5 alpha reductase

The enzyme 5 alpha reductase is responsible for converting part of the testosterone in men into the most potent and active masculine hormone DHT (dihydrotestosterone). Finasteride acts in the body by inhibiting the action of 5 alpha reductase enzyme. There are two types of this enzyme: type I and type II (recent studies indicate the possible existence of type III as well). While Finasteride inhibits the activity of 5 alpha reductase type II, dutasteride inhibits both types. 5 alpha reductase enzymes are present throughout the body at the cellular level. They perform various functions. There is a very common misunderstanding regarding the activity of finasteride in the body. Most men have the impression that finasteride will act only on the scalp, inhibiting DHT convertion on site, preventing follicle miniaturization. However, being an oral drug, blood will take finasteride throughout your body, inhibiting the activity of the enzyme 5 alpha reductase in the brain, skin, prostate, endocrine glands, etc.. To make matters worse, Finasteride is considered an irreversible  5 alpha reductase inhibitor. For irreversible, it is understood that after taking the drug, even after stopping, these enzymes which have been blocked do not return to activity anymore. Does the body replace them or does the body adapt? 

Perhaps in these questions lie the answers to why some men suffer with persistent effects and others do not ... It may be the body's ability to replace the activities of 5 alpha or produce new enzymes. Perhaps in some individuals, this process is not fully reversed, causing persistent effects.

And what is the importance of the activities of the 5 Alpha Reductase for the proper functioning of the body?
This enzyme acts in the conversion of hormones into other hormones. So, without the activity (or other mechanism to replace that activity), the body stops producing essential substances. Functions of the enzyme 5 alpha reductase: 

1. Conversion of testosterone into DHT 
DHT or dihydrotestosterone is the most potent and erogenous form of testosterone. Exerts major role in male sexuality. Read about the importance of DHT on the previous page. 

2. Conversion of progesterone to allopregnanolone . 
Men also secrete progesterone, only in much smaller quantities than women. Part of progesterone is converted by 5 alpha reductase into allopregnanolone. This substance (allopregnanolone) acts on the brain, modulating (stimulating) the neurotransmitter known as GABA-A. GABA-A brings feeling of safety, calmness, relaxation (including muscle relaxation) to the individual. When a person takes a tranquilizer for example (as benzodiazepines) the goal is to increase the amount of GABA-A in the brain, and take the person out of a panic attack or treat chronic anxiety. Finasteride triggers the opposite effect in some men ... it decreases the production of allopregnanolone, and consequently the level of GABA-A in brain. It is the action of allopregnanolone, which allows relaxation when a person ingests an alcoholic beverage. This effect disappeared in patients who developed Post-Finasteride Syndrome. Not coincidentally, finasteride is being tested in the U.S. in alcoholics. See studies on the following page. 

3. Intense activity in the skin. 
The highest concentration of 5 alpha reductase in the body is the skin. And in the whole skin, the largest concentration of 5 alpha reductase is the head of the penis. The glans has a huge amount of activity of 5 alpha reductase ... I remember I read an interesting analogy some time ago, that an area the size of a pinhead on the skin of the penis has more activity of 5 alpha reductase than the rest of the body skin combined. Remember that this enzyme converts testosterone into DHT, a hormone that is five times more erogenous than testosterone. It is obvious that this organization of the body is not for nothing. Probably the glans needs all this 5ar activity (the conversion of testosterone into DHT) to promote pleasure in the sexual act. And coincidentally, one of the biggest complaints of men who suffer from Post-Finasreride Syndrome is the loss of sensation in the glans. There are also complaints about reduced sensitivity in the skin in general and very dry skin. 

4. Bile acid biosynthesis. 
Bile acid is composed of acidic steroids. It is synthesized by oxidation of cholesterol. 5 alpha reductase operates in the production of bile acid, which is essential in the digestion of fats. It is noteworthy that many patients with Post-Finasteride Syndrome complain of digestive problems and increased cholesterol levels after the use of Finasteride. See study on cholesterol increase and Finasteride on the next page 

5. Metabolism of estrogen in women.  5 alpha reductase is directly involved in the metabolism of estrogen in women. This is another reason why women should not use Finasteride.