The cornerstone of hypothyroidism treatment — T4, T3, and NDT: how each works, clinical dosing, monitoring, and how to find a provider who actually tests Free T3.
Levothyroxine (T4) and liothyronine (T3) are the two active thyroid hormones used in hormone replacement. T4 is the long-lasting storage form; the body converts it to active T3 as needed. Natural desiccated thyroid (NDT) — Armour Thyroid, NP Thyroid — provides both, plus T2 and T1, from porcine thyroid glands.
All are prescription-only, FDA approved for hypothyroidism. Standard of care is T4-only replacement (Synthroid, levothyroxine). Patients who feel poorly on T4 alone may do better with combination T4+T3 or NDT — which typically requires finding a provider comfortable prescribing beyond the basic protocol.
FDA approved. Prescription only. Not WADA prohibited at replacement doses, but elevated exogenous thyroid use flagged in some sport contexts.
Levothyroxine (T4) is biologically inactive until deiodinated to T3 in peripheral tissues. Long half-life (~7 days) makes once-daily dosing feasible and stable.
Liothyronine (T3) is the biologically active hormone that binds nuclear thyroid receptors. Short half-life (~1 day) means dose fluctuations are felt more sharply. Some patients have impaired T4→T3 conversion (DIO2 polymorphisms) and do better with direct T3.
Desiccated porcine thyroid contains T4, T3, T2, T1 in a fixed ratio (~80:20 T4:T3). Natural ratio differs from human thyroid; some patients feel better on it, others don’t. Works well when baseline T4-only treatment leaves lingering symptoms.
| Benefit | Evidence |
|---|---|
| Hypothyroid symptom resolution | Gold-standard replacement; typically normalizes within 6–12 weeks of proper dosing |
| Energy & metabolism | Restored BMR and energy in hypothyroid patients |
| Cognitive function | Brain fog resolves with euthyroid restoration |
| Weight management | Resolves weight gain caused by hypothyroidism; not effective as a weight-loss drug in euthyroid patients |
| T4+T3 combo vs T4 alone | Mixed trials; ~10–20% of patients feel substantially better on combination therapy |
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeTSH alone is insufficient. A proper panel includes:
Long-term over-replacement (suppressed TSH) increases risk of atrial fibrillation and bone density loss. "Optimizing" thyroid by running labs above range is not a free win.
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Thyroid Hormones (T3 / T4) is a prescription medication. StackTrax does not sell, prescribe, or facilitate purchase of prescription drugs.
Find a clinician who can order baseline lab work, screen for contraindications, monitor your response, and adjust dosing over time. Options to consider:
Before starting, you’ll typically want:
Avoid sources that offer prescription medications without labs, medical history, or licensed-provider oversight. If a telehealth service promises a prescription after a 5-minute questionnaire, that’s a red flag.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeDisclaimer: This guide is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. The compounds discussed are not FDA approved for human use. Always consult a qualified healthcare provider before starting any new supplement or peptide protocol. StackTrax does not sell peptides or supplements directly — purchase links go to third-party vendors. StackTrax is not responsible for the products, quality, or business practices of any third-party vendor. This page contains affiliate links — StackTrax may earn a commission on purchases at no extra cost to you.
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