Question: I had a total thyroidectomy (in 2007 and due to papilloma cancer) and all was perfect until my pill was changed in January 2013. My weight shot up 35lbs in 3 months, I am very tired, I have joint aches and my hair is thinning. I think my T3 is lower than it should be but my Endo will not put me on Natural Desiccated Thyroid (NDT) - which has T3 as well as T4, because she says that if you are over 65 it could cause a stroke. I am 72 - but a very young 72. Is this true? I can energetically seek out a new doctor who will give me NDT, but will not if there is any risk of a stroke (there is nothing wrong with my heart, btw).
I have never been a sickly person in my life, just this cancer due (I think) to radiation exposure on the job.

Dear Dr XXXXXXX
Thank you so much for replying to my question, and forgive my delay but I couldn't get to my computer until now.
Something I tried to add in my initial question but didn't do it right was, the following:
I too was struck by the full column of "normals" on my test results and couldn't understand it since I am very obviously hypOthyridic. I did actually calculate some ratios which I am led to believe have significance.
My TT4 to TT3 ratio is 74:1 (unless I have made a mistake in the math!) and it is supposed to be 17:1,
My FT3 to rT3 is 15 and it is supposed to be >20
My TT3 to rT3 is 5 while it is supposed to be >10.
It is for these reasons I think I have a conversion (T4 to T3) problem.
Upon reading your reference I am even more determined to fix what I perceive as a T3 conversion problem, do you think that these ratio anomalies are significant?
One final favor, and I hope I am not asking too much. Could you please work out my T4 to T3 ratio and tell me what you get. A 74:1 is absurd but would be a clincher to get transferred to NDT - I do like my Endo and do not want to upset her but I feel she is dead wrong on this one. If I can present her with concrete evidence then I do not feel so bad in requesting a change of doctor.
Thank you so much for your attention, XXXX

Hello again and thank you very much for your help. Actually I am now very intrigued with something: The TT4 to TT3 ratio. Your answer is much closer to what one might expect but you used TT4 in mcg/dL to TT3 in ng/dL, and you also did TT3/TT4 is that the convention? I simplistically thought one might have to reduce both to the same units to get a ratio. Do you have a reliable reference where I could read about this? I have tried Googling it but my results were sketchy and what I thought was the right one (i.e. get 'em to the same units) gave me 74:1 - which doesn't sound anything like the 17:1 which is quoted everywhere.

Thank you SO much, you have completely answered my questions. I hope my ignorance and lack of education in the medical sciences didn't drive you crazy. I did find a reference which spelled all of this out precisely and you are dead right, one measures in ng/dL for TT3 and mcg/dL for TT4 then you get the conventional ratios. I come from a physics background and we have to convert to the same units before we call it a ratio hence my confusion and wrong answer. Oh, and it's TT3/TT4 my bad - I also got it the wrong way up.
OK all is very clear now, I REALLY appreciate your patience and your explanations, it is really important to me that I understand things. XXXX

P.S. Here is that ref.
HORMONES 2004, 3(2):120-126
DOI:
Research paper
The serum triiodothyronine to thyroxine (T3/T4) ratio in various thyroid disorders and after Levothyroxine replacement therapy
A. Mortoglou, H. Candiloros
Department of Endocrinology, Diabetes and Metabolism, XXXXXXX Medical Centre Hospital, XXXXXXX Greece.
http://www.hormones.gr/91/article/article.html