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About Hypothyroidism

Key half lives

T3 ~ 2.5 days

T4 ~ 6.5 days

TSH ~ 1 hour

TRH 2.4 and 3.9 min for the initial phase of disappearance and 14.1 and 20.6 min for the later phase of disappearance for TRH and TRH-OH, respectively.

T3 is approximately 4 times as potent as T4 on a ug basis.

Thylor contains a ratio of 4:1 T4:T3 by mass.

Schematic

• Effect of long-term calorie restriction with adequate protein and micronutrients on thyroid hormones
• Could the ketogenic diet induce a shift in thyroid function and support a metabolic advantage in healthy participants? A pilot randomized-controlled-crossover trial
  
• Understanding Local Control of Thyroid Hormones: (Deiodinases Function and Activity)
• Low-T3 Syndrome A Strong Prognostic Predictor of Death in Patients With Heart Disease
• Thyroid Hormone Treatment to Mend a Broken Heart
• Sebastiano Venturi's Iodine history and more
• Differences in hypothalamic type 2 deiodinase ubiquitination explain localized sensitivity to thyroxine

• T3 specifically may reduce Lp(a)
• Low-T3 Syndrome A Strong Prognostic Predictor of Death in Patients With Heart Disease
• Thyrotropin Levels and Risk of Fatal Coronary Heart Disease
• Thyroid Hormone Treatment to Mend a Broken Heart
• Effect of Thyroid Function on LDL Oxidation
• Connection with elevated homocystein and low B12
• Increased insulin levels - IL-6

• New Dimensions in TSH control TSH target looks to be just under 1
• Current Methodology to Assess Bioequivalence of Levothyroxine Sodium Products Is Inadequate This stinks - We need someone besides the government to monitor medicine potency.

• Mechanisms of thyroid hormone action on the insulin-like growth factor system: all thyroid hormone effects are not growth hormone mediated

• Effects of thyroid status on insulin-like growth factor-I, growth hormone and insulin are modified by food intake

as you move from hypothyroid towards hyperthyroid, HDL-C, ApoA-I, and HDL2b/large HDL-P are lowered, and Hepatic Lipase and Cholesterol Esther Transfer Protein are increased. Normally, we think that high HDL-C, ApoA-I, and HDL2b are good -- Perhaps this is where oxLDL comes in - should it be part of the yardstick to set thyroid replacement dosage? And do the declines in HDL cause an increase in oxLDL and Lp(a)?

• Triiodothyronine rapidly lowers plasma lipoprotein (a) in hypothyroid subjects

(These people had no thyroid - not mild hypothyroid).

• Effect of thyroid hormone replacement on lipoprotein(a), lipids, and apolipoproteins in subjects with hypothyroidism.
• Lipoprotein (a) levels and apolipoprotein (a) isoform size in patients with subclinical hypothyroidism: effect of treatment with levothyroxine.
• http://www.sciencedirect.com/science/article/pii/009012299290014F

It looks like the t4/t3 ratio is a key factor - reduces Il-6 which might control Lp(a)?

• Thyroxine replacement dose in patients with Hashimoto disease: A potential role for interleukin-6
• Significant reduction of elevated serum lipoprotein(a) concentrations during levo-thyroxine–replacement therapy in a hypothyroid patient

Desiccated Thyroid - probably a wrong turn

• Could be that people prefer 'Desiccated Thyroid' is that it has both T3 and T4 - and probably somewhat released slowly as it is digested. Can it really be produced in consistent dosages? - probably should not be used.
  • Desiccated Thyroid does not contain human T4 or T3 - it is similar enough to work.
  • It is also claimed that the T3 in Desiccated Thyroid is IR - and will cause a bump in Free-T3 serum levels - this kick may account for (some of?) the preference.
  • Desiccated Thyroid also contain T2 and many other things(perhaps iodine?) - some of which may also be lacking in hypothyroid folks.
  • A very few people do get allergic reactions to Desiccated Thyroid.
  • Desiccated Thyroid can also be given slow release - no studies found.
  • Some people report improvement when switched to Desiccated Thyroid - some the opposite. Most often people are taking T4 mono-therapy - and get T3 if they switch to Desiccated Thyroid which might account for some of the difference. Switching to Desiccated Thyroid from T4+T3 is not likely to result in exactly the same dose or ratio. Quality studies don't exist.

Thyroid factoids

• A missed dose can cause several days of feeling poorly.
• T4 is less well absorbed (48-79%) than T3(95%)
• Thyroid has an effect on most every part of our bodies.

• The discovery that extracts of animal thyroid tissue could cure hypothyroidism was in 1892

• At one time iodine was used to treat hypothyroidism (Why was it stopped when replacement therapy became the norm?)

• There is NO consensus on how to treat hypothyroidism - even among endocrinologists.

• T4 and T3 prescriptions are supposed to be exactly the same thing our bodies make.

• T3 is somewhat unstable at higher temperatures.

• Our thyroid gland makes 20% T3

• The regulation system for thyroid is one of the most precise in nature - keeps T4 and Free-T3 nice and constant.

• Some tissues cannot convert T4 to T3 - most can (the brain has problems here)

• In order to simulate nature - T3 needs to be given slow release - which eliminates any morning 'kick' from the med - no studies exist to see if it might help the wide number of systems it effects.

• Studies comparing T4 vs T4 + T3 have varied results - and are of very poor quality design. The biggest study seems inconclusive (not exactly well designed) . (Little is known of effects on LDL sub-fractions and Lp(a)). They noted that people somewhat preferred T4 + T3 but could not measure why (depression and anxiety scales - cognitive scales etc didn't account for it).

• There is an insane lack of good research on optimizing hypothyroid treatment.

• There are no patents waiting so research funding is unlikely.

• Both to little Thyroid hormone AND too much can result in depression.

• Insulin and T3 interact with each other. Association Between a Novel Variant of the Human Type 2 Deiodinase Gene Thr92Ala and Insulin Resistance

• We don't know the optimal dose of iodine - studies have not been done - no patent possibilities?

• Extremely high and low TSH are indicative of low and high thyroid - it is not clear that intermediate numbers mean that much.

• This study, while interesting - is still a combination of several poor quality studies - not sure what it could possibly mean. Effect of combination therapy with thyroxine (T4) and 3,5,3-triiodothyronine (T3) versus T4 mono-therapy in patients with hypothyroidism, a double blind, randomized cross-over study. Mixing several poor quality soups together will not often result in a great soup.. ..
• Do we need still more trials on T4 and T3 combination therapy in hypothyroidism?

• My hunch is it seems best to take T4 + SRT3 . No studies to back up or refute my hunch. I also think that Free-T3 is the number to tweak - I could be wrong.
  • Update 2015-02-00 Differences in hypothalamic type 2 deiodinase ubiquitination explain localized sensitivity to thyroxine
• Association of Thyroid Function With Life Expectancy With and Without Cardiovascular Disease