Disclaimer
CompoundIQ publishes research summaries for informational and educational purposes only. Nothing on this site constitutes medical advice, diagnosis, or treatment recommendations. Always consult a licensed healthcare provider. Many compounds listed are research chemicals not approved for human use.
T4 (Levothyroxine)
Also known as: Synthroid, Levothyroxine, Levoxyl, T4
T4 (levothyroxine) is the primary thyroid prohormone produced by the thyroid gland. It is converted to the active T3 by deiodinase enzymes in peripheral tissues. It is the most commonly prescribed thyroid medication and provides a more stable, physiological approach to thyroid supplementation compared to T3.
Risk Level
Medium RiskDifficulty
Intermediate| CAS Number | 51-48-9 |
| Molecular Formula | C15H11I4NO4 |
| Class | Hormone |
| Category | Fat Loss Agents |
Mechanism of Action
T4 serves as a circulating reservoir that is converted to T3 by type 1 and type 2 deiodinase enzymes in liver, kidney, and other tissues. This conversion is regulated by metabolic demand, providing a more stable thyroid hormone level than direct T3 supplementation. T4 has a much longer half-life than T3 (6-7 days vs 1 day), resulting in steadier blood levels.
Dosing Research
Replacement dose: 1.6 mcg/kg/day (typically 75-150 mcg/day). Fat loss protocols may use 100-200 mcg/day. Taken once daily on an empty stomach. Less aggressive effect on metabolic rate than T3 but safer and more predictable. No taper typically needed due to long half-life, but endogenous recovery still applies.
Side Effects & Risks
Generally better tolerated than T3 due to controlled peripheral conversion. Potential side effects include palpitations, anxiety, tremors, insomnia, and heat intolerance at supraphysiological doses. Suppresses endogenous thyroid function. Lower risk of muscle catabolism compared to T3.
Research Studies
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Disclaimer
CompoundIQ publishes research summaries for informational and educational purposes only. Nothing on this site constitutes medical advice, diagnosis, or treatment recommendations. Always consult a licensed healthcare provider. Many compounds listed are research chemicals not approved for human use.