I came across this article on Pub Med which will be of interest to those who are hypothyroid or those of us taking suppliments. In short L Carnitine reduces thyroid function. Who knew?
Effects of carnitine on thyroid hormone
Abstract
By experiments on cells (neurons, hepatocytes, and fibroblasts) that are targets for thyroid hormones and a randomized clinical trial on iatrogenic hyperthyroidism, we validated the concept that L-carnitine is a peripheral antagonist of thyroid hormone action. In particular, L-carnitine inhibits both triiodothyronine (T3) and thyroxine (T4) entry into the cell nuclei. This is relevant because thyroid hormone action is mainly mediated by specific nuclear receptors. In the randomized trial, we showed that 2 and 4 grams per day of oral L-carnitine are capable of reversing hyperthyroid symptoms (and biochemical changes in the hyperthyroid direction) as well as preventing (or minimizing) the appearance of hyperthyroid symptoms (or biochemical changes in the hyperthyroid direction). It is noteworthy that some biochemical parameters (thyrotropin and urine hydroxyproline) were refractory to the L-carnitine inhibition of thyroid hormone action, while osteocalcin changed in the hyperthyroid direction, but with a beneficial end result on bone. A very recent clinical observation proved the usefulness of L-carnitine in the most serious form of hyperthyroidism: thyroid storm. Since hyperthyroidism impoverishes the tissue deposits of carnitine, there is a rationale for using L-carnitine at least in certain clinical settings.
I wouldn't want to avoid L-carnitine, but I wouldn't want to supplement it either (since I'm hypothyroid, not hyperthyroid). It does have positive uses within the body. According to wikipedia :
"In eukaryotic cells, it is required for the transport of fatty acids from the intermembraneous space in the mitochondria, into the mitochondrial matrix during the breakdown of lipids (fats) for the generation of metabolic energy"
Eukaryotic cells are cells with a nucleus, so basically, a huge proportion of the body's cells would be of this type.
Another reason for not eliminating it from the diet :
"In the course of human aging, carnitine concentration in cells diminishes, affecting fatty acid metabolism in various tissues. Particularly adversely affected are bones, which require continuous reconstructive and metabolic functions of osteoblasts for maintenance of bone mass. A 2008 study found that supplementing with L-carnitine decreased bone turnover and increased bone mineral density in rats."
Apparently, vegetarians are likely to get a lot less L-carnitine in their diet than non-vegetarians. I don't have the faintest idea whether this is a good reason for vegetarians to supplement though.
Its interesting as I am supplimenting with it for Fibromyalgia and I am hypothyroid. I am also taking L Tyrosine which helps T4 T3 conversion. I have noticed less aches and soreness in my arthritis as a side effect as well as improved fibro symptoms. I haven't had to increase my NDT nor have I noticed any increase in hypo symptoms so maybe the L tyrosine is counteracting the L Carnitine. Only 3 weeks into this new regime so still early days.
Hi Maggie. I was diagnosed with Hypothyroidism first in my 40's however I now suspect that I was swinging between hypo hyper from my early 20's. The Fibro was diagnosed later but again I suspect that I had it for years. I am also gluten intolerant and the gut plays an important role in Fibro and thyroid problems, so that's no surprise. Not a straight forward answer I am afraid.
L-Carnitine can be used in the treatment of hyperthyroidism as, as Humanbean says, it is used for the transport of fatty acids in the body.
I suppose the advice should be, if you are hypo, don't supplement with L-Caritine, useless you are are having kidney dialysis or taking medication for seizures, then seek advise from your GP re monitoring levels.
I wonder whether acetyl-L-carnitine has the same effect as L-Carnitine...Dr Myhill recommends the former for people with chronic fatigue syndrome..Has anyone experience with using Acetyl-L-Carnitine? Thank you
Thank you Ib003 i've been looking for something natural to help the hyper symptoms that seem to dominate me at the moment, so will research further to see if This is viable for me to try 🐯T
I'm a patient of Dr Myhill, who ran mitochondrial functions tests for me earlier this year. The results were very poor indeed, but one of the problems which was flagged up was a deficiency of acetyl l-carnitine. She recommended I supplement 1g per day of the powder, dissolved in water. I was a near-vegetarian for many, many years and only returned to regular meat-eating about three years ago. Even so, it wasn't enough to get my carnitine levels up within the normal range.
Difficult to say at present, since I have so many health problems, and my mitochondrial function is down to 23%. I've only been following Dr M's treatment programme and Dr Peatfield's revision to my thyroid and adrenal treatments for 2-3 months. It's taken me a long time to get this low, so it will to take a while for any improvements, I think!
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.
L-Carnitine Supplementation may help with mental fatigue in Hypothyroid patients 
Medichecks today only Advanced Thyroid Function Blood Test £86.00 reduced to £74.00 Finger prick
Carnitine, brand name carnitor
What are the best vitamins for Graves Disease is CoQ10 Selenium, and L-Carnitine good supplements? 
