Bovine vs. Porcine Thyroid

Today’s email comes straight from a question I got from a reader in my question box.

It surrounds the topic of thyroid support and supplementation.

You guys know I LOVE these kinds of questions, because there’s so much misinformation out there when it comes to thyroid optimization—and so many doctors have never even tried desiccated thyroid themselves, let alone gone beyond the mainstream guidelines.

So let’s get into it.

The Origin Story

Before the age of Big Pharma and all the shiny synthetic molecules, thyroid disorders were handled the old-fashioned way: by using the actual glandular extracts from animals.

For over a hundred years, desiccated thyroid—dried and powdered thyroid gland from animals—was the treatment for hypothyroidism.

Why? Because it works.

Desiccated thyroid contains not only the main hormones (T4 and T3) but also T1, T2, and even calcitonin—the co-factors and “supporting cast” that work synergistically in our bodies.

Unlike synthetic T4 (Levothyroxine), which is a one-note symphony, desiccated thyroid delivers a broad spectrum of what your thyroid would naturally produce.

Many people on just T4 monotherapy (the standard of care today) still feel sluggish, cold, or just “off,” even when their labs are “normal.”

The reason: they’re missing the critical elements found in natural glandular extracts—especially T3, the active thyroid hormone that your cells actually use.

Porcine vs. Bovine

Porcine thyroid extract is used in prescription desiccated thyroid brands, such as Armour, NP Thyroid, and Nature-Throid.

It’s standardized, regulated, and contains a consistent, predictable ratio of T4 to T3.

This is a game-changer for anyone who actually needs real hormone replacement.

These prescription forms are tested, batch-controlled, and deliver exactly what the label says—no more, no less.

Bovine thyroid, on the other hand, is usually found in over-the-counter supplements—often in the “glandular” or “ancestral nutrition” section.

It’s almost never standardized, meaning there’s no guarantee it contains active T4 or T3 at all.

In the US, if it’s sold as a supplement, it’s actually not allowed to contain measurable amounts of active thyroid hormone.

Sometimes it’s nothing more than dried-up cow thyroid tissue, with little or no hormonal effect.

Bottom line:

Porcine = pharmaceutical, standardized, effective for true hormone replacement.

Bovine = supplement, unreliable, probably not actually helping your thyroid hormone levels if you’re truly deficient.

The Science

Why do so many people feel better on desiccated thyroid compared to Synthroid or generic levothyroxine?

The science is actually pretty straightforward.

Your body doesn’t just need T4; it needs a balance of thyroid hormones.

Porcine desiccated thyroid typically provides a T4:T3 ratio of about 4:1, which is much closer to what the human thyroid produces than you might think.

It also includes minor thyroid compounds (T1, T2) and calcitonin—each playing a role in the full spectrum of thyroid function.

Synthetic T4-only therapy, on the other hand, relies on your body’s ability to convert T4 to T3.

But here’s the catch: a huge percentage of people—especially those with Hashimoto’s, chronic inflammation, or genetic issues—don’t convert efficiently.

So you wind up with “normal” lab numbers but still have all the classic low-thyroid symptoms.

Studies, including a big one in the New England Journal of Medicine (Hoang et al., 2013), have shown that patients prefer desiccated thyroid and often feel better on it—even when their blood work looks the same as with T4 alone.

The Dosing, Consistency, and Clinical Experience

If you’re using porcine desiccated thyroid (Armour, Nature-Throid, etc.), you’re getting a precise, pharmaceutical-grade product:

1 grain (60 mg) delivers about 38 mcg T4 and 9 mcg T3. It’s prescription, so every batch is tested and regulated for hormone content.

On the other hand, bovine desiccated thyroid supplements are all over the map.

Some have zero active hormone; others have trace amounts (sometimes enough to cause side effects, if you’re lucky or unlucky, depending on your situation).

These are NOT regulated or approved for treating hypothyroidism. If you want real hormone support, you simply can’t rely on these.

I can’t count the number of clients who “tried glandulars” from health food stores with zero result—only to feel like a brand new person when they switched to a proper, standardized porcine thyroid prescription.

Special Considerations

Now, a few nuanced points.

There are legit reasons why someone might prefer bovine over porcine thyroid, even with all the caveats.

If you have religious dietary restrictions (kosher, halal), pork-derived products might be off-limits.

In that case, a bovine product could make sense as a supplement—but just know you’re probably not getting any meaningful hormone activity.

On the other hand, if you have a true medical need for thyroid hormone, you’re always better off working with a practitioner to get a proper, standardized prescription—even if that means seeking a compounding pharmacy that can make bovine-derived thyroid (rare, but possible in some countries).

For most people, porcine is going to be the gold standard for effect and reliability.

Another point: some people believe bovine products are “cleaner” (grass-fed, organic, etc.), but unless they’re standardized and tested for active hormone, these are more marketing buzzwords.

What Should YOU Do?

If you’re truly hypothyroid or have persistent low-thyroid symptoms despite “normal” labs, desiccated thyroid can be a life-changer.

And if you want real results, stick to the standardized, regulated, porcine forms.

If you’re dabbling in supplements for general “glandular support,” bovine may have a place—but don’t expect miracles.

As always, do your own research, listen to your body, and don’t let “standard of care” dogma keep you feeling mediocre.

Best,

Hunter Williams