Re: how long does thyroxine stay in the body
Half life of the T4 varies depending on you and your body chemistry.. hypers eliminated it quicker.. than normals.. and hypos retain it the longest.
Pharmacokinetic Parameters of Thyroid Hormones
Hormone ***** Ratio in Thyroglobulin ***** Biologic Potency ***** t1/2 (days)
Levothyroxine (T4) *****10 - 20 ***** 1 ***** 6-7(1)
Liothyronine (T3) ***** 1 ***** 4 ***** ≤ 2
(1) 3 to 4 days in hyperthyroidism, 9 to 10 days in hypothyroidism
What does this mean.. if you are normal it takes 6-7 days after ceasation of hormone treatment to drop to 50% blood concentration after equilibrium was achieved.. then another 6-7 days to reach 25%.. and another week to reach 12.5%.. etc.
In the case of hypers.. the process is halved to 6-7 days off meds drop you to 25% and another week would throw you to 6.25% on average. Hypos retain T4 longer.. most likely as an adaptation of not having enough to begin with.. it takes ~ 10 day cycles for the depreciation of T4 by 50% of the current supplemented T4 levels.
If we learn by our mistakes, I am working on one hell of an education.