be screened to exclude mimicking disorders 1:
Mandatory screening tests:
- TSH (thyroid disease)
- Prolactin (hyperprolactinemia—can present with amenorrhea or hirsutism)
- 17-hydroxyprogesterone (17-OHP) (nonclassic congenital adrenal hyperplasia, found in 1.5-6.8% of patients with androgen excess) 1
Additional evaluation for select presentations:
In women with amenorrhea, virilization, or atypical features (proximal muscle weakness suggesting Cushing's, frontal bossing suggesting acromegaly), consider broader differential diagnosis 1
Special Population Considerations
Adolescents (Critical Differences)
Diagnosis requires BOTH hyperandrogenism (clinical and/or biochemical) AND persistent oligomenorrhea after excluding other pathologies 1
Do NOT use:
- Anovulatory symptoms alone (85% of cycles are anovulatory in first year post-menarche, 59% in third year) 1
- Polycystic ovarian morphology alone (overlaps with normal pubertal development) 1
- Acne in isolation (too common and transitory in adolescence) 1
Wait at least 2 years post-menarche before evaluating persistent oligomenorrhea as a PCOS feature 1
Postmenopausal Women
No established diagnostic criteria exist 1. Diagnosis can be presumed based on well-documented long-term history of oligomenorrhea and hyperandrogenism during reproductive years. PCOM on ultrasound provides supportive evidence but is less likely present 1
Practical Clinical Algorithm
Step 1: Document presence of 2 of 3 Rotterdam criteria clinically
- Menstrual history for ovulatory dysfunction
- Physical exam for hirsutism, acne, alopecia, acanthosis nigricans
- If 2 criteria already met clinically, proceed to Step 2
Step 2: Obtain mandatory exclusion labs
- TSH, prolactin, 17-OHP
Step 3: Consider additional testing only if needed
- Androgen assays (total/free testosterone or free androgen index) if biochemical confirmation needed
- Pelvic ultrasound only if needed to establish third criterion
- Anti-Müllerian hormone is NOT recommended for diagnosis 2
Common Pitfalls to Avoid
Do not require all three criteria—only 2 of 3 are needed 1
Do not perform universal androgen or ultrasound screening if clinical criteria already establish diagnosis 1
Do not diagnose adolescents using adult criteria—they require both hyperandrogenism AND persistent oligomenorrhea 1
Do not use ultrasound within 8 years of menarche for PCOS diagnosis 3
Do not forget mandatory exclusion testing—PCOS remains a diagnosis of exclusion 1
Document which specific features led to diagnosis to enable phenotype-specific risk stratification (hyperandrogenism associates more with metabolic abnormalities; irregular menses and PCOM associate more with infertility) 1
The Rotterdam criteria endorsed by the 2013 Endocrine Society guidelines 1 and supported by NIH consensus 1 represent the current gold standard, allowing diagnosis through clinical history alone when appropriate while maintaining rigor through mandatory exclusion of mimicking disorders.