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balance of enzyme production between 5alpha-reductase and 20alpha-hydroxysteroid oxidoreductase and 3alpha(beta)-hydroxysteroid oxidoreductase play role in carcinogenesis and proliferation in the balance of production of progesterone metabolites. The 5alpha pregnenes are pro carcinogenic  and the 4-pregnenes are anti carcinogenic.

Saw Palmetto inhibits 5alpha reductase activity.  This study looked at the inhibition of Saw Palmetto of 5alpha reductase activity in prostate cancer.  Saw Palmetto is also known as Serenoa repens.

Breast cell culture study finds increase 5alpha-reductase 1/2 activity and decreased 3alpha HSO.  This fits previous previous studies that show that increased 5alpha pregnanes is associated with increased proliferation and increased detachment; in contrast to decreased 4-pregnene metabolites.

cell culture study finds that increased 5alpha reductase activity and resultant 5alpha-pregnanes are associated with breast cancer cell lines.  This is in contrast to the 4-pregnenes.  In fact, decreased 4-pregnenes are found in the same breast cancer cell lines; this suggests decreased 20alpha-HSO and 3alpha-HSO activity.

Transdermal progesterone levels are quickly transported to saliva.  This quick transport, while serum doesn't equally reflect progesterone, has puzzled many.  Theories have been proposed, yet no answers.   This study looked at whether 5alpha reductase expression in the skin would metabolize the progesterone  and this explain the difference in the two test mediums.  The authors of this study concluded that 5alpha reductase is the not the reason for the difference found in saliva and serum.  the same can be applied to urine as well.

Awesome article on progesterone metabolism in breast cancer.  The author, weibe, describes 2 categories of progesterone metabolites in breast tissue: 5alpha-pregnanes and 4-pregnenes.  The author describes 3 primary enzymes that control the balance between these 2 metabolites--5alpha reductase, 3alpha-HSO, and 20alpha-HSO.  The resultant balance of 5alpha-dihydroprogesterone and 3alpha-dihydroprogesterone helps to determine the cancer potential of breast tissue.

5alpha-reductase PCOS.  Insulin and obesity are associated with increased 5alpha-reductase activity.

Cell culture study finds that 5alpha-reductase inhibition decreased 5alpha-pregnanes and thus inhibited cell proliferation and detachment; this is in contrast to the 4 pregnenes that occur through the enzymes 3alpha-hydroxysteroid oxidoreductase and the 20alpha-hydroxysteroid oxidoreductase, which show anti cell proliferation and cell detachment.

Saw Palmetto show to inhibit 5alpha reductase activity in prostate cancer cells.

Interesting abstract of study of DHEA metabolites.  In vivo study finds some DHEA metabolites inhibit 5-alpha-reductase activity.  The opening sentence implies that 5alpha-reductase and conversion of T to DHT promotes androgen dependent disease.  The inference here is cancer, however, what they fail to mention is that this activity is via the estrogen receptors.

Might the enzymes be more important than the hormones themselves?  The number is important i.e. progesterone, but how the number came to be is more important as it points to the underlying etiology.  Here, the balance of enzymes are found to direct cell line tumor potential.  The enzyme 5alpha-reductase increased production of the 5alpha-pregnanes which increased tumor potential.  In contrast, the enzymes 20alpha-hydrosteroid oxidoreductase and 3alpha-hydroxysteroid oxidoreductase increase production of the 4alpha-pregnanes, which decreased tumor potential.

Nice review of the inherent risks associated with 5alpha-reductase inhibition therapy.

5alpha reductase inhibitors associated with decreased risk of Gleason 2-7 prostate cancer in men with LUTS and enlarged prostate.

Saw Palmetto extract found to be potent inhibitor of 5alpha reductase activity.   Inhibition was 61%.  This study looked at the inhibition in those men with BPH.

Study finds Saw Palmetto inhibits 5alpha reductase activity enough to show improvement in those with alopecia (hair loss).

Progesterone is proposed as a therapy in prostate cancer.   The mechanism is due to the inhibition of 5alpha reductase activity.

Progesterone to inhibit 5alpha reductase in men.

5 alpha reductase inhibitor, finasteride inhibits pro-tumor progesterone metabolite pathway.

Great read on the regulation of the androgen receptor by the different iso forms of 5-alpha reductase and HSD.

Nice review of the mixed data on Testosterone and Prostate disease. It is clear that Testosterone does not precipitate prostate cancer.  The intraprostatic hormone milieu likely is different than that present in the serum.  No surprise there.  5alpha reductase decreases prostate volume, PSA, and low-grade prostate cancer, but actually increases aggressive prostate cancer. Supraphysiologic doping in young men associated with no increase in prostate disease. PSA no longer to be followed in men < 55.  Mortality rate not changed.  PSA change of 1.4 ng/ml is appropriate for additional prostate evaluation.  Testosterone therapy on average increased 0.5 ng/ml. Still, no mention of aromatase activity in this article.  Why is it that hormone sensitive disease in men is only with regards to androgens and women estrogen.