T Nation

Video: T Assay Precision and Accuracy, Evolution of Reference Ranges

Invested some time to make this video about T assay accuracy and precision and the evolution of the T reference ranges.

Its a bit long but I also wanted to include some basic principles of analytical chemistry to allow the viewer a better understanding of this topic

@enackers Thanks for motivating me to make this video.

Final version now online.

For those not interested in understanding the background and the implications just watch the video from 23:57 - 32:50 to get the most important message.


It says the video has been removed?

Just uploaded the final version.

Awesome, watching it now

Interesting new paper about a potential decline in T levels in young US men

This is a good example of what I am referring to. Keeping in mind the systematic bias between assays as discussed in the video, the interpretation of the data is questionable.

They used an IA assay between 1999 and 2004 (no decline within 5 years), in 2011 and 2012 they used a GC-MS based assay (sharp decrease within 6 to 7 years and between 2013 and 2016 they used another LC-MS based assay (no decline, actually a slight increase can be observed).
So a single sharp decrease exactly at the point in time where they changed the assay.

Very good video. I hope it at least convinces some people to be more open minded regarding the “decline” that is often referenced based on the change in reference ranges.

Very few people know enough to intelligently go against the current thinking that you showed in one of the early slides, so it’s good to see you doing this since you’re obviously very educated and experienced in this field and are able to do so.

Now, will you go on dbossa’s channel? :running_man:

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Thanks. Happy that you liked it.

No. But everyone is free to share :slight_smile:

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Did you see this new study. I’ll watch the video.


CONCLUSIONS: There was a highly significant age-independent decline in total testosterone in the first and second decades of the twenty-first century. The decline was unlikely to be explained by increasing rates of obesity.

I am not saying that I know for 100% that there is no decline in T levels after adjustment for BMI, disease, smoking etc.
I am saying that the literature is controversial on that topic and that one has to really carefully evaluate the databasis when interpreting the studies.’

'In two of the previous observational reports [2, 4] adjustment to body mass index (BMI) led to a nullification of the period-related changes in testosterone. However, in the other two observational reports [1, 3] the age-specific testosterone decline remained significant after adjustment to BMI.

Regarding BMI:
‘In this analysis we did not adjust for BMI, as this is unclear whether BMI is a potential mediator or confounder since BMI has not been established as a sole explaining parameter in previous studies on longitudinal trends of testosterone. Analysis performed on the research population with available data on BMI showed little variation (< 1 kg/m2) in the mean age-specific BMI between study periods, with no discernible trend (data not shown). We therefore suggest that the observed testosterone decline is not likely to be explained by obesity trends.’

Thats interesting because Israel is experiencing almost the same increase in obesity rates as the US. In 2018 25% of the 15 year old males were obese. 50% of young men were overweight. In 2000 these numbers were 18% obese and 35% overweight.

It definitly needs to get thoroughly investigated because if this is true, whatever the cause may be, its scary.

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