Can Polycystic Ovary Syndrome (PCOS) be diagnosed even if menstrual periods are regular?

PCOS Diagnosis with Regular Menstrual Cycles

Yes, PCOS can be diagnosed even in women with regular menstrual periods, as the Rotterdam criteria require only two out of three diagnostic features, which include hyperandrogenism and polycystic ovarian morphology in addition to oligo/anovulation.

Diagnostic Criteria for PCOS

• According to the Rotterdam criteria, PCOS diagnosis requires at least two of the following three features:

  • Oligo- or anovulation
  • Clinical and/or biochemical signs of hyperandrogenism
  • Polycystic ovaries identified on ultrasonography 1, 2

• Women with regular menstrual cycles can still meet diagnostic criteria if they have both:

  • Clinical or biochemical hyperandrogenism (e.g., hirsutism, acne, elevated testosterone)
  • Polycystic ovarian morphology on ultrasound 1, 3

PCOS Phenotypes

• Four distinct PCOS phenotypes have been recognized:

  • Phenotype A: Hyperandrogenism, chronic anovulation, and polycystic ovaries
  • Phenotype B: Hyperandrogenism and chronic anovulation
  • Phenotype C: Hyperandrogenism and polycystic ovaries with normal menstrual cycles
  • Phenotype D: Chronic anovulation and polycystic ovaries without hyperandrogenism 4, 3

• Phenotype C specifically includes women with regular menstrual cycles who still have PCOS 3

Diagnostic Evaluation

Clinical Assessment

• Even with regular cycles, look for:
  • Signs of hyperandrogenism: hirsutism, acne (especially severe or treatment-resistant), male-pattern hair loss 1
  • Obesity or increased waist-hip ratio (>0.9) suggesting truncal obesity 4
  • Infertility despite regular cycles 4

Laboratory Testing

• Hormonal evaluation should include:
  • Free testosterone levels (more sensitive than total testosterone) 1
  • LH/FSH ratio (ratio >2 suggests PCOS) 4
  • Fasting glucose/insulin ratio to assess insulin resistance 4
  • Rule out other conditions: thyroid dysfunction, hyperprolactinemia, congenital adrenal hyperplasia 2

Imaging

• Transvaginal ultrasound is preferred for evaluating ovarian morphology 4
• Diagnostic criteria for polycystic ovaries:
  • ≥20 follicles (2-9mm) in at least one ovary using high-resolution transvaginal ultrasound, or
  • Ovarian volume ≥10ml in at least one ovary 4, 5
• The presence of a single polycystic ovary is sufficient for diagnosis 5

Important Considerations

• Regular cycles do not guarantee ovulation; some women with PCOS may have regular but anovulatory cycles 1
• Progesterone levels measured during the mid-luteal phase can confirm whether ovulation is occurring despite regular cycles 4
• Anti-Müllerian hormone (AMH) levels are often elevated in PCOS but should not be used as the sole diagnostic test 4

Common Pitfalls to Avoid

• Assuming regular cycles rule out PCOS 3
• Relying solely on ultrasound findings without clinical or biochemical evidence of hyperandrogenism 4
• Failing to screen for metabolic abnormalities in women with PCOS and regular cycles, who still have increased risk for insulin resistance and cardiovascular disease 6
• Not considering PCOS in adolescents with hyperandrogenism but regular cycles (noting that diagnostic criteria differ slightly for adolescents) 3

Health Implications

• Even with regular cycles, women with PCOS should be monitored for:
  • Metabolic abnormalities including insulin resistance and dyslipidemia 6
  • Increased cardiovascular risk 6
  • Potential endometrial hyperplasia (even with apparently regular cycles) 6, 1
  • Fertility issues 1, 2

Remember that PCOS is a heterogeneous condition, and the clinical presentation can vary significantly between individuals. Regular menstrual cycles do not exclude the diagnosis if other diagnostic criteria are met.