T4 (Levothyroxine / Synthroid)
3,5,3',5'-Tetraiodothyronine. Thyroid Hormone, metabolic hormone.
This page describes what T4 (Levothyroxine / Synthroid) is and its known risks. It is not medical advice and not a guide to using it. Many of these substances are prescription-only or illegal to use without a prescription. Speak to a doctor.
- Class
- Thyroid Hormone
- Legal status
- Prescription only
- Half-life
- 7 days
- Liver strain
- Low
- Kidney strain
- Low
- Converts to estrogen
- None
- Suppresses natural hormones
- Not typically
Medical uses
- Hypothyroidism
- Thyroid cancer
- Goiter
What it does in the body
Metabolic
- Increased metabolic rate (milder than T3)
- Fat loss (slower than T3)
- Converts to T3 in body
Forms, half-life and detection
| Form | Half-life | Reported detection window |
|---|---|---|
| Oral | 7 days | Not tested |
Side effects and health risks
Hormones and fertility
- Thyroid suppression
Heart and blood vessels
- Increased heart rate (milder than T3)
- Palpitations
Musculoskeletal
- Muscle loss (less than T3)
Neurological
- Anxiety
- Insomnia
Related compounds
Questions
What is the half-life of T4 (Levothyroxine / Synthroid)?
About 7 days. Half-life is the time for the level in the blood to fall by half.
How long is T4 (Levothyroxine / Synthroid) detectable?
Testing windows of Not tested are reported, depending on the test and the person.
Is T4 (Levothyroxine / Synthroid) legal?
Prescription only. Laws differ by country and change; check the rules where you live.
What blood tests matter with T4 (Levothyroxine / Synthroid)?
Ask a doctor which tests suit you.
What are the side effects of T4 (Levothyroxine / Synthroid)?
Hormones and fertility: thyroid suppression. Heart and blood vessels: increased heart rate (milder than t3) and palpitations. Musculoskeletal: muscle loss (less than t3).
For information only, not medical advice. MyoStats is a tracking tool used at your own discretion. Speak to a doctor before changing your training, diet, medication or anything you take.