If you were injecting straight testosterone then having it encounter and interact with more aromatase in fatty tissue would at least be a theoretical possibility. However, testosterone esters such as testosterone cypionate are essentially inert at the injection sites; they cannot be aromatized. Instead they must be absorbed, and only when they reach the bloodstream do they encounter enzymes that strip off the esters, leaving the biologically active testosterone free to interact with aromatase, SHBG, androgen receptors, etc.
The absorption mechanisms for subcutaneous and intramuscular injected depots are somewhat different. This leads to differing rates of absorption, which in turn are reflected in differing levels of serum testosterone over time. The data suggest that in general IM depots absorb faster than SC depots. This means that serum testosterone with IM goes up faster and higher, but also drops sooner and lower. You get higher peaks and lower troughs, but overall the same amount of testosterone is delivered at the same dose, so that average levels are the same between IM and SC. The differing serum levels are reflected in metabolites such as estradiol. The expectation is that at pre-injection troughs the level of estradiol is higher with SC injections than with IM injections. However, the opposite is expected at peak serum levels.
Vince
Super Moderator
I do both shallow IM and Sub q. Before I only did shallow. And forever reason both my E2 and HCT went lower.
madman
Super Moderator
Whether injected strictly IM or sub-q the esterified T (prodrug) does not aromatize to estradiol until the ester has been cleaved which mainly happens when it enters the bloodstream as you are then left with native/free T.
*PRODRUG HYDROLYSIS occurs in the blood and the ester is also partly hydrolyzed within the interstitium"
Then the magic happens as some will be bound to binding proteins (SHBG, HSA, cortisol-binding globulin, and orosomucoid, binding/activation of androgen receptors, converted by the 5α reductase enzyme to DHT and aromatized to estradiol.
I would be more concerned with your protocol (dose T/injection frequency) let alone where your FT level sits than fretting over injecting IM vs sub-q!
NEW INSIGHTS INTO DRUG ABSORPTION FROM OIL DEPOTS (2017)
CONCLUSIONS
It is interesting to realize that drug absorption from an oil depot cannot entirely be described by a simple two-phase mass transfer model where concentration gradients, diffusion, and partition coefficients would enable the calculation of the expected absorption. It is demonstrated in this dissertation that there is a role of the excipient BOH in yielding an initially high absorption. The oil depot forms a continuous phase after injection but will be dispersed and encapsulated at the injection site after some days. This in turn largely influences the way the prodrug becomes available; after release from the oil depot, it is present in the interstitial fluid which is drained through the lymph into the systemic circulation. Subsequently, the prodrug permeates through the wall of blood cells and is hydrolyzed. Both the lymph transport and the cell wall permeation take time which is expressed in a lag time.
This lag time is different for each injection site: a subcutaneously administered prodrug will enter the systemic circulation via a short path and at a low drainage flow. This results in a short lag time and a slow absorption rate constant of the prodrug.
Deeper administered prodrugs (i.e. intramuscular injections) are suggested to be absorbed via a longer path, but at a higher flow, which results in a longer lag time but a higher absorption rate constant of the prodrug.
Figure 7.2: Schematic overview of the new insights into drug absorption from oil depots. After release from the oil depot (yellow circle at the injection site), the prodrug is transferred towards the central compartment via the lymphatic system. Here, it will be hydrolyzed to the active substance (see circle). ka = absorption rate constant; ke = elimination rate constant.
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B) Schematic illustration of the absorption steps of testosterone esters after IM (left) or SC (right) injection. With administration using either route, the ester exits the depot via diffusion into the interstitium from where it enters the lymphatics and subsequently reaches the circulation where it undergoes hydrolysis by intracellular esterases. Testosterone ester is also partly hydrolyzed within the interstitium, with free testosterone entering the circulation directly.
IM (intramuscular)
SC (subcutaneous)
*PRODRUG HYDROLYSIS occurs in the blood and the ester is also partly hydrolyzed within the interstitium"
Then the magic happens as some will be bound to binding proteins (SHBG, HSA, cortisol-binding globulin, and orosomucoid, binding/activation of androgen receptors, converted by the 5α reductase enzyme to DHT and aromatized to estradiol.
I would be more concerned with your protocol (dose T/injection frequency) let alone where your FT level sits than fretting over injecting IM vs sub-q!
