SERM's (Selective Estrogen Receptor Modulator) : These block certain estrogen receptors, ***ending on the drug, and dont actually lower estrogen in the blood. Estrogen is left to circulate with nowhere to go. Because of this, SERMS have a positive effect on cholesterol levels. They have a negative effect on IGF-1, so if bulking, only take them if totally necessary. They are good at blocking gyno. Commonly used during PCT, and less often used while cycling. A SERM like nolvadex is widely used in PCT to help kickstart the HPTA back to normal function, in conjunction with other beneficial drugs.
AI's (Aromatase Inhibitors) : There are 2 types of AI's. Type I (suicide inhibitor) attaches to the aromatase enzyme and permanently disables it. Type II compete for the enzyme, but dont destroy it. Both are effective at lowering estrogen substantially. Both are commonly used during both cycling and PCT. Used mainly when low estrogen levels are desired, like contest preparation/cutting. Beware that lowering estrogen with strong AI's can have a negative effect on cholesterol levels and low estrogen levels can lead to sore joints, cause your losing estrogens anti-inflammitory effect. Can also have a negative impact on your libido. Estrogen has an important role in mass building and joint health, as noted below where "estrogen" is explained.
RI's (Reductase Inhibitors) : These drugs stop the conversion of testosterone into DHT wherever 5-alpha reductase enzymes are present. RI's work by blocking the action of the 5-alpha. There are 2 5a's. Type I 5a and Type II 5a. Different RI's block one or both of these 5a's. The main reason someone uses RI's is to stop hair loss. They are common anti hairloss drugs. The problem is, when you block the dht conversion, there are less androgens available and may reduce your gains. Sometimes people report less strength, aggression and drive to train.
Estrogen : The first hormone we need to keep an eye on. Many AAS convert to estrogen via the aromatization process. Some AAS are worse than others. Also, estrogen spikes after a cycle. High levels of estrogen leads to gyno, water retention, fat storage etc. Estrogen plays a key role in progesterone related gyno. We either block its receptors with SERMS or reduce its production with AIs. We watch estrogen levels during a cycle and in PCT. Lowering estrogen too much will mess up your blood lipids. Letting it get out of control will cause sides like gyno, water retention etc. Estrogen plays a role in IGF-1 levels, may lower IGF-1 when blocked with a SERM. Estrogen is also beneficial hormone when bulking, promoting higher androgen receptor concentrations (!). It also is beneficial in another way - its supposed to act as an anti-inflammatory - this means blocking or reducing it too much during a heavy bulking cycle can result in injury to joints. Obviously different estrogen levels are desired for different goals, and it is not always good to block its action or its production. Usually, while bulking, estrogen is allowed to rise unless gyno or water retention (leading to high blood pressure) becomes a problem. When cutting and shedding water and lifting a little lighter (contest prep for example) estrogen is usually dropped with an AI. Proper diet and training can help the bad side effects high estrogen can have.
Progesterone : Its not so much progesterone that we watch, which is actually a healthy hormone, but progestins which may act upon its receptors. Progesterone, like Tren or Deca (nor-9's), may act on its receptor or lower progesterone in the blood. Gyno and lactating are more common side effects. Some people use progesterone receptor blockers to combat this, or a prolactin production inhibitor.
Cortisol : The third hormone, the stress hormone. When elevated to long, it will store fat. Eat muscle. Cause lethargy. Moodiness. You may crave carbs by the boat load. Cortisol spikes after a cycle because AAS blocks it while on cycle, upping cortisol production and receptor sites. IMO not enough attention is payed to this. It has special functions in the body that are absolutely necessary, like its anti-inflammatory ability. However, when elevated for long periods, it turns into a muscle eating beast. The most important time to watch cortisol is after a cycle, when it spikes. There are a couple ways to help control this, explained below. | 
Slin-Sane buy 2 get 1 FREE!!!!!
