Obesity <-> Polycystic Ovary Syndrome

name: com_Obesity__Polycystic_Ovary_Syndrome
creation_date: "2026-08-27T00:00:00Z"
curation_status: CANDIDATE
notes: >-
  Split out of `kb/disorders/Polycystic_Ovary_Syndrome.yaml`'s `environmental:`
  block (dismech#8296, dismech#8551). That entry listed `Obesity` as an exposure
  with the note "Exacerbates insulin resistance and hyperandrogenism", but
  obesity is a first-class `Disease` entry in its own right
  (`kb/disorders/Obesity.yaml`) and ECTO has no term that would bind it as an
  exposure.

  Directionality is BIDIRECTIONAL rather than A_BEFORE_B, which is the
  substantive difference from `com_Obesity__Heart_Failure`. The sources describe
  a self-reinforcing cycle: obesity-induced insulin resistance worsens the
  features of PCOS, and PCOS-associated androgen excess promotes visceral
  adiposity in turn. Asserting a direction here would pick one arm of a loop the
  literature explicitly declines to break.

  Two qualifiers worth keeping visible. Obesity is neither necessary nor
  sufficient for PCOS, and the association is not universal across national,
  cultural and ethnic groups, so this is a modifier relationship rather than a
  causal prerequisite. And visceral adiposity specifically, which is common in
  women with PCOS whether or not they are obese by body-mass index, is what the
  amplifying effect tracks -- so a body-mass-index-defined obesity entry
  understates the relationship in lean patients.

disease_a:
  slug: Obesity
  preferred_term: obesity disorder
  term:
    id: MONDO:0011122
    label: obesity disorder

disease_b:
  slug: Polycystic_Ovary_Syndrome
  preferred_term: polycystic ovary syndrome
  term:
    id: MONDO:0008487
    label: polycystic ovary syndrome

directionality: BIDIRECTIONAL
effect_direction: RISK

hypotheses:
- description: >-
    Obesity and polycystic ovary syndrome reinforce one another through insulin
    resistance. Adiposity-driven insulin resistance amplifies ovarian and
    adrenal androgen production and worsens ovulatory dysfunction, while
    androgen excess promotes visceral fat deposition and further impairs insulin
    sensitivity, closing the loop.
  evidence:
  - reference: PMID:20591140
    reference_title: "Polycystic ovary syndrome: a complex condition with psychological, reproductive and metabolic manifestations that impacts on health across the lifespan."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Importantly, PCOS has unique interactions with the ever increasing obesity prevalence worldwide as obesity-induced insulin resistance significantly exacerbates all the features of PCOS."
    explanation: >-
      States the mechanism and direction the original environmental note
      asserted: obesity acts on PCOS through insulin resistance, and does so
      across the syndrome's features rather than one of them.
  - reference: PMID:40580384
    reference_title: The Efficacy of Various Weight Loss Strategies in Alleviating Polycystic Ovary Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The bidirectional relationship between PCOS and obesity contributes to a self-reinforcing and deleterious cycle."
    explanation: >-
      The basis for typing this association BIDIRECTIONAL rather than picking a
      direction. Cited for the directionality claim specifically, not for the
      weight-loss interventions the review evaluates.
- description: >-
    The amplifying effect tracks visceral adiposity rather than body weight as
    such, and obesity is a modifier of the phenotype rather than a prerequisite
    for it.
  evidence:
  - reference: PMID:30445140
    reference_title: "Characteristics of obesity in polycystic ovary syndrome: Etiology, treatment, and genetics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Obesity, particularly visceral adiposity which is common in obese and non-obese women with PCOS, amplifies and worsens all metabolic and reproductive outcomes in PCOS."
    explanation: >-
      Locates the effect in visceral adiposity, which is present in lean women
      with PCOS as well, so a body-mass-index-defined entry understates the
      relationship.
  - reference: PMID:30445140
    reference_title: "Characteristics of obesity in polycystic ovary syndrome: Etiology, treatment, and genetics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Obesity is neither necessary nor sufficient for the PCOS phenotype, and the association of PCOS with obesity is not universal, with national, cultural, and ethnic differences."
    explanation: >-
      Bounds the claim. PARTIAL because it qualifies the association rather than
      supporting it: obesity modifies the phenotype without being required for
      it, and the strength of the association varies by population.

association_signals:
- source: LITERATURE
  method: LITERATURE_ASSOCIATION
  population: >-
    Women with polycystic ovary syndrome, as summarised across reported series;
    the range is wide because ascertainment and diagnostic criteria differ
    between them, which is the same population-dependence the second hypothesis
    above records.
  directionality: BIDIRECTIONAL
  effect_direction: RISK
  statistics:
    metrics:
    - metric_type: PREVALENCE
      metric_value: 40.0
      notes: >-
        Lower bound of the reported overweight-or-obese proportion among women
        with PCOS; the upper bound is 85%. Recorded as a co-occurrence
        prevalence, not a directed risk estimate: this association is typed
        BIDIRECTIONAL, so neither arm has a forward cohort measurement here, and
        the figure says how often the two are seen together rather than how much
        either raises the other.
    evidence:
    - reference: PMID:40352401
      reference_title: "PCOS and Obesity: Contraception Challenges."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A significant proportion of women with PCOS, ranging from 40 to 85%, are either overweight or obese."
      explanation: >-
        Quantifies how often the two co-occur. The width of the range is itself
        informative and consistent with the qualifier above that the association
        is not universal across populations.