NEW INSIGHTS INTO DRUG ABSORPTION FROM OIL DEPOTS (2017)
CONCLUSIONS
It is interesting to realize that drug absorption from an oil depot cannot entirely be described by a simple two-phase mass transfer model where concentration gradients, diffusion, and partition coefficients would enable the calculation of the expected absorption. It is demonstrated in this dissertation that there is a role of the excipient BOH in yielding an initially high absorption. The oil depot forms a continuous phase after injection but will be dispersed and encapsulated at the injection site after some days. This in turn largely influences the way the prodrug becomes available; after release from the oil depot, it is present in the interstitial fluid which is drained through the lymph into the systemic circulation. Subsequently, the prodrug permeates through the wall of blood cells and is hydrolyzed. Both the lymph transport and the cell wall permeation take time which is expressed in a lag time.
This lag time is different for each injection site: a subcutaneously administered prodrug will enter the systemic circulation via a short path and at a low drainage flow. This results in a short lag time and a slow absorption rate constant of the prodrug.
Deeper administered prodrugs (i.e. intramuscular injections) are suggested to be absorbed via a longer path, but at a higher flow, which results in a longer lag time but a higher absorption rate constant of the prodrug.
Figure 7.2: Schematic overview of the new insights into drug absorption from oil depots. After release from the oil depot (yellow circle at the injection site), the prodrug is transferred towards the central compartment via the lymphatic system. Here, it will be hydrolyzed to the active substance (see circle). ka = absorption rate constant; ke = elimination rate constant.
TRT with Subcutaneous Testosterone Injections: A Safe, Practical and Reasonable Option
Abstract Context: Injections with intramuscular testosterone esters have been available for almost 8 decades and not only result in predictable serum testosterone levels but are also the most inexpensive modality. However, they are difficult to self-administer and associated with some...
www.excelmale.com
B) Schematic illustration of the absorption steps of testosterone esters after IM (left) or SC (right) injection. With administration using either route, the ester exits the depot via diffusion into the interstitium from where it enters the lymphatics and subsequently reaches the circulation where it undergoes hydrolysis by intracellular esterases. Testosterone ester is also partly hydrolyzed within the interstitium, with free testosterone entering the circulation directly.
IM (intramuscular)
SC (subcutaneous)
Smokin Joe
Active Member
Interesting thread.
I am trying Sub q right now for the first time consistently.
About 7 weeks.
I don't know about my e2 bit I have become meaner than a junkyard dog! Very impatient and short fused.
It appears that there is a metbolization factor at work here.
I never felt this way on injections.
Going to switch soon to see if it helps.
I am trying Sub q right now for the first time consistently.
About 7 weeks.
I don't know about my e2 bit I have become meaner than a junkyard dog! Very impatient and short fused.
It appears that there is a metbolization factor at work here.
I never felt this way on injections.
Going to switch soon to see if it helps.
If you're doing daily you need to lower your dose
Smokin Joe
Active Member
20mg end for a total of 80mg weekly.
Smokin Joe
Active Member
EOD.
My bad.
My bad.
Did you have same dose and schedule with IM?
Smokin Joe
Active Member
IM schedule was a 4/3.
40mg 2 times weekly.
40mg 2 times weekly.
Have you gotten bloodwork to compare?
Smokin Joe
Active Member
Not yet at just 7 weeks bit may just switch back to I'm first.
Undecided.
Undecided.
Systemlord
Member
Smokin Joe
Active Member
I think the same for me as far as experience goes.
I might do some bloodwork just see whT e2 is.
I might do some bloodwork just see whT e2 is.
But with subQ you felt high e2 symptoms?
Cyclingislife
New Member
I switched to SQ for a few months. Yes the injections are easier. But I never felt as “good” as I do on IM even though my labs were similar. But everyone is different, you have to test things to see what works best, some guys love SQ. I think IM just absorbs better for me & I can stay in my sweet spot. I have lower SHBG and it took me a year to dial it in. My current protocol is 20mg cypionate EOD, no AI and it’s been a game changer. My SHBG actually went up from 16 to 19. I inject with 27 gauge insulin needles only in my shoulders, it’s virtually painless. I also only eat between noon - 8pm. I think that also helps for any low SHBG guys out there.
Systemlord
Member
Smokin Joe
Active Member
27 guage by what length?
I've been using a 3/16ths.
I've been using a 3/16ths.
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