PCOS and Endometriosis

PCOS — non-modifiable/constitutional

• Polygenic susceptibility: strong familial clustering; first-degree female relatives of affected women have substantially higher rates. Candidate loci cluster in gonadotropin signaling (LHCGR, FSHR) and insulin-signaling pathways.
• Intrauterine androgen exposure: prenatal androgenization is thought to reprogram GnRH pulse generator sensitivity to progesterone feedback, producing the rapid LH pulse frequency described above.
• Ethnicity: hirsutism severity and metabolic risk vary by ancestry (higher metabolic risk in South Asian women), which the International Evidence-based PCOS Guideline (endorsed in the US by ACOG and ASRM) asks clinicians to account for when interpreting hirsutism scores.

PCOS — modifiable

• Obesity, particularly visceral adiposity: amplifies insulin resistance, lowers SHBG, and raises free testosterone; weight gain can convert a subclinical phenotype into overt anovulation, and modest weight loss can restore ovulation.
• Sedentary behavior, obstructive sleep apnea, and valproate exposure: each worsens insulin resistance or directly promotes hyperandrogenism.

Endometriosis — non-modifiable

• Increased lifetime retrograde menstrual flow: early menarche, short cycles, and heavy or prolonged menses raise the volume of refluxed viable endometrium.
• Outflow tract obstruction: imperforate hymen, transverse vaginal septum, or a non-communicating rudimentary uterine horn cause obligate reflux — the classic adolescent stem with cyclic pain and primary amenorrhea.
• Family history: a first-degree relative markedly increases risk, supporting heritable immune/hormonal susceptibility.
• Low BMI and lean body habitus, and nulliparity/infertility (partly reverse causation).

Endometriosis — modifiable or protective

• Prolonged unopposed ovulatory cycling: pregnancy, lactation, and continuous combined hormonal contraception reduce cycles and are protective.
• Distractor to reject: neither condition is caused by "tilted uterus," tampon use, or prior abortion; ACOG attributes retroverted fixed uterus to adhesive disease, not the reverse.

PCOS Pathophysiology

• Insulin resistance and hyperinsulinemia: Present in 50-70% of PCOS patients; hyperinsulinemia stimulates ovarian androgen production via enhanced theca cell steroidogenesis and reduces hepatic sex hormone-binding globulin (SHBG) production, increasing free testosterone levels
• Abnormal hypothalamic-pituitary-ovarian (HPO) axis function: Elevated LH:FSH ratio (typically >3:1) results from increased GnRH pulse frequency; this preferentially stimulates theca cells to produce androgens while inadequately stimulating aromatase in granulosa cells, preventing estrogen production and follicle maturation
• Chronic anovulation: Elevated androgens prevent normal follicle selection and dominance, leading to accumulation of small antral follicles ("polycystic" appearance); lack of ovulation prevents corpus luteum formation and progesterone deficiency, perpetuating unopposed estrogen stimulation
• Chronic inflammation and oxidative stress: Increased inflammatory markers (TNF-α, IL-6), oxidative stress, and altered adipokine signaling contribute to metabolic dysfunction and cardiovascular risk
• Genetic and environmental factors: Likely polygenic inheritance with environmental factors (obesity, fetal androgenization); obesity worsens insulin resistance and hyperandrogenism

Endometriosis Pathophysiology

• Retrograde menstruation with impaired clearance: Menstrual endometrial cells reflux through fallopian tubes; normally cleared by peritoneal immunity, but in endometriosis, reduced NK cell function and impaired macrophage activation allow ectopic implantation and survival
• Molecular alterations in ectopic endometrium: Loss of progesterone receptor (PR-B) expression and altered estrogen receptor signaling create progesterone resistance; ectopic lesions express elevated aromatase (CYP19A1), enabling local estrogen production independent of ovarian synthesis
• Angiogenesis and neuroangiogenesis: VEGF overexpression and abnormal nerve fiber infiltration create a hypervascularized, innervated lesion that is metabolically active and pain-generating
• Impaired apoptosis and enhanced cell survival: Reduced apoptotic signaling allows abnormal endometrial cells to persist; increased anti-apoptotic factors (Bcl-2) and growth factors support ectopic lesion survival
• Stem cell recruitment and bone marrow contribution: Bone marrow-derived progenitor cells may contribute to lesion growth and neovascularization
• Altered peritoneal environment: Elevated prostaglandins (especially PGE2), cytokines (IL-8, IL-6), and growth factors (FGF, HGF) in peritoneal fluid promote inflammation, angiogenesis, and pain

