Understanding Your Fertility Hormone Cycle: The HPOU Axis

How to Read Your Cycle

Learning to track and interpret your period is important for diagnostic purposes and as a way to track changes to your fertility cycle as you move through your treatment plan and the four stages.

If you’re struggling with getting or staying pregnant, then your cycle is most likely not going to match an optimized cycle template.

The value of understanding what an optimized cycle looks like is in seeing where your cycle doesn’t line up with the template and then looking for clues into why you’re not matching up.

Cycle Day 1

Cycle day one is the first day of your period.

Emotionally and intuitively it often feels like your period is the end of your cycle, but according to standard medical convention, the first day of bleeding, not including spotting, is considered the first day of a new hormone cycle and so we call this Cycle Day (CD) 1.

Ovulation

Ovulation occurs 14 days prior to CD 1 in an optimized cycle. To calculate when you ovulated you subtract 14 days from your total cycle length.

For example, in the stereotypical 28 day cycle, you would subtract 14 from 28 and assume that ovulation occurred on cycle day 14.

However, if you have a cycle that is longer or shorter than 28 days, your ovulation day will not fall on cycle day 14. In a 30 day, ovulation would likely occur on CD 17, and in a 26 day cycle, ovulation would likely be occurring on day 12.

As you can see, relying on math alone is problematic. Ovulation day will shift depending on how you count the days and whether you use simple subtraction or count the actual days on a calendar like in the example below.

To truly identify ovulation you will need to use multiple methods of observation.

In this example CD 1 is on the first of the month, followed by 3 more days of bleeding (4 day bleed).

The next period started on the first of the following month which gives a total cycle length if 30 days.

Counting back 14 days before the next period puts ovulation at approximately day 17.

It’s important to keep in mind that using math alone to try to pinpoint when your ovulation occurs is never the primary way you want to confirm ovulation.

We’re just using this general model to illustrate what an optimized cycle typically looks like.

Using the calendar alone you’re doing a lot of analyzing in hindsight. It’s a good way to track what happened, but not an effective tool for predicting what’s going to happen.

This hormone cycle can very easily be thrown off by a multitude of factors including stress, medication, travel, etc., so it’s important to track other indicators of ovulation such as your cervical fluid changes, inito or Mira data, and BBT (which is also more of a confirmation metric than a predictor, but provides diagnostically significant information from an Eastern Medicine perspective).

Total Cycle Length

Total Cycle Length is the number of days from the first day of your period (spotting not included) to the day before your next period starts.

Determining Follicular Phase Length

The Follicular Phase is where the length of your cycle can vary. The length of your follicular phase is determined by how long it takes your body to go from CD 1 (first day of your period) to ovulation.

There are many factors that can influence this process including impaired receptivity of the follicles to FSH, impaired pituitary production of FSH, impaired estrogen feedback to the pituitary, insulin resistance, and chronic inflammation.

Supporting proper hormone signaling and responsiveness in the follicular phase is vital to ensuring optimal egg quality, proper corpus luteum formation, and progesterone production sufficient to stabilize your uterine lining and sustain early embryo development.

Determining the Length of Your Luteal Phase

Your Luteal Phase is the time between ovulation and your subsequent period. In an optimized cycle, the luteal phase is always 12-14 days. If your luteal phase is not consistently lasting 12-14 days, that can be indicative of specific pathologies, typically involving either insufficient progesterone production by the corpus luteum, or impaired receptivity of the endometrium to progesterone resulting in early destabilization of the lining.

If you have a short luteal phase or labs show low progesterone (keep in mind that it’s key that progesterone labs are done 7 days post ovulation - not necessarily CD 21), it can be tempting to think that supplemental progesterone will fix the issue.

Progesterone supplementation can be helpful in early pregnancy if you do conceive and have a history of low progesterone, however simply supplementing with progesterone will not have any effect on follicle, egg, or corpus luteum development in cycles when you’re trying to conceive.

It’s also important to note that if you begin taking progesterone too early — for example before you ovulate, based on the assumption that you’re ovulating on a certain day, but without confirming ovulation has actually occurred — you will likely delay or suppress ovulation.

To truly improve your progesterone production, the focus must be on improving follicle and egg development in the first half of the cycle by ruling out and identifying the specific factors impacting your hormone cycle.