Tuesday, September 18, 2012

Avoiding Dissicated Thyroid Hormone Replacement is still a good idea .

Avoiding Dissicated Thyroid Hormone Replacement is still a good idea . Please see my November discussion and comments below from people who felt that there is benefit in taking  a little T3 . I still agree with the FDA that desiccated thyroid is obsolete.  There is a FDA approved product with reliable content of T4 and T3, Thyrolar .

 #1 Question ?
                    What is  the structural difference between T4 and T3 ?
     Answer -
                     One iodine molecule ( T4 has 4 iodine molecules and T3 has 3 )

#2 Question True/ false
                     T3 is the  active metabolic form of thyroid hormone.

     Answer -  True,
                      T4 is the inactive primary form of thyroid hormone produced in the thyroid gland. The
                      T4 is then slowly converted to T3 by enzymes in our tissues by removing 1 iodine
#3  Question ?
                     Why not cut out the  "middle man , T4 " and just take the active form of the hormone T3 ?

       Answer ? The short answer is that it is just not safe for every one.  T3 is almost 100%  absorbed
                        and produces an elevated T3 level with every dose. This can produce extra demands on
                        a persons heart.
                       T4 is a longer lasting hormone that slowly converts to the metabolically active , T3 ,
                        delivering a steady stable supply of T3 to our tissues. There is a small percent of
                        people who genetically are unable to convert T4 to T3  , and will benefit from taking a
                        medication containing T4 and T3 such as Thyrolar .

#4 Question?
                    Is there any reason for ever using pure T3 ?
     Answer -
                     Yes. I used Cytomel ( T3 )  , because of its short half life , as part of the process in
                      evaluation of patients with thyroid cancer.

 There is some evidence that some people may need to take a little bit of T3 to get the full benefit from thyroid replacement. I have attached an abstract of an article supporting the idea below.

J Clin Endocrinol Metab. 2009 May;94(5):1623-9. Epub 2009 Feb 3.
Common variation in the DIO2 gene predicts baseline psychological well-being and response to combination thyroxine plus triiodothyronine therapy in hypothyroid patients.
Panicker V, Saravanan P, Vaidya B, Evans J, Hattersley AT, Frayling TM, Dayan CM.
Henry Wellcome Laboratories for Integrative Neurosciences and Endocrinology, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, United Kingdom.
Animal studies suggest that up to 80% of intracellular T(3) in the brain is derived from circulating T(4) by local deiodination. We hypothesized that in patients on T(4) common variants in the deiodinase genes might influence baseline psychological well-being and any improvement on combined T(4)/T(3) without necessarily affecting serum thyroid hormone levels.
We analyzed common variants in the three deiodinase genes vs. baseline psychological morbidity and response to T(4)/T(3) in 552 subjects on T(4) from the Weston Area T(4) T(3) Study (WATTS). Primary outcome was improvement in psychological well-being assessed by the General Health Questionnaire 12 (GHQ-12).
The rarer CC genotype of the rs225014 polymorphism in the deiodinase 2 gene (DIO2) was present in 16% of the study population and was associated with worse baseline GHQ scores in patients on T(4) (CC vs. TT genotype: 14.1 vs. 12.8, P = 0.03). In addition, this genotype showed greater improvement on T(4)/T(3) therapy compared with T(4) only by 2.3 GHQ points at 3 months and 1.4 at 12 months (P = 0.03 for repeated measures ANOVA). This polymorphism had no impact on circulating thyroid hormone levels.
Our results require replication but suggest that commonly inherited variation in the DIO2 gene is associated both with impaired baseline psychological well-being on T(4) and enhanced response to combination T(4)/T(3) therapy, but did not affect serum thyroid hormone levels.


Avoid Desiccated Thyroid Hormone Replacement

Avoid Desiccated Thyroid Hormone Replacement

Desiccated thyroid hormone , Armour thyroid and Thyroid USP is listed as obsolete by the FDA but continues to be prescribed and used by some people . I recently saw a video promoting the use of desiccated thyroid which prompted me to write this note.

Our thyroid gland produces thyroid hormone in a response to TSH ( thyroid stimulating hormone ) from our pituitary gland. The primary form of thyroid hormone produced and released into our blood is T4 . This T4 is slowly converted to the active hormone T3 in our tissues,primarily the liver . The T3 Hormone in correct amounts helps keep all of the cells of our body running at peak efficiency.

A deficiency of T4 and T3 results in a slow down of all of the machinery in our body and an excess of T4 and T3 can have toxic effects especially for our heart causing arrhythmia , heart failure , angina or even cardiac arrest. The effect of excess T3 is a concern for anyone with heart disease.
( many of us have a little silent coronary heart disease ).

So, why is desiccated thyroid hormone not a recommended treatment for hypothyroidism ?

Desiccated Thyroid Hormone is of animal thyroid tissue origin. This means that it contains a mixture of T4 and T3. The T3 is almost 100% absorbed rapidly producing abnormally high levels of T3 in the blood stream and potentially a toxic effect on that persons heart.

Levothyroxine ( L-thyroxine , levothyroid , synthyroid and others) is T4 and is much safer to use. The T4 is absorbed and converted slowly to the active T3 , similar to the function of a normal thyroid gland. Be safe . If you need thyroid hormone replacement, use T4.
Dr. Calder


  1. Hey very interesting blog!
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  2. This doctor or whatever he is...doesn't know what he's talking about. Most who suffer from hypothyroidism have found that T4 only treatment is horrible and that we DO NOT convert T4 to T3 readily. It has also been proven that taking NDT (Natural Desiccated Thyroid) helps prevent heart problems and heart attacks. Do the research Dr. Calder. I tried T4 only treatment and still felt like crap. Adding T3 into my regime only made things worse. It wasn't until I started taking NDT that I got optimized and all my hypo symptoms went away. Try looking up Janie Alexander Bowthorpe's STTM page on Facebook. 7000 of us strong and 90% of those on this board take NDT and have found it far superior to T4 only treatment. You are just like the 5 or 6 Endo's that I have fired who told me..."here take this one little pill (T4) and it will make you feel all better. To that I say BS! T4 does nothing but make most people sicker. Adding in T3 helps...but it is NDT that really makes the difference
  3. Thanks for your comment. We are fortunate to have a variety of options available to help manage the various medical problems we all deal with in our lives. It is good that you found something that works for you. Dr. Calder
  4. Hi, it seems to be very complex. I think a lot of people who are hypothyroid, most of whom have autoimmune disease, do not respond well to T4 alone. I appreciate you bringing up concern about risks, but going untreated or unsuccessfully treating with T4 is also risking heart problems. Not to mention many untreated or T4-supplemented patients whose lives have come to a standstill because of extreme fatigue, memory problems, and mood swings. So treating immune and adrenal imbalance and its possible causes with diet and safe herbs and supplements, and if necessary proceeding cautiously with whatever form of thyroid hormone works to improve life in general, seems imperative.

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Your comments and questions are appreciated. David Calder,MD