Research that supports Measuring Free T3 and the efficacy of Supressed TSH levels

[handsinclay]

I am a Hashi's patient for many years but only recently became enlightened as to the importance of monitoring  Free T3 levels to reach my optimal health.  In addition, My docs have over the years reduced my thyroid meds based on TSH levels until I reached a crisis point this past summer.  Never again, I have promised myself!

I am sharing this info from the medical literature for those who may want to read/share.

Below you will find some previously posted references (thank you) and some other references from the National Institutes of Health database (pubmed) that support Free T3 testing and find the beneficence of suppressed TSH levels.

Please add any other helpful suggestions/evidence to this thread.

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http://www.ncbi.nlm.nih.gov/pubmed/9284722?dopt=Abstract
J Clin Endocrinol Metab. 1997 Sep;82(9):2931-6.
Low thyrotropin levels are not associated with bone loss in older women: a prospective study.

"We found no consistent evidence that low TSH, a sensitive biochemical marker of excess thyroid hormone, was associated with low BMD (Bone Mineral Density) or accelerated bone loss in older ambulatory women."
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http://www.ncbi.nlm.nih.gov/pubmed/16322336?dopt=Abstract
Endocr Relat Cancer. 2005 Dec;12(4):973-81.
Lack of deleterious effect on bone mineral density of long-term thyroxine suppressive therapy for differentiated thyroid carcinoma.

"In conclusion, long-term suppressive LT4 treatment does not appear to affect skeletal integrity in women with differentiated thyroid carcinoma."

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http://www.ncbi.nlm.nih.gov/pubmed/1366242

Ir J Med Sci. 1992 Dec;161(12):684-6.
TSH as an index of L-thyroxine replacement and suppression therapy.
"It is theoretically possible that patients receiving exogenous L-thyroxine for primary hypothyroidism should have suppressed TSH levels if physiological needs are constantly met. "

"TSH was suppressed in 23 patients (51.1%), normal in 20 (44.4%) and elevated in 2 (4.5%). When TSH was suppressed, FT4 was elevated in 30.4% but normal in 69.6% of patients."

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http://www.ncbi.nlm.nih.gov/pubmed/26335522

Endocr Connect. 2015 Dec;4(4):196-205. doi: 10.1530/EC-150056.
Variation in the biochemical response to l-thyroxine therapy and relationship with peripheral thyroid hormone conversion efficiency.

"These findings imply that thyroid hormone conversion efficiency is an important modulator of the biochemical response to l-T4; FT3 measurement may be an additional treatment target; and l-T4 dose escalation may have limited success to raise FT3 appropriately in some cases."

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http://www.ncbi.nlm.nih.gov/pubmed/25623348

Zhonghua Xin Xue Guan Bing Za Zhi. 2014 Dec;42(12):1017-21.
[Relationship of serum free T3 with the coronary artery calcification and major adverse cardiac events in patients with suspected coronary artery disease].


"FT3 levels are associated with coronary artery calcification scores and the incidence rate of MACE (Major Adverse Cardiac Events) in patients with suspected coronary artery disease. A low FT3 level is considered as an important risk factor of high calcification scores and MACE (Major Adverse Cardiac Events)."

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http://www.ncbi.nlm.nih.gov/pubmed/25404437

J Coll Physicians Surg Pak. 2014 Nov;24(11):806-9. doi: 11.2014/JCPSP.806809.
Reference intervals for free T3 and free T4 in Pakistani euthyroid patients: effect of age and gender on thyroid function.

"There was no effect of gender and age on FT3 and FT4. The age with serum FT3 and FT4 significantly negatively correlated but this correlation was stronger for FT3 as compared to FT4 levels. Reference intervals of FT3 and FT4 for male (2.99 - 5.63 pmol/L, 12.3 - 22.6 pmol/L) and female (2.77 - 5.29 pmol/L, 11.7 - 22.1 pmol/L) respectively are suggested."

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http://www.ncbi.nlm.nih.gov/pubmed/25364675

Indian J Endocrinol Metab. 2014 Nov;18(6):811-4. doi: 10.4103/2230-8210.141355.
Cognitive function in subclinical hypothyroidism in elderly.

"Prevalence of cognitive impairment was significantly higher in subclinical hypothyroidism as compared to controls. Presence of cognitive impairment correlated with the level of TSH; as TSH increased cognitive function declined."

