Liothyronine (T3)

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evidence score

fat loss

Prescription Only

T3Cytomeltriiodothyronine+2 more

Liothyronine (T3) is the active form of thyroid hormone, 3-4x more potent than T4 (levothyroxine) and the dominant driver of metabolic rate, thermogenesis, and cellular energy expenditure. In athletes and bodybuilders it is used off-label to increase metabolic rate for enhanced fat loss, particularly during caloric restriction when endogenous T3 levels fall. Medical indications include hypothyroidism, myxedema coma, and thyroid cancer suppression. The risk is significant: exogenous T3 suppresses the hypothalamic-pituitary- thyroid (HPT) axis, requiring a careful taper to restore endogenous production. Requires close medical supervision.

Evidence

No score yet

Safety

Unknown safety profile

Clinical Status

No formal phase listed

Research Sync

Not synced yet

Dosing

Typical

50 mcg

25 mcgRange100 mcg

Frequency2-3x/day (short half-life requires split dosing)

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Pharmacology

Half-life~2.5 days (biological effect days to weeks)

OnsetMetabolic increase within 1-3 days; peak effects 1-2 weeks

DurationHPT axis suppression persists weeks after cessation; requires taper

Routes

oral

Evidence Score

—

0 studies indexed

Scoring Factors

Volume(40%)—

Quality(30%)—

Sample Size(10%)—

Consistency(10%)—

Replication(5%)—

Recency(5%)—

Evidence Levels

AScore ≥75 with at least 1 meta-analysis and 3+ RCTs

BScore ≥50 with at least 1 RCT or meta-analysis

CScore ≥25 — observational or animal evidence only

DScore <25 — very limited or preclinical data

Plain-English Snapshot

Liothyronine (T3) is currently categorized as a fat loss compound.

Evidence scoring has not been fully computed yet, so interpret this profile as preliminary.

Safety scoring is incomplete. Start conservatively and monitor carefully.

Core mechanism

TR-alpha and TR-beta nuclear receptor agonist → increased mitochondrial uncoupling proteins → thermogenesis; upregulates beta-adrenergic receptors; increases Na+/K+-ATPase expression

Practical Context

Strongest current signals

No indexed study summaries yet.

Elevated caution signals

1 severe/high side effect flag