At what phase of a regular menstrual cycle does a woman typically experience her lowest testosterone level?

Testosterone Levels During the Menstrual Cycle

In women with regular menstrual cycles, testosterone levels are lowest during the late luteal phase (approximately days 21-28), just before menstruation begins. 1, 2

Testosterone Fluctuation Pattern Across the Cycle

The menstrual cycle demonstrates a characteristic pattern of testosterone variation that differs from the more dramatic fluctuations seen with estrogen and progesterone:

Early Follicular Phase (Days 1-7)

• Testosterone levels begin to rise during the early follicular phase as the ovaries respond to increasing follicle-stimulating hormone 3
• This represents a recovery from the nadir reached in the late luteal phase 1

Mid-Cycle/Ovulation (Days 12-16)

• Testosterone peaks at mid-cycle, coinciding with the estrogen surge and ovulation 1, 4
• This peak occurs alongside elevated estradiol, luteinizing hormone, and sex hormone-binding globulin (SHBG) 1
• The mid-cycle elevation reflects increased ovarian testosterone production in response to rising gonadotropins 3

Luteal Phase (Days 17-28)

• Testosterone levels remain elevated during the early-to-mid luteal phase compared to the early follicular phase 1, 5
• Free testosterone levels progressively decline throughout the luteal phase, reaching their lowest point in the late luteal phase 2
• Total testosterone falls progressively during this time, with the most significant drop occurring just before menstruation 2

Important Clinical Considerations

Magnitude of Variation

• The overall variation in testosterone across the menstrual cycle is relatively modest compared to estrogen fluctuations 4
• Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), which is more accurate than older immunoassays, the changes are even smaller than previously reported 1
• Because the mid-cycle increase is small relative to overall variability, testosterone can be measured on any day of the cycle for clinical assessment 4

Measurement Methodology Matters

• Older radioimmunoassay methods showed only minor and irregular fluctuations, missing the true cyclical pattern 5
• Modern LC-MS/MS methods reveal that actual testosterone levels in women are lower overall than previously reported with immunoassays, but demonstrate clearer cyclical patterns 1
• High-performance liquid chromatography (HPLC) shows considerably greater testosterone concentrations in the luteal phase than follicular phase, a pattern missed by conventional RIA 5

Relationship to Other Hormones

• The testosterone pattern appears to reflect changes in both SHBG and estrogen levels across the cycle 1
• Progesterone may displace testosterone from its binding proteins during the luteal phase, affecting free testosterone levels 2
• While total testosterone may remain relatively stable, the percentage of free testosterone increases from follicular to luteal phase due to these binding protein changes 2

Clinical Pitfall to Avoid

Do not assume that timing of testosterone measurement is critical for diagnostic purposes in women with hirsutism or suspected androgen excess 3. The relatively small fluctuation in testosterone levels throughout the cycle means that a single measurement on any cycle day is sufficient for clinical assessment, unlike the situation with progesterone (which must be measured mid-luteal phase to confirm ovulation) 4.