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http://www.ncbi.nlm.nih.gov/pubmed/24708095

J Clin Endocrinol Metab. 2014 Jul;99(7):2467-76. doi: 10.1210/jc.2013-3832. Epub 2014 Apr 7.
Thyroid hormones and mortality risk in euthyroid individuals: the Kangbuk Samsung health study.

"In a large cohort of euthyroid men and women, FT4 and FT3 levels within the normal range were inversely associated with the risk of all-cause mortality and cancer mortality, particularly liver cancer mortality."

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[gimel]

If you want to get into specific scientific studies, I think you will find a lot of useful info included in the extensive list of references with this link, which is being presented for consideration in the writing of the NICE guidelines.

http://www.thyroiduk.org/tuk/TUK_PDFs/The%20Diagnosis%20and%20Treatment%20of%20Hypothyroidism%20%20August%202017%20%20Update.pdf

[handsinclay]

Here's another research paper involving pediatric clients:

TITLE:  The ratio of serum free triiodothyronine to free thyroxine in children: a retrospective database survey of healthy short individuals and patients with severe thyroid hypoplasia or central hypothyroidism.

http://www.thyroidresearchjournal.com/content/8/1/10
Thyroid Research 2015, 8:10  doi:10.1186/s13044-015-0023-5

"In the Control group, the FT3/FT4 ratio was 3.03 ± 0.38 10 −2  pg/ng (mean ± standard deviation) with no age or gender differences. A/Hypoplasia patients showed a significantly decreased mean FT3/FT4 ratio (2.17 ± 0.33, P < 0.001) compared to Control patients, with decreased FT3 and elevated FT4 levels. The Central group also showed a significantly decreased FT3/FT4 ratio (2.55 ± 0.45, P < 0.001) compared to the Control group, with decreased FT3 and equivalent FT4 levels."

"Conclusions :  The FT3/FT4 ratio appears to be constant between the ages of 3–17 y. Children on L-T4 due to congenital thyroid a/hypoplasia or central hypothyroidism have a decreased FT3/FT4 ratio compared to short normal children."

[fikennard]

Many thanks for this post .. I am trying to collate evidence for Improve Thyroid Treatment Group ITT who are stake holders in the writing of the NICE guidelines... all info needed by Nov 13th 2017

[fikennard]

Many thanks for this post .. I am trying to collate evidence for Improve Thyroid Treatment Group ITT who are stake holders in the writing of the NICE guidelines... all info needed by Nov 13th 2017

[Red_Star]

"As a homeostatically integrated parameter, TSH becomes neither normatively fixed nor a precise marker of euthyroidism. This is exemplified by the therapeutic situation with l-thyroxine (l-T4) where TSH levels defined for optimum health may not apply equivalently during treatment. In particular, an FT3-FT4 dissociation, discernible FT3-TSH disjoint, and conversion inefficiency have been recognized in l-T4-treated athyreotic patients."

"As a consequence, the use of TSH, valuable though it is in many situations, should be scaled back to a supporting role that is more representative of its conditional interplay with peripheral thyroid hormones.
This reopens the debate on the measurement of free thyroid hormones and encourages the identification of suitable biomarkers. Homeostatic principles conjoin all thyroid parameters into an adaptive context, demanding a more flexible interpretation in the accurate diagnosis and treatment of thyroid dysfunction."

Homeostatic Control of the Thyroid-Pituitary Axis: Perspectives for Diagnosis and Treatment. Front Endocrinol (Lausanne). 2015 Nov 20;6:177. doi: 10.3389/fendo.2015.00177. eCollection 2015.

PMID: 26635726 [PubMed] PMCID: PMC4653296

[handsinclay]

Thanks Red Star.  
This all helps us advocate for ourselves.  My doctor is going to be getting a lot of reading to do!

[gimel]

Thanks for posting the info.  There was a couple I hadn't previously seen.  You can never have enough ammunition when trying to change doctors'  long-held, and incorrect beliefs, about suppressed TSH.  

[handsinclay]

Amen!  

Gimel, I have appreciated  all your references and links as they have helped me learn so much.  You and others on the panel of "Top Thyroid Answerers" have helped me make significantly better health decisions. Hooray for this panel!

Now I hope and pray that the science will SOON catch up with what thyroid patients already know, namely to be in optimal health Free T3 often needs to be in upper third of the range and Free T4 somewhere in the middle of the range.