@climateguy As always, my thanks for your continued insightful and helpful contributions here, but let me start by apologizing for the sheer length of what follows. It's a bit verbose, and above and beyond what the average forum member cares to know, but hopefully, it will be of some help to those interested in this topic of tE2-ADT.

Now, as you might expect, given my own demonstrated interest in the subject, I am familiar with the Estradiol Initiative website and much of the information provided there, and in-fact, I had previously viewed the specific chart that you've referenced here. However, I must say, I had not looked at it nearly as closely as I should have, because on second glance, it certainly does answer several key questions.

On its face, at least for me personally, the core subject of converting patch concentrations of tE2, to gel concentrations, would seem to be rather simple and straight-forward. By example, if the Patch/Stampede trial guidelines called for four (4) patches (marketed as delivering 0.1 mg of tE2), applied roughly twice weekly, then by extension, it would appear that a comparable gel application, would simply be 0.4 mg of total tE2, in a small volume of gel (lets say 0.4 mg/mL), with 1.0 mL volume of gel being applied, also twice weekly.

The problem is, I'm told by numerous sources including manufacturers and pharmacists, that for some unknown reason, the absorption dynamics differ from a patch to a gel, purportedly by a factor of 10x (i.e., tE2 in patches being absorbed 10x more efficiently than from gel). Unfortunately, none of these folks have been willing to stand by this estimated formulation factor, nor have any been able to provide documentation to support such a conversion factor. Perhaps more importantly, that 10x figure appears to differ exponentially from what is seen with commercially available gels, which are often (by example), 0.1% (i.e., 1.0 mg tE2 delivered per single mL of a gel packet weighing 1.0g). Needless to say, whatever the true or most accurate conversion factor may actually be, I remain reluctant to proceed with any special order gel formulation, until I can achieve more reliable clarification on the matter.

Lastly, regarding the graph of Serum E2 levels vs. Patch Strength and/or Gel Volume that you referenced here - while its helpful in several meaningful ways, this graph is also problematic on several levels: . . .

First and foremost, it lists 'by name' five (5) different brands of estradiol gels, many (if not most) of which, are available in different (variable) concentrations, which were not specifically identified as being used in the studies depicted on this graph. In other words, only the total volume of gel used was specified, NOT its concentration of tE2 (was it 0.025%, 0.01%, 0.06%, 0.1%, etc.?), making it essentially impossible to extrapolate to the patches used, which were specifically cited as delivering in units of ug/24 hours.

Secondly, of the total twenty-six (26) triangular and round multi-colored data points illustrated in the graph (red, blue, yellow, lime, dark green, etc.), all but three are for 'gels' of unspecified concentration, but more importantly, all 26 were data points from post-menopausal women (not male prostate patients). And while the results for the only three (3) remaining data points (which are in-fact associated with males), appear to be linear, they were from 'patch' use (not gel), and they were at relatively insignificant serum E2 levels, well above the 100 pg/mL range of testosterone, needed to achieve castration (<50 ng/dL).

Anyway, this next and final point doesn't help resolve the potential long-term availability issue often associated with patches, but if all else fails, there are commercial tE2 gel products readily available out there, that contain both practical volumes of gel (1.0 mL), and at suitably appropriate ('deliverable') levels of tE2 (0.1-1.0 mg), to effectively mirror the daily Patch/Stampede application protocol, depending upon the volume applied.