Some bodybuilders and athletes use trenbolone esters for their muscle-building and otherwise performance-enhancing effects.  Such use is illegal in the United States and many other countries. The DEA classifies trenbolone and its esters as Schedule III controlled substances under the Controlled Substances Act .  Trenbolone is classified as a Schedule 4 drug in Canada  and a class C drug with no penalty for personal use or possession in the United Kingdom .  Use or possession of steroids without a prescription is a crime in Australia .  The infamous "duchess" cocktail administered to Russian athletes at the Sochi Winter Olympics consisted of oxandrolone , a metenolone ester, and a trenbolone ester. 
Tren is an extremely androgenic hormone, and as a result well known for promoting androgenic side effects. Hair loss and acne in men who are predisposed are both possible. Body hair growth is also possible. If you are not genetically predisposed no amount of Tren on earth with cause these issues. The androgenic side effects of Tren are truly based on genetic response. When it comes to hair loss, if you are predisposed to male pattern baldness, meaning at some point you’re going to lose your hair regardless of steroid use , Tren is one of the fastest ways to ensure you lose your hair a little sooner.
Virilization is a serious androgenic side effect of Tren. It is very difficult for a woman to use Tren without some level of virilization and makes it a steroid that’s almost never recommended for female use.
Important Note: The 5-alpha reductase enzyme does not metabolize the Trenbolone hormone. This means 5-alpha reductase inhibitors like Finasteride will not affect the androgenicity of the hormone.
The most important aspects to understand about Trenbolone are the Trenbolone exclusive side effects. It is the most potent and anabolic steroid available, but it can also bring with it the most adverse side effects. The intent is not to dissuade anyone from taking Tren, as with anything, the more knowledge we have about an aspect of our lives, the better we can navigate toward our ideal lifestyle. I have watched people take 1000mg a week of tren alone, enamored with the physical results, but not understand why, at the same time as this physical supremacy, their lives start falling apart. Their relationships with their wives or girlfriends are strained, they uncharacteristically start going through the significant other’s phone with sudden onset of paranoia. Days at work are rife with anxiety and exhaustion from lack of sleep. I myself have gotten out of a car at a stoplight with a sudden onset of blind rage because someone beeped at me. These side effects can occur, and if you don’t attribute them to the tren, if you don’t realize it is the tren causing these reactions, then you will just keep doing the same regimen of tren as your life slowly goes downhill. Always add some test to a tren cycle, that can mitigate some of the side effects especially improving libido. If you start noticing some of these sides, the best thing to do is to lower the amount you are taking. Find the max amount you can take without suffering from the side effects. I recommend to most to keep it around 300mg-400mg a week.