How Adthyza works in your body explained in plain English. Learn its mechanism of action, onset time, and how it compares to other thyroid meds.
If your doctor prescribed Adthyza (or a similar natural desiccated thyroid medication), you might be wondering: what does this drug actually do once I swallow it? How does it fix what's wrong with my thyroid?
This guide explains how Adthyza works in plain, everyday language — no medical degree required. We'll cover what happens in your body, how long it takes to work, and what makes it different from other thyroid medications.
Think of your thyroid gland as your body's thermostat. It sits at the base of your neck and controls how fast or slow nearly every system in your body runs — your metabolism, your heart rate, your body temperature, your energy levels, even how fast you think.
When your thyroid is underactive (hypothyroidism), it's like your thermostat is set too low. Everything slows down. You feel tired, cold, foggy, and sluggish. Your body gains weight more easily and has trouble recovering.
Adthyza works by giving your body the exact hormones your thyroid isn't making enough of. Specifically, it provides:
Because Adthyza is made from real porcine (pig) thyroid glands, it naturally contains both T4 and T3 in a ratio similar to what a healthy human thyroid produces. When you take your daily tablet, those hormones enter your bloodstream through your digestive system and get to work doing what your own thyroid can't.
This is one of the most common questions, and the answer has two parts:
Because Adthyza contains T3 (the active hormone), some patients notice improvements in energy and mental clarity within the first 1-2 weeks. This is one reason many patients prefer NDT over synthetic T4-only medications — the T3 component can provide a faster boost.
It typically takes 4-8 weeks of consistent dosing for your thyroid levels to fully stabilize. This is why your doctor will check your blood work (TSH, Free T4, Free T3) about 6 weeks after starting or changing your dose. Full symptom relief — including improvements in weight, skin, hair, and mood — often takes 2-3 months.
Most patients don't land on their perfect dose right away. Starting at 32.5 mg/day and increasing by 16.25 mg every 2-3 weeks is typical. Each adjustment restarts the 4-8 week clock for that new dose to fully take effect. Be patient with the process — getting the dose right is more important than getting there fast.
The two hormones in Adthyza have different lifespans in your body:
The combination of a fast-acting hormone (T3) and a slow, steady one (T4) is what makes NDT medications like Adthyza feel different from T4-only drugs. Many patients describe feeling more "even" and natural on NDT because they're getting both hormones, rather than relying entirely on their body's ability to convert T4 to T3.
The biggest difference: Levothyroxine provides only T4, while Adthyza provides both T4 and T3.
With Levothyroxine, your body has to convert all the T4 into T3 on its own. Most people do this conversion just fine. But some patients — estimates suggest 10-15% of hypothyroid patients — don't convert T4 to T3 efficiently. These patients often feel better on an NDT medication or a combination therapy that provides T3 directly.
Levothyroxine is synthetic (made in a lab), while Adthyza is derived from animal tissue. Both are effective, but they're fundamentally different approaches.
Both are NDT medications with the same active hormones (T4 + T3 from porcine thyroid). The differences are in the inactive ingredients (fillers, binders, coatings) and the manufacturer. Some patients find they feel slightly different on one brand versus another — this usually comes down to how the inactive ingredients affect absorption.
With Adthyza discontinued, Armour Thyroid (made by AbbVie) is the most well-known remaining NDT option. For a full comparison, see our Alternatives to Adthyza guide.
Cytomel is a synthetic T3-only medication. It's sometimes prescribed alongside Levothyroxine for patients who need extra T3. The difference from Adthyza is that Cytomel provides no T4 — it's pure active hormone, which means it works fast but doesn't last as long and needs to be carefully dosed.
For those who want a bit more detail on the mechanism: thyroid hormones (T3 in particular) work at the cellular level. T3 enters your cells, crosses into the nucleus, and binds to specific proteins called thyroid hormone receptors. Once bound, these receptors activate or suppress specific genes that control:
This is why thyroid hormones affect virtually every system in your body — and why getting the dose right matters so much.
Adthyza works by replacing the thyroid hormones your body can't make on its own, providing both T4 and T3 in a natural combination. It's a straightforward concept — your thyroid is underperforming, so you supplement what's missing — but the dual-hormone approach is what set NDT medications apart from synthetic T4-only options.
Even though Adthyza has been discontinued, understanding how it worked can help you have better conversations with your doctor about alternatives. Whether you switch to Armour Thyroid, NP Thyroid, or a synthetic combination, the goal is the same: getting your T4 and T3 levels where they need to be so you feel like yourself again.
Need help finding your thyroid medication? Medfinder can help you check pharmacy availability near you.
You focus on staying healthy. We'll handle the rest.
Try Medfinder Concierge FreeMedfinder's mission is to ensure every patient gets access to the medications they need. We believe this begins with trustworthy information. Our core values guide everything we do, including the standards that shape the accuracy, transparency, and quality of our content. We’re committed to delivering information that’s evidence-based, regularly updated, and easy to understand. For more details on our editorial process, see here.
%2C%20Color%3DOriginal.png)
