L-carnitine supplementation for the management of fatigue in patients with hypothyroidism on levothyroxine treatment: a randomized, double-blind, placebo-controlled trial– Endocrine Journal – 2016 – free full-text
Hypothyroid patients experience fatigue-related symptoms despite adequate thyroid hormone replacement.
Thyroid hormone plays an essential role in carnitine-dependent fatty acid import and oxidation.
We investigated the effects of L-carnitine supplementation on fatigue in patients with hypothyroidism.
In total, 60 patients (age 50.0 ± 9.2 years, 3 males, 57 females) who still experienced fatigue (fatigue severity scale [FSS] score ≥ 36) were given L-carnitine (n = 30, 990 mg L-carnitine twice daily) or placebo (n = 30) for 12 weeks.
After 12 weeks, although neither the FSS score nor the physical fatigue score (PFS) changed significantly, the mental fatigue score (MFS) was significantly decreased by treatment with L-carnitine compared with placebo (from 4.5 ± 1.9 to 3.9 ± 1.5 vs. from 4.2 ± 1.8 to 4.6 ± 1.6, respectively; P < 0.01)
In the L-carnitine group, 75.0%, 53.6%, and 50.0% of patients showed improvement in the FSS score, PFS, and MFS, respectively, but only 20.0%, 24.0%, and 24.0%, respectively, did so in the placebo group (all P < 0.05).
Both the PFS and MFS were significantly improved in patients younger than 50 years and those with free T3 ≥ 4.0 pg/mL by treatment with L-carnitine compared with placebo.
Additionally, the MFS was significantly improved in patients taking thyroid hormone after thyroid cancer surgery.
These results suggest that L-carnitine supplementation may be useful in alleviating fatigue symptoms in hypothyroid patients, especially in those younger than 50 years and those who have hypothyroidism after thyroidectomy for thyroid cancer (ClinicalTrials.gov: NCT01769157).
And here’s what WebMD has to say:
The following doses have been studied in scientific research:
- For L-carnitine deficiencies in adults: 990 mg two to three times per day in tablets or as an oral solution.
- For preventing side effects caused by valproic acid (Depacon, Depakene, Depakote, VPA): 50 to 100 mg/kg/day in three or four divided doses, to a maximum of 3 grams/day.
- For chest pain and congestive heart failure (CHF): 1 gram twice daily.
- Following heart attack: 2 to 6 grams daily.
- For symptoms of overactive thyroid: 1-2 grams twice daily.
- For male infertility: 2 grams of L-carnitine plus 1 gram of L-acetyl-carnitine daily.
L-carnitine is LIKELY SAFE for most people when taken by mouth and when used as an injection, with the approval of a healthcare provider. It can cause side effects such as nausea, vomiting, stomach upset, heartburn, diarrhea, and seizures. It can also cause the urine, breath, and sweat to have a “fishy” odor.
Special Precautions & Warnings:
- Pregnancy and breast-feeding: There is not enough reliable information about the safety of using L-carnitine if you are pregnant. Stay on the safe side and avoid use.
- Taking L-carnitine is POSSIBLY SAFEin breast-feeding women when taken by mouth in the amounts recommended. Small amounts of L-carnitine have been given to infants in breast milk and formula with no reported side effects. The effects of large amounts taken by a breast-feeding mother are unknown.
- Children: L-carnitine is POSSIBLY SAFE when used appropriately by mouth or intravenously (by IV), short-term.
- Under-active thyroid (hypothyroidism): Taking L-carnitine might make symptoms of hypothyroidism worse.
- Kidney failure: Using DL-carnitine has been reported to cause symptoms such as muscle weakness and eye drooping when administered intravenously (by IV) after dialysis. L-carnitine does not seem have this effect.
- Seizures: L-carnitine seems to make seizures more likely in people who have had seizures before. If you have had a seizure, do not use L-carnitine.
L-carnitine is an amino acid (a building block for proteins) that is naturally produced in the body.
L-carnitine supplements are used to increase L-carnitine levels in people whose natural level of L-carnitine is too low because they have a genetic disorder, are taking certain drugs (valproic acid for seizures), or because they are undergoing a medical procedure (hemodialysis for kidney disease) that uses up the body’s L-carnitine.
It is also used as a replacement supplement in strict vegetarians, dieters, and low-weight or premature infants.
- heart-related chest pain,
- congestive heart failure (CHF),
- heart complications of a disease called diphtheria,
- heart attack,
- leg pain caused by circulation problems (intermittent claudication), and
- high cholesterol.
Some people use L-carnitine for
- muscle disorders associated with certain AIDS medications,
- difficulty fathering a child (male infertility),
- a brain development disorder called Rett syndrome,
- chronic fatigue syndrome,
- overactive thyroid,
- attention deficit-hyperactivity disorder (ADHD),
- leg ulcers,
- Lyme disease, and
- to improve athletic performance and endurance.
The body can convert L-carnitine to other amino acids called acetyl-L-carnitine and propionyl-L-carnitine. But, no one knows whether the benefits of carnitines are interchangeable. Until more is known, don’t substitute one form of carnitine for another.
How does it work?
L-carnitine helps the body produce energy. It is important for heart and brain function, muscle movement, and many other body processes.