Both genetic and environmental factors contribute to neurodegenerative disorders. In a large number of neurodegenerative diseases (for example, Alzheimer's disease (AD)), patients do not carry the mutant genes. Other risk factors, for example the environmental factors, should be evaluated. 17β-trenbolone is a kind of environmental hormone as well as an anabolic-androgenic steroid. 17β-trenbolone is used as a growth promoter for livestock in the USA. Also, a large portion of recreational exercisers inject 17β-trenbolone in large doses and for very long time to increase muscle and strength. 17β-trenbolone is stable in the environment after being excreted. In the present study, 17β-trenbolone was administered to adult and pregnant rats and the primary hippocampal neurons. 17β-trenbolone's distribution and its effects on serum hormone levels and Aβ42 accumulation in vivo and its effects on AD related parameters in vitro were assessed. 17β-trenbolone accumulated in adult rat brain, especially in the hippocampus, and in the fetus brain. It altered Aβ42 accumulation. 17β-trenbolone induced apoptosis of primary hippocampal neurons in vitro and resisted neuroprotective function of testosterone. Presenilin-1 protein expression was down-regulated while β-amyloid peptide 42 (Aβ42) production and caspase-3 activities were increased. Both androgen and estrogen receptors mediated the processes. 17β-trenbolone played critical roles in neurodegeneration. Exercisers who inject large doses of trenbolone and common people who are exposed to 17β-trenbolone by various ways are all influenced chronically and continually. Identification of such environmental risk factors will help us take early prevention measure to slow down the onset of neurodegenerative disorders.
Tibolone has tissue -selective estrogenic effects, with desirable effects in bone , the brain , and the vagina , and lack of undesirable action in the endometrium and breasts .  Its tissue selectivity is the result of metabolism , enzyme modulation (., of estrogen sulfatase and estrogen sulfotransferase ), and receptor modulation that vary in different target tissues, and differs mechanistically from that of selective estrogen receptor modulators (SERMs) such as tamoxifen , which produce their tissue-selectivity via means of modulation of the ER.   As such, to distinguish it from SERMs, tibolone has been described as a "selective tissue estrogenic activity regulator" (STEAR),  and also as a "selective estrogen enzyme modulator" (SEEM). 
Trenbolone is as strong of an androgen as it is an anabolic, where its androgenic strength is also that of five times the strength of Testosterone. With an androgenic rating of 500, it is commonly known that Trenbolone can and does exhibit increased feelings of irritability and aggression in most users. This side effect is very dose-dependent, with more pronounced aggression seen in higher (and often unnecessary) Trenbolone doses. Various individuals will also not experience tis side effect at all as a result of their individual response. Users who are known to have short temper and anger-control issues prior to Trenbolone use should exercise extreme caution, as the use of Trenbolone can and will without a doubt cause an amplification of these traits. Such individuals should avoid Trenbolone use as a responsible decision. As a general overall rule, any and all Tren users should always exercise caution and ensure that a proper stable psychological state is always maintained, and that the user be constantly aware of their actions at all times. Appropriate discipline is of the utmost importance when utilizing any anabolic steroid, especially Trenbolone (and special considerations must be taken at higher doses). It must be made crystal clear to the reader that the use of any type of drug is absolutely no reason for any individual to absolve themselves of all personal responsibility, and shift the blame onto the drug in question (in this case, Trenbolone) when the user commits a regrettable action. Remember this at all times!