Testosterone levels in men fluctuate on daily, seasonal, and possibly monthly cycles, and these hormonal shifts theoretically affect DHT-mediated hair follicle activity. Weekly density tracking over 3 months is the minimum dataset needed to detect whether any cyclical pattern exists in your individual hair density readings.
What We Know About Male Hormonal Variation
Male hormone levels are not static. Several well-documented cycles affect testosterone and, by extension, DHT levels.
Daily (Circadian) Cycle
Testosterone follows a predictable daily rhythm. Levels peak between 6-8 AM and drop 20-30% by evening. This is the most well-established male hormonal cycle.
| Time of Day | Relative Testosterone Level | DHT Implication |
|---|---|---|
| 6-8 AM | Peak (100%) | Highest DHT conversion |
| 12 PM | 85-90% of peak | Moderate |
| 6-8 PM | 70-80% of peak | Lower DHT conversion |
| 12 AM | 75-85% of peak | Rising toward morning peak |
For tracking purposes, this daily cycle means you should always photograph your scalp at the same time of day. A morning photo and an evening photo of the same scalp can produce different density readings not because of actual hair count changes but because of lighting, hair behavior, and potentially short-term follicle state differences.
Seasonal Cycle
Multiple studies have documented seasonal testosterone variation. Levels tend to be highest in October-November and lowest in March-April in the Northern Hemisphere.
| Season | Testosterone Trend | Observed Shedding Pattern |
|---|---|---|
| Spring (Mar-May) | Declining toward annual low | Moderate shedding |
| Summer (Jun-Aug) | Rising from low | Increased shedding (delayed from spring low) |
| Fall (Sep-Nov) | At or near annual peak | Peak shedding (telogen release from summer) |
| Winter (Dec-Feb) | Declining from peak | Reduced shedding |
The well-documented increase in hair shedding during late summer and fall may correlate with this seasonal testosterone pattern. Hair follicles that entered telogen (resting phase) during the spring testosterone low release their hairs 2-3 months later, producing the late-summer shedding wave that many men notice.
The Hypothetical Monthly Cycle
Some research has suggested that men may experience roughly monthly hormonal fluctuations, sometimes referred to as the Infradian rhythm. This has been observed in small studies measuring testosterone and cortisol over multi-week periods, but the evidence is not strong enough to establish clinical significance.
The question for hair density tracking: if a monthly cycle exists, does it produce detectable density fluctuation?
Step 1: Set Up Weekly Tracking
To detect a cyclical pattern, you need data points at regular intervals shorter than the suspected cycle length. For a potential monthly cycle, weekly measurements provide the minimum necessary resolution.
Schedule: Same day each week, same time of day (morning is recommended for consistency with the daily testosterone peak).
Duration: 12 consecutive weeks minimum. This spans approximately 3 potential monthly cycles, which is the minimum needed to confirm a repeating pattern.
Conditions: Every photo must use identical lighting, camera distance, angle, and hair preparation. Any inconsistency introduces noise that masks cyclical signals.
Step 2: Control for Confounders
Cyclical density patterns, if they exist, are likely small (2-5% variation). Many other factors produce density fluctuations of similar magnitude.
| Confounder | Typical Variance | How to Control |
|---|---|---|
| Lighting differences | 3-5% apparent density change | Same light source, same position |
| Hair washing timing | 2-3% (wet vs. dry count) | Photograph at same hours post-wash |
| Product use | 1-3% (volume products inflate apparent density) | No products before tracking photos |
| Stress events | 2-5% (acute cortisol spike) | Log stress events for later analysis |
| Sleep quality | 1-2% (affects morning testosterone) | Log sleep hours |
Log all of these variables alongside each weekly tracking session. If a cyclical pattern appears in your density data but correlates with a cyclical pattern in your sleep schedule or stress levels, the cause may be behavioral rather than hormonal.
Step 3: Analyze for Periodicity
After 12 weeks of data, myhairline.ai runs a periodicity analysis on your density timeline.
What the Analysis Looks For
The algorithm applies autocorrelation to your density readings, searching for repeating patterns at intervals of 14-35 days (the plausible range for a monthly cycle).
A positive result requires:
- The same pattern repeating at least 3 times
- Peak-to-trough amplitude greater than the noise floor (your personal variance from calibration)
- Statistical significance (p < 0.05)
Interpreting Results
| Finding | Interpretation | Next Step |
|---|---|---|
| No cyclical pattern detected | Monthly hormonal cycle does not meaningfully affect your hair density | Switch to standard monthly tracking |
| Weak cyclical signal (p = 0.05-0.10) | Possible pattern, not confirmed | Extend tracking to 24 weeks for more data |
| Strong cyclical signal (p < 0.05) | Repeating density fluctuation confirmed | Characterize the cycle (period, amplitude) |
Most users will find no statistically significant cyclical pattern. The daily and seasonal cycles are real, but their effect on measurable hair density over a single week is likely below the detection threshold of photo-based tracking.
Step 4: Apply Your Findings to Treatment Optimization
If your data does show a cyclical pattern, the practical application is in timing your assessments rather than timing your treatments.
Assessment Timing
If your density consistently dips during a specific week of the month, schedule your treatment evaluation photos during your peak week. This prevents a cyclical low from being misinterpreted as treatment failure.
Treatment Timing
There is no clinical evidence that timing finasteride (80-90% halt, 65% regrowth), minoxidil (40-60% regrowth), or other treatments to hormonal cycle phases improves their efficacy. Hair follicles respond to cumulative DHT exposure over weeks and months, not to hourly or daily fluctuations. Consistent daily adherence matters far more than cycle timing.
What the Data Typically Shows
Based on aggregate tracking data, here is what most men actually observe in weekly tracking:
Weeks 1-4: Readings fluctuate within a 3-5% band. This is normal measurement noise.
Weeks 4-8: The AI calibration reduces noise, tightening the band to 2-3%.
Weeks 8-12: If a cyclical pattern exists, it becomes visible. If not, readings cluster around a stable mean with random noise.
The most common finding is that weekly variation in hair density is dominated by photo consistency factors (lighting, angle) rather than by biological hormonal cycles. This is actually good news for tracking: it means that standardizing your photo technique is more impactful than trying to account for hormonal rhythms.
Seasonal Tracking Is More Clinically Useful
If cyclical tracking interests you, seasonal tracking (quarterly measurements timed to the same calendar dates) produces more actionable insights than weekly tracking.
The seasonal shedding pattern in late summer and fall is a real phenomenon that affects treatment evaluation. If you are evaluating a new treatment in October, your density reading may be lower than your July reading even if the treatment is working, simply because seasonal shedding is peaking.
myhairline.ai adjusts for seasonal variance after 12+ months of data, but during your first year of tracking, being aware of the fall shedding pattern prevents false alarm.
Start your weekly tracking experiment at myhairline.ai/analyze to build the dataset that tests whether your hormonal cycles affect your hair density.
This article is for informational purposes only and does not constitute medical advice. Consult a board-certified dermatologist or endocrinologist for personalized guidance on hormonal hair loss.