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What is Free T

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Posted 2/17/2014 10:28 AM (GMT -5)
As I mentioned in another post, my new uro ordered a test called the free T. I don't understand what that means. My T level is 664 and the free T is 10. The nurse expressed it as 10%, but I'm not sure that's correct. I just don't know what it means, especially in reference to the T levels.

Can anyone explain it?
Posted 2/17/2014 10:50 AM (GMT -5)
The number you got could be a percentage or an absolute number. Testosterone in the bloodstream can be bound to albumin or bound to SHBG (sex hormone binding globulin) or free - not bound to anything at all. Free T is the amount that your body can easily use, and it's typically a measurement of truly free T and albumin bound T.

If your absolute free T level is 10, that would definitely be low. But, if it was 10% of the 664, or 66, it would be an acceptable level, although at the lower end of an age-graded reference range.

Overall, the 664 seems to be a decent number. When I started taking testosterone, well before my PCA diagnosis, my total T was under 200 and my free T was around 20. My endocrinologist wanted my total T to get up to the 800-1000 range. He doesn't even test my free T levels.
Posted 2/17/2014 8:10 PM (GMT -5)
Thank you. I still do not understand the relevance of the free t, but I would probably need a better understanding of organic chemistry.

But thanks again for the explanation. It does help.
Posted 2/17/2014 8:39 PM (GMT -5)
Think of free T as the stuff that does good things for you. T that is bound to SHBG isn't easily used by the body. So, someone with a very high total T but whose body overproduces SHBG will have a potentially low free T, and may display symptoms of hypogonadism.

My doc tested both up front, found that the percentage of total T that was free (unbound) was reasonable, so he had no reason to suspect SHBG problems. So, to save money, he now only tests total T.
Posted 2/18/2014 9:05 AM (GMT -5)
I no longer have the source document to give credit but here are the notes I took:

"PSA Free%<10 suggest prostate cancer 8 times more likely
PSA Free 10-25% suggests BPH is 3 times more common than prostate cancer
PSA Free% > 25 rarely associated with cancer"

I think there is some minimum threshold for these percentages to make sense.

I my case the testosterone with Lupron on the job is <003 and the freeT% is <1.6% making my free T <<0.048.

For some unexplained reason, I have no fatugue, so will take it.

So not much T there whether it be clinging or circulating free.

LupronJim
Posted 2/18/2014 9:35 PM (GMT -5)
Dmlvt, thank you. That helps a lot. It sounds like my total t and free t is in range. I appreciate your efforts to help me out.

LupronJim, as I recall, a free psa less than 15% is suspicious for PCa. Greater than 25% suggests that there is not PCa. Between those numbers is the twighlight zone....mine was 18%...lol

Sounds like the Lupron is doing the job it was designed to do. I also did not suffer fatigue while on ht. My biggest SE was the hot flashes, and zero libido which has not really returned to what it was before. Now, having said that....a lot has changed in that time period, so the reduced libido might not be the fault of ht.

Thank you for your thoughts...
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