The two stickies here have tons of info, plus this one:
http://forum.lowcarber.org/showthread.php?t=449748

200-260 TC is lowest all cause mortality, esp for women.

I had 253 TC last year, and some minor symptoms of low thyroid. I started taking iodine, a few other MDA suggestions, http://www.marksdailyapple.com/why-.../#axzz1yvXLrxcT
and one month later both TC and LDL were lower, but I still won't worry about those numbers.

If you dont want any non-essential X-Rays to your chest, the carotid artery ultrasound is a second best.