Health Research (thyroid hormone focus)

study on membrane fluidity of thyroid gland in rats with iodine deficiency or iodine excess][Article in Chinese]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?itool=abstractplus&db=pubmed&cmd=Retrieve&dopt=abstractplus&list_uids=11372391
Yan Y, Fang H, Xiang J.
Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China.

OBJECTIVES: To explore the effect of iodine deficiency and excess on thyroid membrane fluidity and its pathogenesis.

METHODS: Wistar rats were fed different levels of iodine in the diet (normal iodine as control, low iodine and excess iodine).
Serum T4 and T3 levels, thyroid superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and malondialdehyde (MDA) content were determined, and two parameters of polarization (Pr) and micro-viscosity (eta) using DPH as a florescence probe were tested.

RESULTS: Serum T4 and T3 levels in the low iodine (LI) group were markedly decreased, and the thyroid SOD and GPx activities and MDA content were significantly increased compared with the other two groups.
However no changes were found in the high iodine (HI) group. There were no differences in Pr and eta values among three groups at 12th week of experiment, but at 24th week, both Pr and eta values in LI group were increased significantly compared to the other two groups. But the effect of iodine excess as expected was not found in this study.

CONCLUSIONS: Long-term iodine deficiency caused a marked increase of membrane micro-viscosity and decrease of membrane fluidity in rat thyroid gland. Oxidative damage of thyroid by free radicals and retardation of lipid metabolism are considered as two important pathogenesis factors.

PMID: 11372391 [PubMed - indexed for MEDLINE]
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 However these 2 studies did find problems with excess iodine compared o optimal(normal) amounts

Effect of chronic mild and moderate iodine excess on thyroid anti-oxidative ability of iodine deficiency and non-iodine deficiency Wistar rats] [Zhonghua Yi Xue Za Zhi. 2006] PMID: 16796889

[Effects of supplementation of different kinds of iodine on the antioxidative ability of retina in iodine deficient rats] [Zhonghua Yan Ke Za Zhi. 2003

Well I've heard this before from research scientists who have done tissue sampling when studying thyroid hormones, but now I've finally found a study
http://endo.endojournals.org/cgi/reprint/137/6/2490.pdf

Note_ p 2495 , or p 6 of 13 in pdf
"We have shown that using T4 or T3 alone" ( and yes it was time released! as they used continuous infusion via  pumps.. comment added for proponents of time release T3 ONLY )
" it is not possible to met either one of the two possibilities simultaneously for plasma and tissues (1,5) despite the wide ranges of doses used in the studies..."
"when infusing T4 alone, supraphysiological T4 concentrations have to be reached in most tissues to normalise their T3 concentrations, and this occurs at different T4 concentrations for different tissues(1).

When using T3 alone, T4 concentrations in plasma and tissues are always very low, and supraphysiological T3 concentrations have to be reached in the circulation to normalise T3 levels in many tissues(5) "

My personal feelings/symptoms/blood test results  and my observations from reading of many others experiences on a thyroid forum would fit in with the above. They including
blood test results and dosages on various thyroid hormones from T4 alone, to T3 alone (usually time released), and including many "combos"  and doses both using synthetic T4 and T3 and using a pig's thyroid based thyroid hormone replacement both alone or with added T4 /T3.

NOTE: The ratios  in above study are correct for a rat NOT a human, but the general principle of euthyroidism (normality) in all tissues on a physiological ratio of T4 and T3 still holds for humans in my opinion...

Unfortunately we'll have to stick with rats at present; as obtaining tissues from humans is rather difficult!(perhaps those who undergo stomach stapling or removal of various parts.  Even if patients did volunteer their tissues after removal by independant surgical procedures, it is almost impossible to form a study from the subjects/patients and test the effects of various thyroid hormones.  As well as the logisitic difficulties,and only being able to test removed tissues, which would usually be only one tissue type per patient!,  the patients would have to undergo surgical thyroid removal  weeks before their other surgery! followed by thyroid hormone replacemnent at varying levels set as determined by the study. Thyroid removal for the sake of a study is clearly not acceptable!!. )
Hence the rats( this comment for those who dismiss studies as irrelevant as they were on rats and not humans!)

slightly off topic
I recall it mentioned at uni that liver is way higher in T4 than the thyroid gland.. like eat liver to get T4 if desperate?..and this backs it up?
I still remember this and plan to go for lamb's fry in the case of a shortage of thyroid hormones if desperate; perhaps I could freeze dry it? I still wonder if it would work?

comments welcome