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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
T3 is approximately 4 times as potent as T4 on a ug basis.
Thylor contains a ratio of 4:1 T4:T3 by mass.
- 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)?
(These people had no thyroid - not mild hypothyroid).
It looks like the t4/t3 ratio is a key factor - reduces Il-6 which might control Lp(a)?
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
- 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.
- 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.
- 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.