Well, the salt may help her feel better, but it might not warm her up. My understanding is that Synthroid stresses the adrenals. With her low bp, she looks to have adrenal fatigue. It's also possible that additionally she has low serum sodium and/or low serum potassium. It's common to have those two electrolytes out of balance when adrenals are struggling. She could also have low iron, even without appearing anemic on blood tests. If her doctor can't help, the Yahoo NTHAdrenals group can help. They'll ask her to get a saliva cortisol test, iron blood testing, CMP (complete metabolic panel) that includes potassium and sodium, and B12 test, then help her with understanding where to go from there.