PCOS Presentation

• Menstrual dysfunction: Oligomenorrhea (cycles >35 days) or amenorrhea from chronic anovulation; irregular, heavy, or prolonged menses in ovulatory cycles; abnormal uterine bleeding (AUB) from unopposed estrogen
• Hyperandrogenic signs: Hirsutism (excess terminal hair in androgen-dependent areas: face, chest, abdomen, inner thighs); acne (often resistant to conventional treatment); male-pattern baldness/androgenetic alopecia
• Infertility: Primary or secondary infertility due to anovulation; may present with prolonged time-to-conception or history of miscarriage (associated with insulin resistance and inflammation)
• Metabolic features: Obesity or difficult weight loss (30-50% of PCOS patients); central adiposity; acanthosis nigricans (velvety hyperpigmentation, marker of severe insulin resistance); increased cardiovascular risk factors (dyslipidemia, hypertension, impaired glucose tolerance)
• Ultrasound findings: "String of pearls" appearance with ≥12 small follicles (2-9 mm) in ovaries; may have normal ovarian volume (varies by diagnostic criteria)
• Important variant: Lean PCOS (20-30% of cases) with normal BMI but insulin resistance, metabolic dysfunction, and hyperandrogenism

Endometriosis Presentation

• Dysmenorrhea: Progressive, severe pelvic pain during menstruation that worsens over time (distinguishes from primary dysmenorrhea, which improves with age); may precede visible menstrual bleeding by days
• Dyspareunia: Pain with deep penetration (especially with posterior/uterosacral involvement); may limit sexual function significantly
• Chronic pelvic pain: Acyclic pelvic pain, lower back pain, or pain with bowel movements/urination suggesting bowel or bladder involvement; pain severity does NOT correlate with disease extent
• Infertility: Present in 30-50% of endometriosis patients; mechanisms include mechanical obstruction, altered peritoneal environment, impaired egg quality, and reduced sperm function
• Asymptomatic presentation: 20-30% of women with endometriosis discovered incidentally during imaging or surgery for other indications
• GI/GU symptoms: Diarrhea, constipation, painful bowel movements (colorectal involvement); dysuria, hematuria (urinary involvement)
• Clinical pearl: Absence of pain does NOT rule out endometriosis, and severe pain does NOT indicate advanced disease—histologic stage correlates poorly with symptom severity

PCOS Diagnosis (Rotterdam Criteria - 2 of 3 required)

• Clinical or biochemical hyperandrogenism: Free or total testosterone elevation, clinical hirsutism, acne, or alopecia; biochemical hyperandrogenism is the most consistent finding
• Ovulatory dysfunction: Oligomenorrhea or amenorrhea; ultrasound evidence of polycystic ovaries (≥12 follicles per ovary or ovarian volume ≥10 cm³) even without symptoms
• Exclusion of other hyperandrogenic disorders: Rule out androgen-secreting tumors (very high testosterone >150 ng/dL), Cushing syndrome, congenital adrenal hyperplasia (CAH), and thyroid disease; hyperprolactinemia should be excluded
• Laboratory evaluation: Measure total/free testosterone, LH, FSH, prolactin, TSH, 17-hydroxyprogesterone (to exclude CAH); fasting glucose/insulin or 2-hour glucose tolerance test (GTT) to assess insulin resistance; lipid panel; consider DHEA-S to exclude adrenal pathology if markedly elevated
• Ultrasound findings: Transvaginal ultrasound preferred; polycystic ovaries support diagnosis but NOT required if clinical/biochemical criteria met

Endometriosis Diagnosis

• Gold standard: Laparoscopic visualization and histopathologic confirmation: Direct visualization of lesions (red/pink "powder burn," blue nodules, white/clear peritoneal defects) with tissue biopsy confirming endometrial glands and stroma in ectopic location; however, clinical diagnosis often made on presentation without surgical confirmation
• MRI imaging: Useful for detecting deep infiltrating endometriosis (DIE), especially in rectosigmoid or uterosacral ligaments; shows T2 hyperintense lesions on endometriomas and stromal changes; sensitivity 71-90% for deep disease
• Transvaginal ultrasound (TVUS): Detects ovarian endometriomas (cystic lesions with echogenic debris/"chocolate cyst"), uterine adenomyosis, and deep infiltrating lesions; sensitivity varies by location
• Biomarkers: CA-

PCOS — first-line, driven by the patient's goal

• Lifestyle modification: the International Evidence-based PCOS Guideline (endorsed by ACOG/ASRM) makes weight management and exercise foundational; even modest weight loss restores ovulation by lowering insulin and raising SHBG.
• Combined hormonal contraceptives (e.g., a low-dose estrogen–progestin pill) are first-line when pregnancy is not desired: they suppress LH-driven ovarian androgen output, raise SHBG, and — critically — provide endometrial protection against unopposed estrogen.
• Antiandrogens: spironolactone added for hirsutism refractory to 6 months of an OCP; it blocks the androgen receptor and 5α-reductase. Requires reliable contraception (feminization of a male fetus).
• Insulin sensitizers: metformin for impaired glucose tolerance or type 2 diabetes; it improves cycle regularity but is inferior to OCPs for hirsutism.

