Mr. Kite,
Before reading your response I researched L-Carnitine to bits. My research led me to research it in relation to thyroid disease, both Grave's disease and Hashimoto's.
WoW....
L-Carnitine is an antagonist of thyroid hormone...Mr. Kite, you are right.
Here's the link by the NIH...
http://www.ncbi.nlm.nih.gov/pubmed/11502782?dopt=Abstract
Sallysblooms...Why do I pulse my supplements. I'll add a link, but just google multi-vitamin and breast cancer. Huge number of links...Here's one
http://www.medicalnewstoday.com/articles/183880.php
The lesson is to research supplements before taking them.
After researching L-Carnitine, I wish I could take it. If I could, I would certainly be taking a brand that uses
Carnipute...A Swiss made brand.
All the best...