Testosterone Levels Across the Menstrual Cycle
Testosterone levels are at their lowest during the early follicular phase (days 3-6) of a regular menstrual cycle, with levels rising at mid-cycle and remaining elevated during the luteal phase. 1
Timing of Testosterone Measurement
- For diagnostic purposes, testosterone should be measured during days 3-6 of the menstrual cycle (early follicular phase) when levels are at their baseline. 1
- This timing is recommended in clinical guidelines for evaluating reproductive endocrine disorders in women, as it provides the most consistent and lowest reference point. 1
Testosterone Fluctuation Pattern During the Cycle
Early Follicular Phase (Lowest Levels)
- Testosterone concentrations are at their nadir during the early follicular phase of the menstrual cycle. 2, 3
- Research using highly accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS) confirms that testosterone levels start low in the early follicular phase. 3, 4
Mid-Cycle (Peak Levels)
- Testosterone levels increase significantly during the mid-cycle period around ovulation. 2, 5, 3
- Median testosterone rises from early follicular baseline to peak at mid-cycle, with values ranging from 0.34 nmol/L (range 0.04-1.01) across the entire cycle. 2
- This mid-cycle elevation corresponds with the preovulatory surge in luteinizing hormone and follicle-stimulating hormone. 5
Luteal Phase (Elevated Levels)
- Testosterone concentrations remain significantly higher during the luteal phase compared to the early follicular phase. 2, 3
- Free testosterone levels also peak at mid-cycle and remain elevated in the mid-luteal phase. 3, 6
- Total testosterone falls progressively through the luteal phase, but remains above early follicular levels until the late luteal phase. 6
Clinical Implications
The relatively small magnitude of cyclical testosterone variation means that a single measurement during the early follicular phase is sufficient for clinical assessment. 5, 4
- Day-to-day variation in testosterone is actually higher than menstrual cycle-related variation, making the clinical relevance of these cyclical changes questionable. 4
- Guidelines for evaluating hirsutism, polycystic ovary syndrome, and other androgen-related conditions recommend measuring testosterone on days 3-6 of the cycle to standardize timing. 1
- Abnormal testosterone levels are defined as >2.5 nmol/L when measured during this early follicular window. 1
Important Caveats
- Not all androgens fluctuate with the menstrual cycle. Dehydroepiandrosterone (DHEA), 11-ketoandrostenedione, and 11-ketotestosterone remain stable throughout the cycle and do not show cyclical variations. 2
- Age significantly affects testosterone levels, with all androgens declining before menopause, requiring age-specific reference ranges for proper interpretation. 2
- Body mass index influences testosterone levels, with overweight women having lower median testosterone, DHEA, and 11-ketoandrostenedione levels than normal-weight women. 2
- In anovulatory cycles, testosterone shows random fluctuation with no well-defined pattern, unlike the predictable changes seen in ovulatory cycles. 5