What is my Peak TT based on known trough level?

[DaveK22]

I inject Test Cyp E3.5D subq, on Mon eve and Fri am. I typically do my blood work on Mon am which is 12 hr from the true trough.

My recent blood work had 747 TT. So is there a "best guess" as to what my peak TT would be based on knowing TT 12 hrs from the trough? And how much would TT typically drop in 12 hrs?

 

[Joey786]

Hard to say. Your shbg levels will play a role though. lower shbg higher peaks. If your shbg is high there might not be that big of a difference between peak and trough.

 

[Cataceous]

I inject Test Cyp E3.5D subq, on Mon eve and Fri am. I typically do my blood work on Mon am which is 12 hr from the true trough.

My recent blood work had 747 TT. So is there a "best guess" as to what my peak TT would be based on knowing TT 12 hrs from the trough? And how much would TT typically drop in 12 hrs?

Without having your particular dose-response relationship there's enough guesswork to make the accuracy of the prediction pretty questionable. But here it is: Assume a serum T peak at one day post-injection, followed by an exponential decay of 2 days, and a T cypionate half-life of 5 days. So Peak * exp(-ln(2)/5*2) = 747 ng/dL. This puts the peak at 986 ng/dL.

 

[Cataceous]

Hard to say. Your shbg levels will play a role though. lower shbg higher peaks. If your shbg is high there might not be that big of a difference between peak and trough.

This is not correct. The apparent half-lives of testosterone esters are essentially not affected by SHBG. The half-lives are governed by the slow rate of absorption of the injected depots.

 

[DragonBits]

Without having your particular dose-response relationship there's enough guesswork to make the accuracy of the prediction pretty questionable. But here it is: Assume a serum T peak at one day post-injection, followed by an exponential decay of 2 days, and a T cypionate half-life of 5 days. So Peak * exp(-ln(2)/5*2) = 747 ng/dL. This puts the peak at 986 ng/dL.

There are many references to the half life of T cypionate to be 8 days, why do you pick 5 days?

 

[Cataceous]

There are many references to the half life of T cypionate to be 8 days, why do you pick 5 days?

I also used to think it was longer, but then @madman called me on it, and after researching it further I had to concede the point. The references supporting the 5-day figure are much stronger, and 90+% of the anecdotal results in the forums also points to 5 days.

 

[Vince Carter]

So is there a "best guess" as to what my peak TT would be based on knowing TT 12 hrs from the trough? And how much would TT typically drop in 12 hrs?

This can't be answered there's no part of this that is linear like that. The best course of action is to start doing your routine like most other people do, you choose to be different in that regard; Mon AM, Thurs PM, blood draw Mon AM before shot.

 

[DragonBits]

Without having your particular dose-response relationship there's enough guesswork to make the accuracy of the prediction pretty questionable. But here it is: Assume a serum T peak at one day post-injection, followed by an exponential decay of 2 days, and a T cypionate half-life of 5 days. So Peak * exp(-ln(2)/5*2) = 747 ng/dL. This puts the peak at 986 ng/dL.

Half life of testosterone esters are affected by the carrier oil, it could that is what is causing the difference 7 vs 5 days half life.

So let me see if I understand this.

Peak*exp(-ln(2)/half life*(time to peak-days after injection).

How many days to you think it takes Nebido to peak after an injection?

I took 3 tests after a Nebido injection, the half life of testosterone undecanoate in castor oil is reported to be 33.9 days. (Half life of testosterone undecanoate in tea seed oil is 20.9 days.)

BTW:
I took 3 total T tests after Nebido,

Post injection = total T.
20 days = 1492
51 days = 584
71 days = 541

Using your formula, it seems like the decay near the end should be greater but it's more flat line and I would have expected.

 

[Cataceous]

Half life of testosterone esters are affected by the carrier oil, it could that is what is causing the difference 7 vs 5 days half life.
...

As I recall, madman pointed out that there are flaws in the studies coming up with the longer half-life. When corrected they also point to ~5 days as the half-life. I would stick with this figure.

...
Peak*exp(-ln(2)/half life*(time to peak-days after injection).
....

The equation uses time after peak, not time before, with the peak occurring right at zero time:

T(time_after_peak) = Peak * exp(-ln(2) / half_life * time_after_peak)

The model just assumes a pure exponential decay after the peak serum level is reached.

...
...
How many days to you think it takes Nebido to peak after an injection?
...

I'd been thinking it's longer, but it seems to be around a week.

...
...
I took 3 tests after a Nebido injection, the half life of testosterone undecanoate in castor oil is reported to be 33.9 days. (Half life of testosterone undecanoate in tea seed oil is 20.9 days.)

BTW:
I took 3 total T tests after Nebido,

Post injection = total T.
20 days = 1492
51 days = 584
71 days = 541

Using your formula, it seems like the decay near the end should be greater but it's more flat line and I would have expected.

Your first two measurements give a reasonable half-life of 23 days. The final measurement is indeed much higher than if there were a continued exponential decay. This just shows the shortcomings of the model and/or a measurement anomaly.

If we assume a one-week post-injection delay to peak then we can work backwards using your 23-day half-life to find that your peak testosterone is estimated to be 2,200 ng/dL.

