- Levothyroxine is first-line: Synthetic T4, precise and well-studied. It works well for most people and is the standard of care.
- Some don't feel well on it: A real subset stay symptomatic despite a normal TSH — often less efficient T4-to-T3 converters.
- The alternatives: T3/T4 combination therapy and desiccated thyroid (Armour, NP Thyroid) add active T3. Trials are mixed.
- Safety: Adding T3 needs proper dosing and monitoring, especially in older patients or those with heart concerns.
Here is the evidence, without the tribalism. This article is part of our guide to thyroid medicine.
What are the two options?
Levothyroxine is synthetic T4 — the storage form of thyroid hormone your body converts to active T3 as needed. It's precise, stable, inexpensive, and the most-prescribed thyroid medication in the world.
Desiccated thyroid extract (DTE) — brands like Armour Thyroid and NP Thyroid — is made from dried pig thyroid and contains both T4 and T3 in a fixed ratio. Sometimes called "natural thyroid," it has been used for over a century. There's also a middle path: synthetic T3/T4 combination therapy, which adds measured liothyronine (synthetic T3) to levothyroxine.
Why is levothyroxine first-line?
For most people with hypothyroidism, levothyroxine works well: it normalizes thyroid function and resolves symptoms, and its single-hormone design lets clinicians dose precisely and monitor with a simple blood test. Major thyroid societies endorse T4 monotherapy because it is effective, predictable, and well studied. If you feel good on levothyroxine, there's no reason to switch.
Why don't some people feel well on T4 alone?
Here's what the "just take your levothyroxine" camp sometimes glosses over: a real subset of patients continue to feel unwell — fatigue, brain fog, low mood — even when their TSH is textbook normal. One plausible explanation is less efficient conversion of T4 to active T3. For these patients, adding T3 (via combination therapy or DTE) is a reasonable thing to explore. Their experience isn't just imagination.
What do the trials show?
Randomized trials and meta-analyses comparing T3/T4 combination therapy or DTE against levothyroxine tell a nuanced story. Some patients report preferring combination or desiccated therapy and feeling better on it. But across studies, the benefit has not been consistently demonstrated on objective measures. DTE reliably produces higher T3 and lower T4 blood levels than levothyroxine; whether that translates into better quality of life depends on the study and the patient.
Because of this inconsistency, guidelines continue to recommend levothyroxine first while acknowledging that a supervised trial of combination therapy may be appropriate for patients who remain symptomatic. In other words: T4 first, but the door is open — with a clinician — for those who don't do well on it.
What are the safety considerations?
Adding T3 isn't free of trade-offs. T3 is more potent and shorter-acting, which can cause peaks and dips, and higher T3 exposure carries potential cardiovascular considerations — relevant for older patients or anyone with heart disease or atrial fibrillation risk. DTE also has a fixed T3:T4 ratio that doesn't match every individual's needs. None of this makes these options bad — it makes them options that need proper dosing and monitoring rather than casual self-switching.
What's the bottom line?
This isn't "natural versus synthetic" or "good versus bad." Levothyroxine is the proven starting point and the right fit for most people. For the minority who remain symptomatic despite normal labs, T3/T4 combination therapy or desiccated thyroid is a legitimate, evidence-informed next step — best done as a monitored trial with a clinician who tracks both your labs and how you actually feel. The goal is the treatment that works for you.