Winters lays out some of his thinking here:
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and here:
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To your point, he needs to weave the concept of free E2 and free T into his analysis and discussion. As you point out, too often TT and fT are used interchangeably and their relationship via SHBG isn't fully fleshed out (leaving the interested reader in the dark).
Regarding your question in bold above:
My thinking (for untreated man) is higher levels of SHBG should promote weaker negative feedback at H/P (via the reduced concentration of free T and E2 via aromatase mediated conversion of said fT) per unit of endogenously produced fT. free E2 (primary) and fT (secondary) being what drive negative feedback of gonadotropins. Hence the plot he should also show is SHBG vs accurately measured fT levels (LC-MS/MS + ED).
Thought experiment is to make a step change in SHBG for untreated man and then see response on serum fT.
I am not familiar with any data that shows SHBG directly regulates LH secretion. Hence, we are left with the second part of the argument. If I was the PI my first reaction is to recreate the companion plots this time with SHBG vs accurate fT. Wish we could talk this over at a conference table. Difficult via forum.