PCOS — fertility desired

• Letrozole, an aromatase inhibitor, is first-line ovulation induction per ASRM; it outperformed clomiphene for live birth in PCOS (PPCOS II). Clomiphene is second-line, then gonadotropins or laparoscopic ovarian drilling, then IVF.

Endometriosis — stepwise, per ACOG

• NSAIDs plus continuous combined hormonal contraception are first-line; empiric medical therapy without laparoscopy is acceptable when the presentation is typical.
• Progestins (norethindrone acetate, depot medroxyprogesterone, levonorgestrel IUD) decidualize and atrophy lesions.
• Second-line hypoestrogenic therapy: GnRH agonist (leuprolide) with add-back norethindrone, or oral GnRH antagonist (elagolix); aromatase inhibitors for refractory disease.
• Surgery: laparoscopic excision/ablation of implants and endometrioma cystectomy; hysterectomy with bilateral salpingo-oophorectomy is definitive but not curative for pain.

Contraindicated / avoid

• Hormonal suppression in the infertile patient — it prevents conception; use surgery or IVF instead.
• Unopposed estrogen in PCOS, and estrogen-containing contraceptives with migraine with aura, smoking over age 35, or prior VTE.

PCOS — disease complications

• Endometrial hyperplasia and endometrial carcinoma: chronic anovulation leaves the endometrium under unopposed estrogen without progesterone-mediated differentiation. Signal: prolonged amenorrhea followed by heavy/irregular bleeding, or a thickened endometrial stripe — obtain endometrial biopsy.
• Type 2 diabetes, gestational diabetes, dyslipidemia, hypertension, and NAFLD: insulin resistance is the common mechanism; ADA Standards of Care list PCOS as an indication for glycemic screening regardless of age.
• Obstructive sleep apnea and mood disorders (depression, anxiety, eating disorders), which the International PCOS Guideline directs clinicians to screen for.
• Pregnancy complications: preeclampsia and preterm birth.

PCOS — treatment complications

• Ovarian hyperstimulation syndrome (OHSS) after gonadotropins/IVF — emergency. VEGF-mediated capillary leak causes ascites, hemoconcentration, oliguria, and VTE.
• Multiple gestation (higher with gonadotropins than letrozole); hyperkalemia with spironolactone; B12 deficiency and lactic acidosis with metformin; VTE with estrogen-containing contraceptives.

Endometriosis — disease complications

• Infertility from adhesions, distorted tubo-ovarian anatomy, and an inflammatory peritoneal milieu.
• Endometrioma rupture or ovarian torsion — emergency: sudden severe unilateral pain with peritoneal signs; torsion shows absent/decreased Doppler flow.
• Ureteral obstruction with silent hydronephrosis from deep infiltrating disease — limb of kidney loss; and bowel obstruction from rectosigmoid implants.
• Catamenial pneumothorax from thoracic implants — cyclic dyspnea/chest pain at menses.
• Clear cell and endometrioid ovarian carcinoma: a small but real absolute increase; signal is a growing, solid/vascular component within a known endometrioma.

Endometriosis — treatment complications

• Hypoestrogenism from GnRH agonists/antagonists: vasomotor symptoms and bone mineral density loss — mitigated by add-back therapy.
• Diminished ovarian reserve after endometrioma cystectomy (healthy cortex is removed with the capsule); surgical menopause after BSO.

• Rotterdam = 2 of 3 (hyperandrogenism, oligo/anovulation, polycystic ovarian morphology) after excluding CAH, Cushing, prolactinoma, thyroid disease, and androgen-secreting tumors. An elevated LH:FSH ratio is supportive, not a diagnostic criterion — that is the classic distractor.
• Ultrasound is not required if the other two criteria are met, and the International PCOS Guideline says ovarian morphology should not be used to diagnose PCOS within about 8 years of menarche, because multifollicular ovaries are physiologic in adolescence.
• Very high testosterone or rapid virilization (voice deepening, clitoromegaly) points to an androgen-secreting ovarian or adrenal tumor, not PCOS — image, don't start an OCP.
• Single best next step in PCOS who wants pregnancy: weight loss if overweight, then letrozole for ovulation induction (ASRM) — not clomiphene, not metformin.
• Single best next step in PCOS with prolonged amenorrhea and then heavy bleeding: endometrial biopsy. Unopposed estrogen → hyperplasia → carcinoma is the association examiners test most.
• Endometriosis exam findings: uterosacral nodularity, a fixed retroverted uterus, and a tender adnexal mass. Imaging shows a "chocolate cyst"; laparoscopy shows "powder-burn" lesions; histology needs endometrial glands and stroma outside the uterus.
• Pain severity does not track disease stage, and laparoscopy is not the first step in a typical adolescent — ACOG supports an empiric trial of NSAIDs plus continuous combined hormonal contraception.
• CA-125 may be elevated but is neither diagnostic nor a screening test for endometriosis — a favorite trap answer.
• Cyclic pelvic pain with primary amenorrhea = obstructed outflow tract (imperforate hymen, transverse septum), not primary dysmenorrhea.