Table 1:

Initial investigations and differential diagnoses for polycystic ovarian syndrome

TestResultsAlternative diagnosesNext steps
Expected results for patient with PCOSResults for a patient with an alternative diagnosis
ProlactinNormalMarkedly elevatedPituitary tumour
  • Repeat early morning, fasting prolactin

  • Test macroprolactin

  • Consider pituitary MRI

  • Referral to endocrinology

  • Repeat TSH

  • Test free T4

  • Consider levothyroxine supplementation

  • Consider referral to endocrinology

  • Repeat TSH

  • Measure T3/T4, refer to endocrinology

FSH, LH and estradiolNormal–high LH and normal FSH in the context of low follicular phase estradiolHigh FSH and LH in the context of low follicular phase estradiolPOI
  • Repeat test in 4 wk

  • Refer to gynecology or endocrinology

Low FSH, LH and estradiolHypogonadotropic hypogonadism
17-OHPNormalElevatedNon-classic adrenal hyperplasia
  • Refer to endocrinology

Calculated free testosterone, total testosterone and free androgen indexNormal–mildly elevatedMarkedly elevated total testosterone (> 5.2 nmol/L) (14)Ovarian or adrenal tumour
  • Transvaginal ultrasonography

  • Adrenal CT or MRI

  • Refer to endocrinology or gynecologic oncology

AndrostenedioneNormal–mildly elevatedMarkedly elevatedNon-classic adrenal hyperplasia or possible adrenal tumour
  • Refer to endocrinology

Dehydroepiandrosterone sulfateNormal–mildly elevatedElevated (> 18.9 μmol/L) (14)Adrenal tumour
  • Adrenal CT or MRI

  • Refer to endocrinology

Transvaginal ultrasonographyPCOM (≥ 10 mL ovarian volume or ≥ 20 follicles in either ovary)Ovarian tumour
  • Refer to gynecology

Anti-müllerian hormoneTypically greater than 34 pmol/L (15)UndetectablePOI (if age < 40 yr)
  • Refer to gynecology or endocrinology

LowAge-related decline in ovarian reserve
  • Note: CT = computed tomography, FSH = follicle-stimulating hormone, LH = luteinizing hormone, MRI = magnetic resonance imaging, PCOM = polycystic ovarian morphology, PCOS = polycystic ovarian syndrome, POI = premature ovarian insufficiency, TSH = thyroid-stimulating hormone, 17-OHP = 17-hydroxyprogesterone, β-hcg = β-human chorionic gonadotropin.