I dont know about all the details in that quote, but the fundimental issue of thyroid is properly diagnosing the problem. The TSH level tha most doctors consider normal is between 5 and .5 where the LOWER the number the more active your thyroid is. the problem is that this is a very broad range, plus if you look at the statistics behindd it the mean and average values are below 2.
this is important, you or your SO know your health beter than your doctor. Find a doctor that will treat the symptoms not the lab results. Go to an endocrinologist, and dont be afraid to tell him/her that you 'dont feel right' even if they tell you you look normal.
The effect on my W was dramatic in overall health, not just libedo. The part that I still dont understand (ok Im a guy, HD, and a ludite) is the feeling that if 'she really loved me she would make an effort... right?' and the resentment / frustration that this brought. She has told me that before being on the thyroid pills, she just didn't have the feeling of wanting. THe problem wasn't in her head, it was in her body.