Laboratory Values Typically Out of Range in PCOS Diagnosis
The most common laboratory abnormalities in PCOS include elevated LH/FSH ratio (>2), elevated total testosterone (>2.5 nmol/L), low progesterone (<6 nmol/L), and markers of insulin resistance such as abnormal glucose/insulin ratio (>4). 1
Key Hormonal Abnormalities
Gonadotropins
- LH/FSH ratio: Often elevated >2 in PCOS patients 1, 2
- LH levels: Frequently elevated (>11 IU/L) 1
- FSH levels: Usually normal or slightly decreased 3
Androgens
- Total testosterone: Most frequently abnormal marker (elevated >2.5 nmol/L in 70% of PCOS cases) 1, 4
- Free testosterone: Typically elevated 1, 5
- Androstenedione: Elevated (>10.0 nmol/L) in approximately 53% of cases 1, 4
- DHEAS: May be elevated, particularly in younger women (>3800 ng/ml for ages 20-29, >2700 ng/ml for ages 30-39) 1
Other Sex Hormones
- Progesterone: Low mid-luteal phase levels (<6 nmol/L), indicating anovulation 1
- Sex hormone-binding globulin (SHBG): Often decreased, especially in obese patients 2, 5
Metabolic Parameters
Insulin Resistance Markers
- Glucose/insulin ratio: Decreased (<4), suggesting reduced insulin sensitivity 1, 2
- Fasting glucose: May be elevated (>7.8 mmol/L) 1
- Fasting insulin: Often elevated 5
Clinical Pearls and Pitfalls
- Most sensitive single marker: Total testosterone is the most frequently abnormal biochemical marker (70% sensitivity) 4
- Combination testing: Using testosterone, androstenedione, and LH in combination increases detection to 86% of PCOS cases 4
- LH/FSH ratio limitations: While traditionally emphasized, this ratio has lower sensitivity (41-44%) than previously thought 4
- Timing matters: Hormone levels should be measured between days 3-6 of the menstrual cycle for accurate assessment 1
- Assay variability: Different laboratory methods can yield significantly different absolute values, particularly for gonadotropins 4
- Obesity impact: Obesity affects hormone levels in PCOS, particularly decreasing SHBG levels 5, 6
Recommended Laboratory Panel for PCOS Diagnosis
First-line tests:
- Total testosterone
- Free testosterone
- LH and FSH (with ratio calculation)
- Progesterone (mid-luteal phase)
- Thyroid-stimulating hormone (TSH)
- Prolactin 2
Additional metabolic assessment:
- Fasting glucose/insulin ratio
- Lipid profile
- 2-hour 75g oral glucose tolerance test (particularly for BMI >25 kg/m²) 2
Further testing as indicated:
Remember that laboratory findings must be correlated with clinical features and ultrasound findings for proper PCOS diagnosis according to Rotterdam criteria, as no single test is diagnostic 2, 7.