Hair mineral analysis is much more accurate because it shows what is actually absorbed into your tissues and cells which include the hair. You can have high levels of anything in your blood but low absorption so it does not get into the cells/tissue which is where it has the real effect.
In general when massive changes happen to a person all of a sudden my first guess would be parasites.
Our bodies go into 3 8-hour phases in a 24 hr period. During the time 4am until noon your body is detoxifying so when your eat cooked food the detoxification comes to a hault because your body has to work to create enzymes. If you eat raw food until noon (fruits, veggies like carrots,cucumber,tomatoes,romaine or any others) you are not getting away of your body detoxing. This won't fix the problem but it would help slow it down.

"Also, he used to take Iodine supplement last year. Did not help a bit. Nothing changed."

Sorry, but doctors are notoriously ineffective at confirming Iodine deficiency. They are blinded by their ineffective testing. You give the doctors & their tests too much credit. Low body temp is thyroid problems.... period. There can be no other explanation.

How much Iodine did he take (in mg) daily? What kind of iodine, how long and did he take the required co-supplements? Did he also take selenium? Iodine without selenium is ineffective, and can cause problems to get worse.
https://docs.google.com/document/d/1IzFKo-r2-Nn8_z0KUrOhHdlanzSuhkuV3QO03XF6YTY/edit#

I highly recommend reading this outstanding site:
Why do Doctors FAIL to identify Hypothyroid ?
===========================================
I have been involved with iodine & resulting deficiency diseases for years, and this is a very common complaint that I see. Here is what I have found:
They typically deny that iodine & selenium is required for our thyroid. They typically prefer to prescribe synthetic thyroid hormones. IMO, they want lifetime customers dependent on drugs. Curing the thyroid with cheap iodine & selenium is bad for business.
They depend on a USELESS blood test called TSH. “Dr. Derry discovered exactly what we, as patients, have experienced for more than three decades! Namely, not only has the TSH lab failed to reveal that we were ALREADY hypothyroid, it fails us when we are dosing our medication. In other words, the TSH is thoroughly unrelated to how we feel! This has been ESPECIALLY true when using inadequate T4-only meds, and it continues to be true when we start on (preferred) desiccated thyroid if we are forced to stay within the TSH range.” Complete details on why TSH is so useless: http://www.stopthethyroidmadness.com/tsh-why-its-useless/
“Stop the Thyroid Madness” explains why so very many doctors are simply incompetent. http://www.stopthethyroidmadness.com/doctors-need-to-rethink/ A variety of actual, real-life statements, both humorous and pitiful, made by doctors and reported by their patients are pitiful examples. http://www.stopthethyroidmadness.com/give-me-a-break/
STTM Explains how to find a good doctor: http://www.stopthethyroidmadness.com/how-to-find-a-good-doc/

There is only one test to verify iodine deficiency: The urine analysis test:
http://www.hakalalabs.com/testing.html
At least prove to yourself that he is, indeed severely iodine deficient by ordering this test. Be sure to also order the companion bromide & fluoride testing. Bromide & fluoride toxins overwhelm the iodine receptors to make people VERY sickly, so that iodine cannot even be absorbed.

Grizz