Pharmacokinetics of NDT (DTE)

[diogenes]

I discovered some useful information on NDT pharmacokinetics (rate of uptake, time to achieve peak level in blood, and loss rate). Note that >99% is protein bound, mainly onto thyroglobulin, so it will take time for the hormones to be released from the protein in the stomach/intestine and explains the delay in initial effect and the time it takes to achieve peak level, especially T3. Also we know that T3 taken on its own has a halflife of 1 day, yet it takes 2-.5 days to reach peak level. again indicating slower pharmacokinetics than T3 alone. T4-NDT half-life doesn't seem to differ from T4 alone. The different bioavailability also suggests slower uptake of NDT.

Mechanism of Action

Natural thyroid hormone from animals; increase basal metabolic rate, increase utilization and mobilization of glycogen store, promotes gluconeogenesis

Pharmacokinetics

Onset: Initial effect: 3hr

Bioavailability: 48-80%

Protein Bound: >99%

Metabolism: Hepatic; also in kidney and intestinal walls

Metabolites: Levothyroxine (T4), liothyronine (T3), reverse triiodothyronine (rT3)

Excretion: Urine (major), feces (partially)

Time to peak

T4: 2-4 hr

T3: 2-3 days

Half-Life

T4: 6-7 days (euthyroid); 3-4 days (hyperthyroid); 9-10 (hypothyroid)

T3: 2.5 days

[TaraJR]

linda96

[Hidden]

Amazing, thanks diogenes, this is why I can take NDT with levo, it seems more gentle, when I took levo and t3 synthetic it was dreadful for me..this slow action seems to suit me

[amala57 in reply to Hidden]

I'm exactly the same. Doing well on T4 & NDT but on synthetic t3 & T4 could not sleep, had palpitations & felt very unwell. I wish my gp & endo understood this.

[Hidden in reply to amala57]

Yeah, had palpitations nonstop on synthetics, insomnia etc. Still not yet where I should be, but at least now I know what suits me. Synthetics t3 for me was too stimulating.

[amala57 in reply to Hidden]

Me too. Will never take synthetic t3 again. NDT plus a little t4 is good for me.

[FancyPants54 in reply to Hidden]

I think I'm the same. T3 with Levo did nothing good for me at all. NDT, although still working up my dose, feels so much more stable.

[tattybogle]

All these people saying how difficult it is to manufacture a slow release form of T3 and how someone needs to develop one before they can possibly recommend it's 'user friendly' inclusion in thyroid hormone replacement therapy.... etc etc ..... and it turns out they've already got one .....right under their piggy little noses.

Doh !

[TSH110]

Fascinating. I have most certainly got my life back since taking NDT. If only they would reinstate it and prescribe in on NHS . Why does something so simple seem like an impossible dream?

[jimh111]

Thanks. I assume this is from the medscape document?

It would be useful if the manufacturers published the study and in particular reveal the dose the subjects TFTs before and after so that we have some idea what it relates to. I assume the Time to Peak and Half Life of T3 are based on a bolus dose of NDT that has its T4 converted to T3 over time. As you mentioned the T3 half life is one day.

It would be really useful to know the actual phamacokinetics of NDT, it could be argued that for any endocrinologist who is interested in delivering T3 and T4 in the correct ratio combination therapy with levothyroxine and NDT is the obvious solution. The patient with primary hypothyroidism gets better treatment and the endocrinologist gets humble pie.

[LindaC]

Thank you, yet again, diogenes - I did rather well on this via Dr S, then NHS but, when foolish enough to accept 'their [flawed] for me' ranges + labs wouldn't test - I used more T3 (as Dr P advised in any event) but always enjoyed Armour. 💚

[tattybogle]

just adding link to the source of this info: reference.medscape.com/drug...

your later post discussing this :

healthunlocked.com/thyroidu... rerun-medscape-and-dte-ndt

and this one discussing testing times: healthunlocked.com/thyroidu... suggested-thyroid-hormone-test-timing-protocols