The Menstrual Cycle DECODED: Fertility, PCOS, and the New Science of Hormones

**Dr. Gabrielle Lyon** (0:00)
There's a heavy discussion on the menstrual cycle.

**Dr. Heidi van den Brink** (0:03)
Over the course of the menstrual cycle, we have two things going on in two different organs. We have what's happening in the ovaries, and that's the ovarian cycle, and then we have what's happening in the uterus, and that's the uterine cycle.

**Dr. Gabrielle Lyon** (0:14)
I have never read about it, but I don't even think that there's many people that study it.

**Dr. Heidi van den Brink** (0:18)
There really isn't data to suggest that diet can cure PCOS. There is no cure for PCOS right now.

**Dr. Gabrielle Lyon** (0:25)
What is the myth that you hear?

**Dr. Heidi van den Brink** (0:27)
You shouldn't eat fruit if you have PCOS, because it makes your insulin resistance worse. The data actually show the exact opposite.

**Dr. Gabrielle Lyon** (0:34)
There are challenges with fertility now. It seems now more than ever on both sides.

**Dr. Heidi van den Brink** (0:38)
In those women with regular menstrual cycles and obesity, the majority of those ovulations met the criteria for radial face defects. And that can certainly affect fertility. In our research, we consider sort of a normal window, age at menarche, which is a girl's very first period, to be between 10 and 15 years. When menarche occurs earlier, that's associated with a whole host of long-term health outcomes like obesity, type 2 diabetes, endometrial cancer.

**Dr. Gabrielle Lyon** (1:07)
Can you get pregnant while on your period?

**Dr. Heidi van den Brink** (1:09)
I've seen ovulation during menses. Now let me explain what that means.

**Dr. Gabrielle Lyon** (1:22)
You are a reproductive physiologist, and you are the only person that has studied the ovarian transition from being reproductively robust to menopause.

**Dr. Heidi van den Brink** (1:33)
The transition to menopause, yes. Under the supervision of Dr. Angela Barrowald, but yeah, I was the one doing the work.

**Dr. Gabrielle Lyon** (1:40)
Pretty incredible. Exactly why I wanted you on, because you have a unique perspective. And I'm gonna open with a banger of a question.

**Dr. Heidi van den Brink** (1:48)
Sure.

**Dr. Gabrielle Lyon** (1:49)
Can you get pregnant while on your period? Inquiring minds want to know.

**Dr. Heidi van den Brink** (1:54)
Yes. Okay, great. The short answer is, I don't know. But the long answer is, I've seen ovulation during menses. Now, let me explain what that means. So during my master's degree, while I was characterizing how the ovaries work during the transition to menopause, this involved, you know, bringing women in every other day, or Monday, Wednesday, Friday, I think was that protocol for six to eight weeks. And these were women who are 45 to 55 years old. One participant in particular, one thing that we found, I can go into this later if you'd like, is that we started to observe, specifically in this transition to menopause, follicles in the ovary growing at unexpected and unusual times. And right around the time of ovulation, those follicles that were growing at this unexpected time seemed to respond as well to that ovulation, not by ovulating themselves, but by continuing to grow and producing a lot of estrogen. So this one particular participant, she had a follicle that responded to this LH surge and continued to grow and produce estrogen. And then while she was menstruating, sort of the end of her luteal phase when she was menstruating, that follicle didn't regress, it ovulated. And we saw a subsequent rise in progesterone, so we had ultrasonographic and endocrine confirmation of ovulation, which was surprising to us.
And, you know, we've seen anecdotally in other publications looking at other life stages like adolescent, sort of atypical timing of reproductive hormones. So I think what we saw in the transition of menopause could also happen at other life stages. It just hasn't sort of been characterized in that same way.

**Dr. Gabrielle Lyon** (3:35)
What's compelling to me and as someone who has been consuming information, and I think a lot of our viewers and listeners, there's a heavy discussion on the menstrual cycle. But prior to this podcast, I had never heard of a uterine cycle. I had never thought of an ovarian cycle. And it made me think that there are probably different phases, which we know of the menstrual cycle, which I'd love for you to touch on. But what about these other cycles?

**Dr. Heidi van den Brink** (4:05)
When I teach the menstrual cycle to my students, I use menses to menses. So the start of one menstrual event, menses, to the other is one menstrual cycle. Over the course of the menstrual cycle, we have two things going on in two different organs, right? We have what's happening in the ovaries, and that's the ovarian cycle. And then we have what's happening in the uterus, and that's the uterine cycle. Would you like me to go through them?