Polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS), recently referred also as hyperandrogenic anovulation, is a chronic anovulation syndrome associated with androgen excess. 

The diagnosis is made on the combined clinical, biochemical and sonographic grounds. The revised 2003 ASRM/ESHRE Rotterdam consensus criteria 4 require two of the following three criteria for the diagnosis:

  1. oligo- or anovulation
  2. hyperandrogenism (clinical or biochemical) and
  3. follicle count on imaging

As well as the exclusion of other aetiologies, such as congenital adrenal hyperplasia, Cushing syndrome and/or an androgen-secreting tumour.

Subsequently, the Androgen Excess and PCOS society (AE-PCOS) 9 specified a similar set of criteria for diagnosing PCOS but added that PCOS should be seen primarily as a disorder of androgen excess or hyperandrogenism. The criteria set forward was:

  1. presence of hyperandrogenism (clinical and/or biochemical)
  2. ovarian dysfunction (oligo-anovulation and/or polycystic ovaries)
  3. exclusion of related disorders

Hyperandrogenic anovulation has been proposed as more accurate and potentially less confusing term, as the ovarian feature is of multiple follicles and not cysts13. At this stage, however, PCOS remains the term that is widely known and used.

The estimated prevalence is ~6% (range 4-8%) of women of reproductive age but this varies (up to 20%) depending on the diagnostic criteria used 11

The classic triad of PCOS is:

  1. oligomenorrhea
  2. hirsutism
  3. obesity

In addition to this, patients may have infertility, acne, male pattern balding or biochemically show increased androgen levels.

Luteinizing hormone (LH) is usually increased and follicle stimulating hormone (FSH) can be normal or decreased 10.

Normally premenopausal LH:FSH is 1:1. In PCOS it may be >2:1 or >3:1.

Anti-Müllerian hormone (AMH) levels are generally increased.

  • subfertility and recurrent pregnancy loss.
  • long-term increased risk of
  • women with polycystic ovarian morphology are at increased risk of OHSS when undergoing IVF, regardless of whether they have PCOS15

Current recommended sonographic criteria for multifollicular ovarian morphology: 

  • 25 or more follicles per ovary (superseding the earlier Rotterdam criteria of 12 or more follicles) 14
  • increased ovarian size (>10 cc): less sensitive than the follicle number criteria, but has a role when image resolution does not allow accurate follicle count, e.g. transabdominal scanning, older equipment

Other morphological features include:

  • hyperechoic central stroma
  • peripheral location of follicles: which can give a string of pearl appearance
  • follicles of similar size measuring 2-9 mm

The presence of a single multifollicular ovary is sufficient to provide the sonographic criterion for PCOS2.

Ovaries may be normal in PCOS, and conversely, polycystic ovaries may be seen in women without the syndrome. Diagnosis requires correlation with features of hyperandrogenism and oligo-anovulation.

MRI is not warranted routinely in the investigation of PCOS, nonetheless pelvic MRI may show most or all of the above sonographic features. Signal characteristics include:

  • T1: small uniform follicles are low in signal while the central stroma is of intermediate signal (vs normal myometrium)
  • T2: follicles have high T2 signal while the central stroma is of comparatively low T2 signal 8
  • with a lack of consensus sometimes it is easier to report the number of follicles in each ovary rather than attempt to label the ovaries as "polycystic" or "multifollicular"

The syndrome was first described by I.F. Stein and M.L. Leventhal in 1935 7.

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Article information

rID: 4620
System: Gynaecology
Section: Syndromes
Synonyms or Alternate Spellings:
  • PCOS
  • Polycystic ovary syndrome
  • Polycystic ovarian syndrome
  • Sclerocystic ovarian disease
  • Stein-Leventhal syndrome
  • Anovulation with hyperandrogenism
  • Rotterdam consensus criteria
  • Rotterdam criteria
  • Hyperandrogenic anovulation
  • Rotterdam consensus criteria

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