Here are some links to the reasons why you need to have these levels of certain vitamins and minerals checked and their connection to your thyroid and metabolic status.

Low iron/ferritin:
http://www.thewayup.com/newsletters/081504.htm and http://www.ithyroid.com/iron.htm.
I also used the following article in our last TPA Newsletter
http://www.femail.com.au/iron-levels-tony-pearce.htm

Low vitamin B12:
http://www.ncbi.nlm.nih.gov/pubmed/18655403

Low vitamin D3:
http://www.eje-online.org/cgi/content/abstract/113/3/329 and
http://www.goodhormonehealth.com/VitaminD.pdf

Low magnesium:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC292768/pdf/jcinvest00264-0105.pdf

Low folate:
http://www.clinchem.org/cgi/content/full/47/9/1738 and
http://www.liebertonline.com/doi/abs/10.1089/thy.1999.9.1163

Low copper/zinc:
http://www.istanbul.edu.tr/ffdbiyo/current4/07 Iham AM?R.pdf
http://articles.webraydian.com/article1648Role_of_Zinc_and_Copper_in_Effective_Thyroid_Function.html

It is essential that you have a correct level of Selenium and Zinc as both are needed for conversion of the mainly INACTIVE thyroid hormone thyroxine into the ACTIVE form of the thyroid hormone T3.