Polycystic Ovarian Syndrome (PCOS)



  • Polycystic ovarian syndrome (PCOS) is a common endocrine disorder with heterogeneous manifestations that affects 6–10% of the U.S. population. It is characterized by hyperandrogenism, insulin resistance, and anovulation, typically presenting as amenorrhea or oligomenorrhea.
  • Diagnostic clinical characteristics include menstrual dysfunction, infertility, hirsutism, acne, obesity, and metabolic syndrome. The ovaries are often polycystic on imaging.
  • The etiology of PCOS is unknown, but presentation and course can be modified by lifestyle factors.
  • System(s) affected: reproductive, endocrine/metabolic, skin/exocrine
  • Synonym(s): Stein-Leventhal syndrome; polycystic ovary disease
  • Obesity may amplify PCOS, but it is not diagnostic.
  • 20% of women with PCOS are not obese.
  • Predisposes to and is associated with obesity, hypertension, type 2 diabetes mellitus, metabolic syndrome, hyperlipidemia, infertility, insulin-resistance syndrome, endometrial hyperplasia, and uterine cancer


Incidence and prevalence are still highly debated due to a wide spectrum of diagnostic features; the National Institutes of Health (NIH) criteria require chronic anovulation and hyperandrogenism.

The prevalence based on NIH criteria is 7% of reproductive age women.

Etiology and Pathophysiology

  • Recent evidence points to a primary role for insulin resistance with hyperinsulinemia.
  • Increased GnRH pulsations in the hypothalamus lead to increased production of LH with limited production of FSH.
  • Hyperandrogenism: Ovaries are the main source of excess androgens (75% of circulating testosterone originates in the ovary). Polycystic ovaries have thickened thecal layers and overexpressed LH receptors, which cause excess androgen secretion.
  • Ovarian follicles: Abnormal androgen signaling may account for abnormal folliculogenesis causing polycystic ovaries.
  • Obesity results in compensatory hyperinsulinemia: Women with PCOS have insulin resistance similar to that in type 2 diabetes. Elevated levels of insulin decrease sex hormone–binding globulin (SHBG), increasing bioavailability of testosterone. Insulin may also act directly on adrenal glands, ovaries, and hypothalamus to enhance androgen production.
  • Insulin resistance causes elevated insulin levels and the frequently associated metabolic syndrome or frank diabetes mellitus.

Likely a combination of polygenic and environmental factors; implicated genes include DENND1A and THADA.

Risk Factors

See “Commonly Associated Conditions”; cause and effect are difficult to extricate in this disorder.

General Prevention

None known; focus on early diagnosis and treatment to prevent long-term complications.

Commonly Associated Conditions

Infertility, obesity, obstructive sleep apnea, hypertension, diabetes mellitus, endometrial hyperplasia/carcinoma, fatty liver disease, mood disturbances and depression, hirsutism

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