Minireview: The Neural Regulation of the Hypothalamic-Pituitary-Thyroid Axis

There are many reasons to question the conventional approach to thyroid levels which insists on the central and absolute position of TSH.

Thankfully, at least some medical/scientific folk do have an inkling of this and we can sometimes see deeper thoughts.

I have always wondered why the thryoid has a considerable innervation. What on earth does it need those nerves for? Surely it doesn't actually require any more nerves than other parts of our bodies, our endocrine systems? Or does it?

Endocrinology. 2012 Sep; 153(9): 4128–4135.

Published online 2012 Jul 3. doi: 10.1210/en.2012-1467

Minireview: The Neural Regulation of the Hypothalamic-Pituitary-Thyroid Axis

Ricardo H. Costa-e-Sousa and Anthony N. Hollenberg

Abstract

Thyroid hormone (TH) signaling plays an important role in development and adult life. Many organisms may have evolved under selective pressure of exogenous TH, suggesting that thyroid hormone signaling is phylogenetically older than the systems that regulate their synthesis. Therefore, the negative feedback system by TH itself was probably the first mechanism of regulation of circulating TH levels. In humans and other vertebrates, it is well known that TH negatively regulates its own production through central actions that modulate the hypothalamic-pituitary-thyroid (HPT) axis. Indeed, primary hypothyroidism leads to the up-regulation of the genes encoding many key players in the HPT axis, such as TRH, type 2 deiodinase (dio2), pyroglutamyl peptidase II (PPII), TRH receptor 1 (TRHR1), and the TSH α- and β-subunits. However, in many physiological circumstances, the activity of the HPT axis is not always a function of circulating TH concentrations. Indeed, circadian changes in the HPT axis activity are not a consequence of oscillation in circulating TH levels. Similarly, during reduced food availability, several components of the HPT axis are down-regulated even in the presence of lower circulating TH levels, suggesting the presence of a regulatory pathway hierarchically higher than the feedback system. This minireview discusses the neural regulation of the HPT axis, focusing on both TH-dependent and -independent pathways and their potential integration.

Full paper freely available here:

ncbi.nlm.nih.gov/pmc/articl...

4 Replies

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  • Thanks Rod, interesting article, Dr. Hollenberg again. PR

  • I wonder if the medics read this stuff and think, "Hmm. Quite a complicated little gland, this thyroid. Still, sod the patients, just bung 'em Levo."?

  • I suspect that in most cases you could have stopped at the word "and". :-)

    Mind, a GP simply cannot spend sufficient time keeping up with everything. The system we have where the GP is gatekeeper for almost everything requires that they do keep up, which is one reason the system as a whole fails.

  • Lol - and absolutely right. But you'd expect the sodding endos to keep up, no?

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