The creatine transporter is a sodium[139][140] and chloride[141][142] dependent membrane-associated transporter that belongs to the Na+/Cl-dependent family of neurotransmitter transporters.[143] In muscle cells and most other cell types,[131][141] the isomer of the creatine transporter is known as SLC6A8 (solute carrier family 6, member 8). SLC6A8 is encoded by the gene present on the Xq28 region of the human X-chromosome and is expressed in most tissues.[144] A related gene encoding a creatine transporter variant has also been identified at 16p11.1 that is expressed exclusively in the testes.[145] These two transporters share 98% homology.[144][145]
When endothelial cells have a higher creatine concentration, they appear to be mildly less permeable when incubated with 0.5-5mM creatine, while the higher concentration (5mM) is able to fully ablate TNF-α-induced neutrophil adhesion and both E-selectin and ICAM-1 expression.[316] This effect was prevented with ZM241385, an A2A (adenosine) receptor antagonist,[316] and since adenosine released by this receptor is known to be protective of endothelial cells,[317][318] it is thought that creatine works vicariously through this receptor and adenosine release, thought to be due to releasing ATP (occurs in response to stress[319][320]) which protects the cell via the A2A signaling system.[316]
Two of the immediate metabolites of testosterone, 5α-DHT and estradiol, are biologically important and can be formed both in the liver and in extrahepatic tissues.[155] Approximately 5 to 7% of testosterone is converted by 5α-reductase into 5α-DHT, with circulating levels of 5α-DHT about 10% of those of testosterone, and approximately 0.3% of testosterone is converted into estradiol by aromatase.[2][155][161][162] 5α-Reductase is highly expressed in the male reproductive organs (including the prostate gland, seminal vesicles, and epididymides),[163] skin, hair follicles, and brain[164] and aromatase is highly expressed in adipose tissue, bone, and the brain.[165][166] As much as 90% of testosterone is converted into 5α-DHT in so-called androgenic tissues with high 5α-reductase expression,[156] and due to the several-fold greater potency of 5α-DHT as an AR agonist relative to testosterone,[167] it has been estimated that the effects of testosterone are potentiated 2- to 3-fold in such tissues.[168]
In a mouse model of allergin-induced asthma, where mice were sensitized by ovalbumin for three weeks and then given 500mg/kg creatine, supplementation induced an increase in asthmatic hyperresponsiveness to low but not high doses of methacholine.[440] This hyperresponsiveness was associated with increased eosinophil and neutrophil infiltration into the lungs, and an increase in Th2 cell cytokines (IL-4 and IL-5) alongside an increase in IGF-1,[440] which is known to influence this process.[441] Interestingly, there was a nonsignificant increase in responsiveness in mice not sensitized to ovalbumin.[440]
Hopefully I didn’t put a big damper on your Captain-America fueled dreams! I just want to set proper expectations so you don’t get discouraged with slow progress, and instead get SUPER encouraged with any progress. Getting strong should be freakin’ fun! Weirdly enough, once I stopped trying to get there quickly is when I started to actually make permanent progress.

Creatine, the amino acid, naturally helps your body produce more adenosine triphosphate, or ATP, a small molecule that’s actually your body's primary energy source. But research shows that your body is only capable of storing enough ATP for 8 to 10 seconds of high-intensity exercise — and after that, it needs to produce new ATP for you to continue. (9)
In addition to being potentially harmful, some have argued that there is little evidence to indicate any benefit to using bodybuilding protein or amino acid supplements. "In view of the lack of compelling evidence to the contrary, no additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise".[18] In dispute of this, one more recent meta-analysis concluded that for athletes participating in resistance exercise training and consuming protein supplements for an average of 13 weeks, total protein intake up to 1.6 g per kg body weight per day would result in an increase in strength and fat-free mass, i.e. muscle, but that higher intakes would not further contribute. The muscle mass increase was statistically significant but modest - averaging 0.3 for all trials and 1.0 to 2.0 kg, for protein intake ≥ 1.6 g/kg/day.[3]
Creatine ethyl ester is more a pronutrient for creatinine rather than creatine,[74] and was originally created in an attempt to bypass the creatine transporter. It is currently being studied for its potential as a treatment for situations in which there is a lack of creatine transporters (alongside cyclocreatine as another possible example).[77] Its efficacy may rely on intravenous administration, however.
Hypogonadism is a disease in which the body is unable to produce normal amounts of testosterone due to a problem with the testicles or with the pituitary gland that controls the testicles. Testosterone replacement therapy can improve the signs and symptoms of low testosterone in these men. Doctors may prescribe testosterone as injections, pellets, patches or gels.
Eating the right carbs is important too. Carbohydrate is stored in your body in the form of glycogen. Glycogen in the muscles is an important fuel reserve during intense physical exercise or in times of energy restriction – protein sparing. It is best to restrict or to keep away from junk carbohydrates such as sweets, cakes, and biscuits, and stick to foods like porridge, pasta (wholemeal), rice (brown), bread (wholegrain), and cereals (try to choose the versions with low or reduced sugar and salt). For more on carbohydrate and the effect of sugar on the body, click here.
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