Does this analogy make any sense?
It seems to me upon reading that SHBG acts sort of like a taxicab.
That is: A taxi us used and “pick up” some Testosterone hormone molecules. And then the taxi carries the testosterone throughout the body. And sometimes the taxicab is able to “drop off” the testosterone hormone and it becomes “free”. Then that free T wanders around looking for a motel site that has a vacancy (cell receptor site). And enters into the hotel to do its work.
Other times, the taxicab seems to pick up testosterone hormone and then permanently “locks the doors”, and thus essentially kidnaps the testosterone and binds it up never to let it free.
Some testosterone if free to start with. Those hormones are out walking around free on their own and thus can find their own hotels (cell receptors).
Therefore, the complication of SHBG (taxicab) availability.
First, if in fact the taxicab is necessary for transporting some, if not most of the testosterone to the hotel cell receptor sites with a vacancy, then it is important that there are enough taxi cabs available to provide this important transportation service. This would explain why those with very low SHBG have issues. They don’t have enough taxis to provide enough transportation to get the testosterone to the hotels with vacancies (cell receptor sites.)
Secondly, it is required that these taxicabs have doors that unlock. So, the “fleet mix”, of taxicabs that have doors that open, versus those that don’t is critical. This MIGHT explain why high SHBG, the fleet mix MAY tend to be more heavily weighted towards those taxi’s that the doors remain locked and “binds up” the testosterone. And the remaining free T has a hard time finding a hotel as they must “walk” there rather than be efficiently transported there.
Also, enough free testosterone must be available in order to “hail a cab” and catch a lift. But those hormones don’t know if they will be locked out, or free to get off at a hotel destination, OR be available to walk to the vacant hotel cell site receptors on their own.
Another complicating factor. Is that some of the free testosterone out walking around, has a desire and undergoes gender conversion. That is converts to Estradiol. And this buggers up the whole works, because it too may take up space and use available taxis, but also may check into the cell and create “no vacancy” at the hotel.
Now a proper mix of male (testosterone) and female (Estradiol) components to share a hotel room, or even a hotel makes for some wonderful fun! And this is the optimization point and the “art” of the whole orchestration of this complicated process. Getting the right “mix” of taxi cabs, taxicabs with opening doors, correct number of both male 9testosterong) and female (Estradiol) to be riding and free and checked into sufficient hotels with vacancies.
Seems like “Total T” is able to “count” all the hormone whether free or inside the SHBG taxi cab. Free T only counts those out walking around looking for a vacant hotel, but is unable to count those that are in the SHBG “taxicab”. And SHBG cannot distinguish between which cabs have locked doors, and which taxis have doors that are able to be opened and T dropped off. And there seems to be no way to measure how many hotels have vacancies. And if they have no vacancies, “who” (What hormone) is occupying the room and if they are loitering and unwanted, but won’t leave in order to create a vacancy for the proper (testosterone) tenant to check into the hotel room (Cell).
So does this little analogy make any sense in the broad overview of how all of this may work?