There are no known side effects of SAMe that would be related to worsening of prostate symptoms that I have heard of. However, each person’s body is unique and has the potential to generate different presentations of symptoms based on its individual chemistry. For example, SAMe can support certain detoxification reactions in the liver due to its nature as a methyl donor. If you are taking medication to control prostate symptoms there is a theoretical possibility that the SAMe is causing your body to metabolize and it excrete it faster. This is more usually the case with nutrients that specifically affect the cytochrome p450 systems of the liver like St. John’s Wort and grapefruit. SAMe is not on this list and has never been shown to affect medication metabolism but it is a theoretical possibility.
The other potential cause of how SAMe might be worsening your prostate symptoms relates to the second part of your question. As you body metabolizes SAMe a byproduct called homocysteine is produced. Homocysteine is known to cause inflammation in the body and most commonly associated with an elevated risk of heart disease. However, it is possible that it may cause inflammation in other areas of your body. To avoid this undesirable consequence of taking SAMe, it is advisable to take plenty of vitamin B6, B12(preferably as methylcobalamin) and folic acid. These nutrients support the mechanism that the body uses to recycle homocysteine into its inactive counterpart.
SAMe is a very valuable supplement and I will reiterate the point that it has never been shown to have any specific negative affects on the prostate. However, the chance of increasing homocysteine levels is real so I do advise a good B-complex supplement and folic acid be taken along with SAMe.