Thyroid function and hypothyroidism: why current diagnosis and treatment fall short for many, and how new approaches are transforming care | Antonio Bianco, M.D., Ph.D.

**Peter Attia** (0:11)
Hey everyone, welcome to the Drive podcast. I'm your host, Peter Attia. This podcast, my website and my weekly newsletter all focus on the goal of translating the science of longevity into something accessible for everyone. Our goal is to provide the best content in health and wellness, and we've established a great team of analysts to make this happen. It is extremely important to me to provide all of this content without relying on paid ads. To do this, our work is made entirely possible by our members, and in return, we offer exclusive member-only content and benefits above and beyond what is available for free. If you want to take your knowledge of this space to the next level, it's our goal to ensure members get back much more than the price of a subscription. If you want to learn more about the benefits of our premium membership, head over to peterattiamd.com/subscribe. My guest this week is Dr. Antonio Bianco. Antonio is a physician scientist and an internationally recognized expert in thyroid physiology and metabolism. He is currently serving as the Senior Vice President and Dean at Interim of the John Sealy School of Medicine and Chief Research Officer at UTMB. He previously served as the President of the American Thyroid Association. He spent decades studying how thyroid hormones affect every cell in the body, with particular focus on the enzymes called deiodinases that activate or deactivate these hormones at the tissue level. He is also the author of Rethinking Hypothyroidism, which explores the science controversies and patient experiences surrounding thyroid hormone replacement therapy. In this episode, we discuss the fundamental biology of thyroid hormone production, conversion and action throughout the body, how the deiodinase enzymes regulate local thyroid hormone activity and why that matters for interpreting lab results, the limitations of using only TSH as a marker of thyroid function, and what's often missed in clinical practice, combination therapy, that is to say T3 and T4, versus standard levothyroxine or T4 treatment, the role of genetics, tissue sensitivity and individual variability around thyroid hormone metabolism, how hypothyroidism affects energy, mood, metabolism and cognitive function, the complex relationship between thyroid hormones and mitochondrial efficiency, cardiovascular health and longevity, and why some patients continue to feel unwell despite quote unquote normal thyroid lapse and how future research could reshape treatment approaches. So without further delay, please enjoy my conversation with Dr. Antonio Bianco.
Tony, thank you so much for making the trip up to Austin.

**Antonio Bianco** (2:57)
My pleasure.

**Peter Attia** (2:58)
I guess Calveson's not that far, huh?

**Antonio Bianco** (3:00)
No, it's three hours. It was pretty easy last night.

**Peter Attia** (3:04)
So you're the Dean of the Medical School there.

**Antonio Bianco** (3:06)
That's right.

**Peter Attia** (3:06)
You're running a lab. Tell me a little bit about what your research focuses on and maybe even what got you interested in studying the thyroid system.

**Antonio Bianco** (3:15)
Well, my research right now is trying to understand what thyroid hormone does. And by understanding what it does in different tissues, we will be able to serve patients that don't have sufficient thyroid hormone, patients with hypothyroidism. So we go at the level of the tissue level. So what does it do in the liver? What does it do in the heart? But then we go into the cell level and we are currently looking at how thyroid hormone affects the folding of the chromatin, because how it does it regulates gene expression. Basically, that's how T3 or thyroid hormone acts. By regulating different genes and because the genes are basically the essence of the cell functioning, by regulating the expression of those genes, it changes the way the cell behaves. And that has an important consequence for the whole tissue and for the organ and for the body.

**Peter Attia** (4:08)
So maybe let's start with the stuff that is largely known about the thyroid. I'll say a few things just to get us pointed in the right direction, but obviously I want you to correct me and or take us into a little bit more depth. I suspect many people know that they have a gland that sits over the voice box called the thyroid gland. That's probably what most people know. Most people also probably know that it produces a hormone. Some people might know that that hormone is actually inactive, abbreviated T4, because it has four iodines on it. And that now we're getting maybe past what most people would know. But enzymes in the body take one of those iodines off and make an active form of that hormone that we abbreviate T3. And I suspect that a number of people watching or listening realize that that hormone is very important. And it has properties that regulate energy expenditure, body temperature, mood, sleep, all sorts of things. I think the final thing I'll say that is probably somewhat common knowledge is that it is not entirely uncommon that some people don't seem to make enough of that hormone for one reason or another. We're going to talk about all of these things, of course. And that as a result of that, they have to supplement that hormone. And that condition could be referred to as hypothyroidism. And there are many people listening to us. I would venture that there are tens of thousands of people listening to us right now that would identify as having hypothyroidism and that are taking some form of thyroid replacement. Our objective today is to make sense of this whole thing because there are so many different ways that people think about how to replace that hormone. There are so many different ways that people think about how to diagnose the condition. And it seems that it is a much more complex endocrine situation than the other major systems we think about. It doesn't seem very difficult to understand what low testosterone is. You have a very simple assay. You understand the symptoms quite well. Replacing it is quite simple. It's very different here. So with that said, let's go back to that meta level. Layer on as much detail as you'd like about this gland that sits here and what it's doing.