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Month: May 2016

Tyranny of the TSH

Tyranny of the TSH

The Tyranny of the TSH

Let’s talk about further thyroid testing.  In an effort to reduce laboratory costs and find ever cheaper methods of evaluating thyroid function, the TSH has become the more commonly accepted first line test with “reflex” follow-up.

Now this assumes three very important concepts.

  1. The feedback mechanism between the pituitary and the thyroid is intact and functional.
  2. It assumes a “normal distribution.” That is, a typical “bell shaped” curve of all values from low to high.
  3. That we can assign “reasonable” upper and lower cut-off values.

Idealized Thyroid Feedback

Refer to figure 1.  You can see that TSH is part of a functional feedback loop.   High values infer hypothyroidism (under-active thyroid) and low values infer hyperthyroidism (over active thyroid).   The TSH values are opposite (inverse) to thyroid activity.  A compensatory mechanism.

thyroid schema
fig 1

But there is human variation.  It is an idealized loop that is not as precise as an integrated circuit.  A result of overly simplified mechanistic thinking.  There are rare situations where hypothalamic dysfunction can cause very low TSH levels rather than feedback from low thyroid activity.  This is termed central hypothyroidism.

We have steadfastly maintained over the last 15 years that complete thyroid analysis should include a TSH, free T4 and a free T3.  Frequently adding the reverse T3 and thyroid antibodies.  Refer to our previous post.   The TSH is a poor measure of free T3 — the active metabolite or driver of metabolic function.

What is a Normal Distribution?

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Aging Research Topics and Meetings

Aging Research Topics and Meetings

Aging and Age-Related Conferences and Updates:

Fotolia-meeting2

[We are indebted to John Furber for these timely and comprehensive updates on aging and anti-aging research, meetings and conferences]

(updated 9 April 2016)

 

Disease Drivers of Aging: 

2016 Advances in  Geroscience Summit

April 13-14, 2016, New York City

Co-sponsored by AFAR, GSA, NIH, NYAS

www.nyas.org/Geroscience2016

 

Cognitive Aging Conference

April 14-17, 2016, Atlanta, Georgia, USA

http://cac.gatech.edu/

 

31st International Conference

Alzheimer’s Disease International

April 21-24, 2016, Budapest, Hungary

http://www.adi2016.org/

 

Biomedical Innovation for Healthy Longevity

April 25-28, 2016, St. Petersburg, Russia

http://www.ivaoconf.org/

 

There’s much more …

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