Thyroid Hormone Replacement
Thyroid hormone replacement restores hormone levels in hypothyroidism. Levothyroxine (T4) is the standard; alternatives exist for specific situations.
This page covers the options and when each may be considered.
Last medically reviewed: 1 November 2025
Levothyroxine — the standard
Synthetic T4 is the recommended first-line treatment for hypothyroidism — stable, predictable, inexpensive, and well-studied. Most patients do well on it alone.
The body converts T4 to T3 as needed; this physiological conversion usually suffices.
Combination T4/T3 therapy
Some patients report persistent symptoms despite normal TSH on levothyroxine. Trials of adding synthetic T3 (liothyronine) have shown mixed results — guidelines generally do not recommend routine combination therapy.
It may be considered on an individual basis by specialists when symptoms persist despite confirmed adequate T4 replacement and other causes are excluded — never self-prescribed.
Desiccated thyroid extract
Desiccated thyroid (e.g., Armour Thyroid) contains both T4 and T3 from porcine thyroid. It is not recommended as first-line — T3 content causes peak-trough fluctuations, and standardisation varies. Some patients prefer it; switching requires medical supervision.
Its use is controversial and should be discussed with a clinician familiar with thyroid disorders.
Monitoring
Whatever the formulation, TSH monitoring guides dosing. Over-replacement risks atrial fibrillation and bone loss; under-replacement leaves symptoms. Annual (or more frequent) checks ensure optimal control.
Frequently asked questions
Is levothyroxine the only option?
It is the recommended standard, but combination therapy or desiccated thyroid may be considered in specific cases by specialists — not as self-directed alternatives.
Why do I still feel tired on levothyroxine?
Possible reasons: dose not yet optimal, other causes of fatigue, or rarely T3-related issues. A thorough evaluation — not just TSH — determines next steps.
Can I switch formulations?
Only under medical supervision — different formulations have different potencies and switching requires dose adjustment and monitoring.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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