EndoAxis

The Key To Timing Your Testing

Dr. Liz Bartman

Did you know The timing of a hormone test can determine the therapeutic efficacy of your interpretation. The timing of hormone testing is crucial for accurate interpretation and effective hormone-focused treatment.

One common area of confusion is whether to assess hormones during the follicular or luteal phase of the menstrual cycle (for our cycling female clientele). At EndoAxis, we rely on luteal phase urinary hormone metabolite testing, as this phase provides the clearest insight into ovulation, progesterone-to-estrogen ratios, and overall ovarian and endometrial health.

Why The Luteal Phase

The corpus luteum, a transient endocrine tissue, forms only after ovulation (and the rupture of a follicle), and is the primary source of progesterone. Progesterone levels remain low during the follicular phase, making it unreliable for assessing hormone balance. The DUTCH test, which we interpret, is also calibrated for luteal-phase interpretation, typically around days 19-23 of a 28-day cycle (5-9 days before menstruation). This is the optimal window to evaluate hormonal equilibrium, enzyme function, and fertility potential.

When To Use Follicular Testing?

Day 3 blood testing does still have importance and value. The early follicular window is

best for assessing LH, FSH, prolactin, and anti-Müllerian hormone (AMH), which

reflect hypothalamic-pituitary-ovarian (HPO) axis function. Estrogen levels fluctuate significantly during the follicular phase due to FSH-driven aromatase (CYP19A1) expression, making it unreliable for assessing estrogen activity, although higher-than expected values of estradiol in the follicular phase can indicate estrogen dominance.

Testosterone can be collected at any phase of the cycle, but is best tested before 11am,

and fasting for accuracy (as eating can naturally bump up Sex hormone binding globulin

activity, and to gauge accurate free hormone ratios, we want to see the body’s baseline

levels for these hormones and binding proteins). Similarly, thyroid testing can be completed at any phase of the cycle, but again, earlier in the day reveals optimal activity, and fasting may also be advantageous for thyroid activity.

Key Takeaways

For a comprehensive hormone assessment:

Use day 3 testing for peptide hormones (LH, FSH, prolactin, AMH) to evaluate HPO function.
Use luteal-phase testing for sex hormone balance and enzymatic function related to fertility, ovarian and endometrial health.

Ideally: Collect your serum markers on day 3 (or between days 2-5) and collect your

urinary hormone activity on day 20 (or between days 19-23).

By aligning hormone testing with the menstrual cycle, we can ensure more accurate diagnoses and targeted interventions.

Dr. Liz Bartman

Director of Clinical Sciences and Education

Dr. Liz is a naturopathic doctor with over a decade’s worth of experience in functional medicine. She currently serves as the Director of Clinical Sciences and Education for an exciting new company called EndoAxis. Having worked in Urgent Care prior to opening her private practice, Dr. Liz is well-versed in conventional standards of care and enjoys bridging the gaps of treatments and research in both the conventional and functional fields to provide tailored, evidence-based therapies to her patients. She graduated from the National University of Naturopathic Medicine, followed by the completion of a 2-year residency in Portland, OR. She maintains a practice in Salem, OR with a focus on hormone optimization and graceful aging through an epigenetic and nutrigenomic lens. She is finalizing her advanced certification in genetics and genomic medicine through Stanford and has sought additional training to broaden her professional pursuits in areas including advanced functional nutrition, nutrigenomics, environmental health, and botanical research. Having previously worked as an educational consultant at Precision Analytical, she has educated and consulted with physicians from around the world on complex hormone cases and has spoken professionally about hormone health, environmental toxin impacts on health, and nutrigenomic medicine.