Cycle Day 3 Hormonal Profile
The essential hormones to measure on cycle day 3 (or days 3-6) of the menstrual cycle are FSH, LH, estradiol, prolactin, TSH, and free T4, with testosterone and AMH added based on clinical presentation. 1
Core Hormone Panel and Timing
Measure the following hormones between cycle days 3-6 of the menstrual cycle:
- FSH (Follicle-Stimulating Hormone) 2, 3, 1
- LH (Luteinizing Hormone) 3, 4, 1
- Estradiol (E2) 2, 4, 1
- Prolactin 2, 1
- TSH and Free T4 1
Additional hormones based on clinical presentation:
- Testosterone (if hirsutism, virilization, or suspected PCOS) 3, 1
- AMH (Anti-Müllerian Hormone) (for ovarian reserve assessment) 2, 4, 1
- Progesterone (measured mid-luteal phase, not day 3) 3, 1
- DHEA-S (if hyperandrogenism suspected) 3, 1
Optimal Sampling Technique
For FSH and LH, obtain three blood samples 20 minutes apart and calculate the average for optimal accuracy. 3, 1 This approach minimizes the impact of pulsatile secretion and provides more reliable results than a single measurement.
Normal Reference Ranges for Reproductive-Age Women (Day 3)
FSH Reference Values
- Normal range: 3.3-9.5 IU/L (women aged 20-25 years) 5
- Normal range: 3.8-23.8 IU/L (women aged 40-45 years) 5
- Median early follicular: 7.14 IU/L (range 4.78-13.2 IU/L) 6
- Elevated FSH: >25 IU/L indicates premature ovarian insufficiency (POI) 2, 1
LH Reference Values
- Normal range: 0.2-1.7 (LH/FSH ratio) in early follicular phase 7
- Median early follicular: 7.14 IU/L (range 4.78-13.2 IU/L) 6
- LH/FSH ratio >2 suggests PCOS 3, 1
Estradiol (E2) Reference Values
- Normal range: 20.4-95.0 pg/mL (women aged 20-25 years) 5
- Normal range: 22.4-122.8 pg/mL (women aged 40-45 years) 5
- Median early follicular: 198 pmol/L (range 114-332 pmol/L) or approximately 54 pg/mL 6
- Low estradiol: <20-50 pg/mL with elevated FSH indicates ovarian insufficiency 2, 1
Prolactin Reference Values
Testosterone Reference Values
AMH Reference Values
- Normal/adequate reserve: >1 ng/mL 1
- Diminished reserve: <0.5-1 ng/mL 4, 1
- Lower limit in peak reproductive age: 51.7 pg/mL 5
Critical Diagnostic Patterns
Premature Ovarian Insufficiency (POI)
- FSH >25-35 IU/L (often 25-64 IU/L, average 37 IU/L) 2, 1
- Estradiol <20-50 pg/mL 2, 1
- AMH <0.5 ng/mL 1
- Repeat testing after 1 month to confirm 2
Polycystic Ovary Syndrome (PCOS)
- LH/FSH ratio >2 3, 1
- Testosterone >2.5 nmol/L 3, 1
- Normal or elevated AMH 1
- Low progesterone <6 nmol/L (anovulation) 3, 1
Functional Hypothalamic Amenorrhea
Hyperprolactinemia
Critical Pitfalls and Caveats
Discontinue hormonal contraception at least 3 months before testing. Combined estrogen-progestin contraception or antigonadotropic progestins will significantly suppress FSH levels and invalidate results. 2, 1
Avoid post-ictal prolactin sampling. In women with epilepsy, prolactin must be measured as a morning resting level, not after a seizure. 3, 1
Repeat borderline FSH elevations (25-35 IU/L) after 1 month. FSH levels can vary between cycles, particularly in women aged 40-45 years, where 22% may have normal values in one cycle and elevated values in the next. 5, 8
Estradiol >150-200 pg/mL on day 3 suggests mid-cycle surge or estradiol-secreting cyst, not true baseline follicular phase values. 2, 1
Day 2 or day 4 sampling is acceptable if day 3 is unavailable. FSH varies by approximately 14.8% (coefficient of variation) between days 2-4, while estradiol varies more widely at 31.1%. 8
Reference ranges are assay-specific. Different laboratory methods produce different absolute values; clinicians must use local reference ranges. 6, 5, 9