Marijuana extracts possess the effects like the endocrine disrupting chemicals.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Search&term=%22Watanabe+K%22%5BAuthor%5DDepartment of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Hokuriku University, Ho-3 Kanagawa-machi, Kanazawa 920-1181, Japan.
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The progesterone 17alpha-hydroxylase activity, which is one of the steroidogenic enzymes in rat testis microsomes, was significantly inhibited by crude marijuana extracts from Delta(9)-tetrahydrocannabinolic acid (THCA)- and cannabidiolic acid (CBDA)-strains. Delta(9)-Tetrahydrocannabinol, cannabidiol and cannabinol also inhibited the enzymatic activity with relatively higher concentration (100-1000 microM). Testosterone 6beta- and 16alpha-hydroxylase activities together with androstenedione formation from testosterone in rat liver microsomes were also significantly inhibited by the crude marijuana extracts and the cannabinoids. Crude marijuana extracts (1 and 10 microg/ml) of THCA strain stimulated the proliferation of MCF-7 cells, although the purified cannabinoids (THC, CBD and CBN) did not show significant effects, such as the extract at the concentration of 0.01-1000 nM.
These results indicate that there are some metabolic interactions between cannabinoid and steroid metabolism and that the constituents showing estrogen-like activity exist in marijuana.
PMID: 15588936 [PubMed - indexed for MEDLINE]
There is a lot to say about this, a quick survery of PubMed will show that. That is, some have suggested that the results from smoking marijuana are not the same as if an extract is utilized. Others consider that marijuana may be indirectly, rather than directly, responsible for estrogen increases, estrogenic effects, lowered LH, and/or some combination or variation of these observed effects.
Ultimately, I don't feel I can make a solid judgement on the subject, that is, to say a certain thing is fact and another may be fiction, however, what is clear is that marijuana usage certainly has its effects and the ones under consideration, even debate, are nearly all such as would be of major concern to me if I were a smoker and using certain muscle building/performance enhancing agents or undergoing a period of PCT.