Is a drop in progesterone (P4) levels from 196.6 to 167.4 at 14 days past late evening luteinizing hormone (LH) surge and 13 days past morning LH peak indicative of luteal phase wind down in a female of reproductive age?

E1G Drop at 14 Days Post-LH Surge: Normal Luteal Phase Wind Down

Yes, this estrone-3-glucuronide (E1G) drop from 196.6 to 167.4 at 14 days past LH surge represents normal luteal phase wind down, not luteal phase deficiency. 1

Understanding Normal Luteal Phase Hormone Patterns

Progesterone and estrogen secretion during the luteal phase is episodic and correlates closely with LH pulses, meaning relatively low mid-luteal hormone levels can occur in the course of a totally normal luteal phase. 1 This physiologic variation is critical to understand when interpreting single measurements.

Key Timing Considerations

• Progesterone normally peaks approximately 8 days after the LH surge 1
• At 14 days post-LH surge (13 days post-peak), you are well past the mid-luteal phase and approaching the late luteal phase 1
• The corpus luteum naturally begins to regress if pregnancy has not occurred, leading to declining hormone levels 1

Why This Is NOT Luteal Phase Deficiency

Do not diagnose "luteal phase deficiency" based on declining hormone levels in the late luteal phase—this represents normal corpus luteum regression. 2 The critical distinctions are:

Actual Luteal Phase Deficiency Criteria

• Clinical LPD: Luteal phase duration ≤10 days 3, 4
• Biochemical LPD: Mid-luteal progesterone ≤5 ng/mL (or <6 nmol/L for anovulation) 2, 4
• Anovulation marker: Progesterone <6 nmol/L during the mid-luteal phase indicates anovulation, not inadequate corpus luteum function 2

Your Situation

• You are at 14 days post-LH surge, which indicates a luteal phase duration that has already exceeded 10 days 3
• Your E1G levels (167.4) are declining from a peak, which is expected in late luteal phase 1
• The pattern shows normal corpus luteum formation and function followed by expected regression 1

Common Pitfall to Avoid

The most critical error is measuring hormones at the wrong time and misinterpreting late luteal phase decline as pathology. 2 Proper timing requires:

• Mid-luteal progesterone measurement should occur approximately 7-8 days after ovulation (around day 21 of a 28-day cycle) 2, 1
• Late luteal measurements (day 14 post-LH surge) will naturally show declining values as the corpus luteum regresses 1
• Single measurements can be misleading due to episodic secretion patterns 1

When to Actually Investigate

Investigation for underlying causes is warranted only when: 2

• Mid-luteal progesterone is <6 nmol/L (indicating anovulation) 2
• Luteal phase duration is consistently ≤10 days 3, 4
• Recurrent patterns across multiple cycles 4

In such cases, workup should include LH, FSH, testosterone, prolactin, androstenedione, DHEAS, and pelvic ultrasound to assess for PCOS, hypothalamic amenorrhea, or hyperprolactinemia. 2