Defining the lag of TSH response to thyroxine

[diogenes]

This paper though enormously mathematically difficult, makes a very important point. That is, the relationship between FT4 and TSH is affected by a slow TSH reaction to T4 dose. It is available to download.

Published online 2022 Aug 8. doi: 10.15252/msb.202210919 

Dynamics of thyroid diseases and thyroid‐axis gland masses

Yael Korem Kohanim, 1 Tomer Milo, 1 Moriya Raz, 1 Omer Karin, 1 Alon Bar, 1 Avi Mayo, 1 Netta Mendelson Cohen, 2 Yoel Toledano, 3 and Uri Alon 1

 Abstract

Thyroid disorders are common and often require lifelong hormone replacement. Treating thyroid disorders involves a fascinating and troublesome delay, in which it takes many weeks for serum thyroid‐stimulating hormone (TSH) concentration to normalize after thyroid hormones return to normal. This delay challenges attempts to stabilize thyroid hormones in millions of patients. Despite its importance, the physiological mechanism for the delay is unclear. Here, we present data on hormone delays from Israeli medical records spanning 46 million life‐years and develop a mathematical model for dynamic compensation in the thyroid axis, which explains the delays. The delays are due to a feedback mechanism in which peripheral thyroid hormones and TSH control the growth of the thyroid and pituitary glands; enlarged or atrophied glands take many weeks to recover upon treatment due to the slow turnover of the tissues. The model explains why thyroid disorders such as Hashimoto's thyroiditis and Graves' disease have both subclinical and clinical states and explains the complex inverse relation between TSH and thyroid hormones. The present model may guide approaches to dynamically adjust the treatment of thyroid disorders

[DippyDame]

Definitely above my head!!

embopress.org/doi/full/10.1...

[nellie237 in reply to DippyDame]

Above mine too...........and most if not all Endo's/GP's heads too, I expect DD

[diogenes Remembering]

Expanding on the paper's conclusions. The main one is that if on therapy which depresses TSH (however caused) the TSH-producing part of the pituitary atrophies (shrivels). Thus if a rise into the "normal range" of TSH is desired, it cannot be done without a long delay. The longer the suppression of TSH, the harder it is to do if indeed it can be done at all. Conversely, if there has been elevated TSH for a while, the gland swells to encourage the thyroid to make as much hormone (T4 and T3) as it can. On treatment to resolve the TSH level, there is a delay of weeks or longer for the gland to reduce in size and action. When patients are being treated by a doctor, they should point out that TSH response is considerably delayed on treatment. And those who have had no TSH for years can explain that the pituitary is unlikely to recover on any reduction of dose. This is another very nice addition to our group's arguments which are fully quoted.

[Musicmonkey]

Awesome! Thank you.