question from a user
Should trt be given when total testosterone is normal but free testosterone is low? can this legitimately cause symptoms? Also If shbg is not the cause and free testosterone is still low what could be hogging it up?
AlphaMD's Answer
Good question. The short answer is yes. Normal total testosterone with a low free T will cause symptoms. In fact, the ONLY test needed to diagnose hypogonadism is a low free T.
There are a few definitions that are important to know:
Total testosterone - this is the total amount of testosterone in your body, that includes testosterone which is bound to sex-hormone binding globulin (SHBG), T which is bound to albumin, and free T.
Bioavailable testosterone - This is the amount of free testosterone and testosterone attached to albumin. Essentially, this is the amount of T your body can use.
Free testosterone - This is the amount of T that your body can use RIGHT NOW.
Sex hormone binding globulin - On average, ~44% of total testosterone is bound to SHBG. However, SHBG can vary widely, and go up or down based on many factors. Any T bound to SHBG is PERMANENTLY bound and is effectively inert from then on.
Albumin - ~55% of total testosterone is WEAKLY bound to albumin. Albumin levels are fairly stable in the average person who has no kidney or liver disease.
T is not available for use while attached to albumin, but albumin releases it fairly easily when needed.
So, now that you have those definitions, we will go through a few scenarios. First, should TRT be given when total T is normal, but free T is low. This scenario occurs when the body has a high amount of SHBG, effectively eating up most of the testosterone. While you can try to lower SHBG through lifestyle changes, typically this takes a lot of time to make it low enough to counteract the symptoms of low T.
Ways to lower your SHBG include cutting out alcohol, cutting out carbs, cutting out caffeine, losing weight, increase your protein intake. The only supplement that has actual scientific evidence to lower SHBG is magnesium. All others (vitamin D, fish oil, etc) do not have enough evidence to prove that they work.
In the situation where your Total T is normal, and your Free T is low, but your SHBG is also low, then that means that your albumin level must be high. Again, albumin elevation is common in liver and kidney disease. Insulin raises albumin, so if you are in the pre-diabetic stage where your body is trying to produce more, or if you use insulin as a medication, that will raise albumin.
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