Dynamics of serum testosterone during the menstrual cycle evaluated by daily measurements with an ID-LC-MS/MS method and a 2nd generation automated immunoassay.
Level 3 - non-randomized controlled study
Prospective longitudinal observational study tracking daily biomarkers in a single cohort
PubMed 23127814 · doi:10.1016/j.steroids.2012.10.010
What was done
Researchers measured serum testosterone daily across the complete menstrual cycle in 25 healthy women characterized by biochemical and physical examination. Daily concentrations were quantified using a validated isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) method and compared against an automated second-generation immunoassay (ARCHITECT 2nd Generation Testosterone).
What was found
The ID-LC-MS/MS method closely matched a published reference standard (y = 1.007x - 0.056 nmol/L; r = 0.9998). The automated immunoassay showed strong correlation with ID-LC-MS/MS (y = 1.095x + 0.104 nmol/L; r = 0.9031) but exhibited a persistent positive bias. Established reference intervals were 0.30–1.69 nmol/L (8.7–48.7 ng/dL) for ID-LC-MS/MS and 0.50–2.00 nmol/L (14.4–57.7 ng/dL) for the immunoassay. While testosterone concentrations were significantly higher mid-cycle overall, an ovulatory peak was not discernible in every participant, and random day-to-day variation exceeded cycle-dependent fluctuations.
Why it matters
Because normal day-to-day fluctuations exceed mid-cycle variations, a single random testosterone blood test cannot reliably capture a woman's true testosterone status. It also confirms that modern second-generation immunoassays track mass spectrometry profiles adequately despite a slight positive calibration bias.
Limits
The sample size was small (n = 25), and all participants were healthy women, limiting direct applicability to clinical populations with hyperandrogenism or ovulatory disorders. Only a single menstrual cycle per woman was evaluated.
Cited by
- supports Unlike men who experience a 24-hour diurnal testosterone rhythm, women experience a peak in testosterone in the week just prior to ovulation.