 

[Cataceous]

...
20 days = 1492
51 days = 584
71 days = 541

Using your formula, it seems like the decay near the end should be greater but it's more flat line and I would have expected.

Alternatively, you could toss the middle measurement, in which case the half-life is calculated as 35 days, and the predicted peak is 1,930 ng/dL.

 

[DragonBits]

Alternatively, you could toss the middle measurement, in which case the half-life is calculated as 35 days, and the predicted peak is 1,930 ng/dL.

I have more measurements, but they are "corrupted" because either I had mixed in HCG or after 56 days I did a combo treatment of adding 1-2 click testosterone cream using DMSO with 1 click or dmso 1 click, 1 click no dmso, nightly, which boosted my total T to 932 even after 88 days.

The only other "clean" measurement I have is after 16 days of the first nebido injection, my total T was 1389, (when I tested after 20 days = 1492) suggested that the peak was 16+ days, who knows what the + might be.

Right now it's been 19 days since my last injection, I have ordered a total T / E2 test, when do you suggest I test? (I am thinking about 25 days.)

BTW, I am doing tests right now because me PSA levels had jumped up and down, up and down, I am leaning towards it being some sort of prostatitis, though I have no symptoms. I wanted to see if the high levels of T/E2 had any affect.

 

[DragonBits]

As I recall, madman pointed out that there are flaws in the studies coming up with the longer half-life. When corrected they also point to ~5 days as the half-life. I would stick with this figure.


The equation uses time after peak, not time before, with the peak occurring right at zero time:

T(time_after_peak) = Peak * exp(-ln(2) / half_life * time_after_peak)

The model just assumes a pure exponential decay after the peak serum level is reached.



I'd been thinking it's longer, but it seems to be around a week.



Your first two measurements give a reasonable half-life of 23 days. The final measurement is indeed much higher than if there were a continued exponential decay. This just shows the shortcomings of the model and/or a measurement anomaly.

If we assume a one-week post-injection delay to peak then we can work backwards using your 23-day half-life to find that your peak testosterone is estimated to be 2,200 ng/dL.

Maybe body size explains some of why I have a higher total T than indicated by the chart, at ~140 lbs, I am smaller than the average, blood volume at least is dependent on body size. Therefor total T is less diluted in a smaller person.

 

[Cataceous]

...
The only other "clean" measurement I have is after 16 days of the first nebido injection, my total T was 1389, (when I tested after 20 days = 1492) suggested that the peak was 16+ days, who knows what the + might be.

Right now it's been 19 days since my last injection, I have ordered a total T / E2 test, when do you suggest I test? (I am thinking about 25 days.)
...

So 16 days after your first Nebido injection you measured 1,389 ng/dL, and the time you measured 1,492 was 20 days after a subsequent injection? If so the latter is expected to be higher because the Nebido was still accumulating.

If it were me I would want to test at the same number of days post-injection every time. This would help tell if you've stabilized.

 

[DragonBits]

So 16 days after your first Nebido injection you measured 1,389 ng/dL, and the time you measured 1,492 was 20 days after a subsequent injection? If so the latter is expected to be higher because the Nebido was still accumulating.

If it were me I would want to test at the same number of days post-injection every time. This would help tell if you've stabilized.

Good point about accumulating. It did make me look at the old data more intensely.

The measurement at 1389 was actually after the second injection in 2018 (I thought it was the first, but I neglected to code it correctly in my spreadsheet), the one at 1492 was the 8th injection. At 18 months I should be as stable as it gets.

So if all this info hangs together, anything post 20 days should be lower and likely my levels were higher at say 10 days after an injection. But my aim isn't to determine the exponential roll off of serum levels, nor when I peak nor how high, though all of that is interesting. BTW, 31 days before this first injection, my "base" level with no exogenous hormones was 348 ng/dl. Interesting is that in June 1996, my base level was 376, so it really hasn't changed over those years. Too back I never got tested when I was much younger.

(FWIW, I actually started Nebido first in 2009, but took a three year break ending 5/2018 when I went back on Nebido. I didn't do a lot of testing the first 5 years of nebido.)

thanks, it did all help me understand this.

 

[DragonBits]

Alternatively, you could toss the middle measurement, in which case the half-life is calculated as 35 days, and the predicted peak is 1,930 ng/dL.

To throw some more numbers at this.

Recently I did a blood test at 17 days post injection Nebido now that I am at steady state. I was assuming my total T would be higher, wanted to see how high be didn't want to pay for LC/ms type of test.

Total T >1500, Free T 35.2, E2 37.4, I also did lipids which were unremarkable.

My estimate of Total T is 2120 based previous relationships of Free T and E2.

I have been feeling a little dizzy but I am thinking it might be DHEA which I recently measured at 598.2 (30.9 - 295.6 age adjusted range). DHEA range from labcorp for 22 yr male is (164.3−530.5. from somewhere else the range for 22 yr was (280 to 640). So my level is quite high.

Can't really tell my total T was so high and no changes in blood pressure.

I am reducing my DHEA, not entirely sure of the benefits of DHEA in any case, but I will reduce from 25 mg to 12.5 mg.