Male Fertility and Sperm Health: What Your Sex Drive and Testosterone Really Mean | Dr. Michael Eisenberg

**Dr. Gabrielle Lyon** (0:00)
Are there any sex habits or behaviors that can reduce fertility? Is low libido a sign of poor sperm quality? What about the use of GLP-1s? How does that look from a male perspective? Does, say, looking at increase or decrease sperm quality or volume, how do we define male infertility?

**Dr. Michael Eisenberg** (0:19)
It's a good question. I mean, ultimately, fertility is a team sport, and so it's sort of defined at a couple level, so trying for a year and not getting pregnant. When we look at male, you know, sometimes when couples are trying to conceive and are not, you know, we worry, is it a male problem? Is it a female problem? Is it both? So, usually when we talk about male fertility, we define it in terms of semen quality.

**Dr. Gabrielle Lyon** (0:40)
I know that you're really at the forefront is male infertility, and it's a real problem, and it's very impactful for people, and all joking aside from positions and all of that, that it can really affect people's lives. Dr. Eisenberg, welcome to the show.

**Dr. Michael Eisenberg** (1:01)
Thank you so much for having me.

**Dr. Gabrielle Lyon** (1:03)
Now, there is a lot of conversation about infertility, sex, testosterone. I mean, I think that you are at the forefront of changing the trajectory of our health, because again, sexual health is, it's a dual role.
One of the things that has been really on my mind is this idea of performance enhancing medications. And what do I mean by that? Metformin, which you published a really high-impact study in a high-impact journal, which changed how we think about metformin. A lot of people were using metformin for longevity. But perhaps it does have an impact on sperm quality, fertility.

**Dr. Michael Eisenberg** (1:46)
Yeah. So that was a study that we did a few years ago. I'll give you the back story. But just for all your listeners and your viewers, essentially what we showed is that men that took metformin, their kids had a slightly higher risk of general birth defects.
If you think about how impactful that is, when medications get approved, they look at common endpoints. They look at any risks, side effects, things like that. But there's been such a change in demographics. Parents are getting older, fathers are getting older, and a lot of these medications are very much grandfathered in. And so we don't know really the reproductive effects of a lot of these medications. So for metformin specifically, when we're looking at it, you kind of think about why you take it and then what it does. And generally what we say is that anything that's good for your heart is going to be good for fertility. That's why we talk about diet, exercise, all those sorts of things. And so metformin, you know, generally if it's helping with blood sugar control, helping with diabetes, we think it should be beneficial. But there may be some effects. And so when we did this study, this was like a large cohort study. It basically looked at all births in Denmark over a period of time. We were able to identify the men that took metformin, men that didn't. We also looked at men that took other diabetic medications. And we found this association between metformin and birth defects in their sons mostly.
And, you know, obviously, it's a very impactful finding. You know, a lot of people take metformin, you know, more and more now, you know, fathers are getting older, there's more comorbidities for the fathers, so there's going to be diabetic fathers. And so, you know, it was kind of frightening. We don't want to be alarmist. So we really want to do a lot of kind of other tests to make sure that this was a true association. So we compared other diabetic medications, insulin, others, we didn't see that pattern. We also looked when they were specifically taking metformin. And so, spermatogenesis, making a sperm, takes about two to three months. So that window of exposure is kind of just before conception. So we looked at men that were taking it earlier. We looked at men that took it during the pregnancy, after the conception was done, after delivery, all those times. And really the only time we saw this spike in risk was if they took it just before they and their partner conceived. So it did kind of strengthen that this was a true finding. Yeah.

**Dr. Gabrielle Lyon** (4:12)
I mean, I have a few questions. Now, obviously, those that were taking metformin, I'm assuming, were diabetic.

**Dr. Michael Eisenberg** (4:19)
Yeah. Yeah.

**Dr. Gabrielle Lyon** (4:20)
There's been a lot of use of metformin for longevity purposes. That's where this could really inform our decisions.