Morning Testosterone and SHBG Testing in Women
Obtaining testosterone levels in women in nonresearch settings is not recommended, and therefore timing of collection (morning vs. other times) is generally not clinically relevant for routine practice. 1
Guideline-Based Recommendation
The HIV Medicine Association of the Infectious Diseases Society of America explicitly states that obtaining testosterone levels in women in nonresearch settings is not recommended (strong recommendation, low quality evidence). 1 This guideline specifically recommends morning serum testosterone levels only for adult men with symptoms such as decreased libido, erectile dysfunction, reduced bone mass, or low trauma fractures. 1
When Testing May Be Considered
If testosterone testing is pursued in women despite guideline recommendations against routine testing, the following considerations apply:
Timing of Collection
- Morning collection (8:30 AM) yields slightly higher testosterone levels than afternoon collection (1:30 PM) in women, with mean levels of 23.4 ± 12.4 ng/dL vs. 21.7 ± 12.9 ng/dL respectively (p=0.03). 2
- The diurnal variation in women is relatively small compared to overall variability, so reference ranges can be applied irrespective of the day in the menstrual cycle or time of day the sample is taken. 3
- Morning fasting samples are preferred when accurate measurement is needed, consistent with general principles for hormone testing. 4, 5
SHBG Measurement
- SHBG should be measured alongside testosterone to calculate the free testosterone index (ratio of total testosterone/SHBG), as this provides better assessment of androgen status than total testosterone alone. 6
- SHBG levels remain relatively stable across age ranges in premenopausal women (reference range 18-86 nmol/L for a 30-year-old woman). 3
- A free testosterone index <0.3 indicates hypogonadism. 6
Measurement Methodology
If testing is performed:
- Use liquid chromatography-tandem mass spectrometry in a laboratory certified by the CDC's Hormone Standardization Program, as immunoassays lack sufficient sensitivity for accurately measuring the low testosterone concentrations found in women. 4, 7
- Free testosterone should ideally be measured by equilibrium dialysis method if needed. 4, 5
- For premenopausal women, reference ranges for a 30-year-old are: total testosterone 15-46 ng/dL, free testosterone 1.2-6.4 pg/mL, and bioavailable testosterone 1.12-7.62 ng/dL. 3
Critical Caveats
- Most immunoassay-based methods used in clinical laboratories are inadequate for measuring testosterone in women due to insufficient low-end sensitivity, leading to inaccurate results. 7
- The clinical utility of testosterone measurement in women remains controversial and limited due to lack of well-established diagnostic criteria for female androgen deficiency. 7
- Clinical diagnosis must correlate laboratory values with symptoms, not rely on laboratory values alone. 6