The Hormonal Relationship Between LH, PDG, and HCG

Getting pregnant fast can be trickier than it seems. Care, testing, and patience are key. It is normal for conception to take time, even when it is carefully planned!

According to our studies of 3,000 women who are trying to get pregnant, under 50% have been registered as pregnant after 9 months.

If you want to get pregnant sooner, it is very important to understand how your fertility hormones correlate to each other and how they can help you get pregnant faster.

Three important hormones to know during this process are:

1. Luteinizing hormone (LH): its surge signals that ovulation is about to happen and the egg is to be released

2. Progesterone: a hormone released by the corpus luteum which stimulates the uterus to prepare for pregnancy

3. Human chorionic gonadotropin (HCG): known as the "pregnancy hormone," its rise is the key sign of pregnancy

Tracking these hormones will allow you to understand your body, get pregnant faster, and avoid invasive fertility treatments.

The charts below will show you the progression of the three hormones before and after getting pregnant.

         

For many fertile women, LH levels will increase and reach peak (at between 25-45 mIU/mL) 24-36 hours before ovulation and drop after ovulation. Progesterone, and its urine metabolite PDG, will increase and reach peak (at above 5ug/mL) around 5 days after ovulation. If fertilization does not occur, progesterone levels will drop before the next period. Otherwise, levels remain high until the end of the pregnancy term. HCG levels will increase gradually after fertilization to a detection level (25 mIU/mL) after pregnancy and will stay high throughout.Tracking these three hormones at the right time will help you know when the best time to get pregnant is and to know when you are pregnant earlier.

Most women know that LH tests are commonly used as ovulation tests and that HCG tests are simply another name for pregnancy tests. However, many women don’t know about testing for progesterone. Women can confirm ovulation by monitoring their rise in progesterone with progesterone tests or with BBT (basal body temperature) tracking.  (Learn more about BBT here.)


Although LH levels will not remain high after pregnancy, note that the chemical makeup of HCG is very similar to that of LH. While pregnancy tests can tell the difference between LH and hCG, ovulation tests cannot. Therefore, an ovulation test may show a false positive result from a cross reaction f you have hCG levels that are at or above an LH test's detection sensitivity for LH at the very end of your cycle.

*However DO NOT use ovulation tests as a substitute for a pregnancy test.  They are not designed for this tracking, and it's just as likely that raised levels after a first peak could be a second peak!  Be sure to keep targeting sexual activity to any LH peaks that you have during your cycle, and learn more about multiple peaks here.*

Knowledge is power! Now that you understand the function and the importance of these three important fertility hormones, you can take charge of your fertility process!

Sources:

https://www.sciencedirect.com/science/article/pii/S0303720713005248

https://obgyn.onlinelibrary.wiley.com/doi/full/10.1111/aogs.12770

Updated August 24, 2020

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