Testosterone Replacement Therapy (TRT) has been a large success to date and improved the lives of many hypogonadal men (such as myself), so why not some of the other hormones? DHEA is an example of a hormone with considerable promise. One study shows, that when combined with HIIT (High Intensity Interval Training), it can boost free testosterone levels substantially. (See my page How to Increase Your Testosterone Levels Naturally for details.) And, as I mentioned in my page on How to Increase DHEA, we had one man claim that DHEA restored his morning erections. And DHEA seems to have very powerful anti-diabetes, anti-Metabolic Syndrome properties.
So DHEA definitely has some excellent properties, but is there a dark side? I think the argument is weak against DHEA, assuming it is taken within physiological dosages. To protect against taking too much, what I see the savvy doctors doing is the following:
a) Testing a man’s DHEA-S first and making sure he is in the lower part of the lab’s range. Many men are actually high in DHEA-S, so taking DHEA makes no sense in that case.
b) Giving a man low dose (usually oral) DHEA-S in order to hit a DHEA-S target that is usually in the upper mid range of DHEA-S.
c) Making sure with continuted monitoring that the man does not go too high in DHEA-S on an ongoing basis.
I believe the above precautions will avoid almost all problems, but, of course, it’s always best to consult with a physician or naturopath first.
NOTE: A combination of DHEA and pregnenolone got rid of my lifelong struggle with some anxiety. Read more about here: Low Dose DHEA and Pregnenalone.
1. Arrhythmia. Ray Sahelian has stated that many users of DHEA, especially in medium and higher dosages, have experienced arrhythmias.  It is too early to tell in what subpopulations and circumstances this occurs. Adding to the confusion is the fact that one study showed that the higher the (non-supplemented) levels of DHEA, actually DHEA-S, the lower the risk of atrial fibrillation, which is the most common kind of arrhythmia.  However, the fact that someone naturally has high levels of DHEA does not necessarily equate to the same physiological situation as someone being low and then supplementing. An underlying, predisposing condition could remain. Or it could be that those who are already high and supplement occasionally have an arrhythmia.
2. Negative Brain Effects? Ray Peat warns against overly elevated DHEA levels:
“One study has found that the only hormone abnormality in a groupt of Alzheimers patients’ brains was an excess of DHEA. In cell culture, DHEA can cause changes in glial cells resembling those seen in the aging brain. These observations suggest that DHEA should be used with caution. Supplements of pregnenolone and thyroid seem to be the safest way to optimize DHEA production.” 
Again, holding DHEA-S levels to mid range values should alleviate these kind of concerns, but keep in mind that there are no long term studies with DHEA that I know of.
3. Possible Increasing PSA?. In general, DHEA is thought to be anti-cancer. However, there are reports of men taking DHEA who have spiked their PSA’s.  Is this coincidence? Well, without some study work, it is difficult to say. But you may want to take your PSA before and after to make sure. And, if you have had issues with your PSA, discuss with your doctor. Again, this should not be an issue with the lower dosages that I am used to seeing. See my page on DHEA Dosages for more information.
4. Possible Gynecomatia. The steroid boards have quite a few posts of men getting gyno from taking larger doses of DHEA. However, from what I can tell, this is from taking very large dosages of DHEA – 500 mg +.
5. Increased IGF-1. DHEA has done fairly well in the cancer studies from what I have read. However, one distrubing property: it increases IGF-1. IGF-1 is the growth factor that is ground zero for a lot of anti-aging research, i.e. elevated IGF-1 levels are associated with accelerated aging. In addition, abundant research shows that higher levels tend to fuel epilthelail cancers and adult onset diabetes. Of course, one would not want to go too low since IGF-1 is anabolic and supports many key metabolic processes. In any event, there are several studies that show that DHEA supplementation increases IGF-1 in men.  The good news is that it seems to minimally raise IGF-1, assuming one is using a reasonable dose <= 25mg. I discuss that the research that shows in my page on DHEA and IGF-1.
FINAL COMMENT: Many experts point out that the great majority of side effects with DHEA occur at higher dosages. For this reason, they recommend much lower dosage of DHEA, such as Ray Sahelian who believes 5 mg is the most appropriate dosage considering our bodies only make 10-15 mg/day probably..
NOTE: Keep in mind that most people who take DHEA do not test to see if they are low. You can test your DHEA levles very inexpensive here: Inexpensive Testing Labs (Mostly U.S.). I make this comment, because boosting a little very low DHEA levels is probably a different thing that a man with high levels pushing his DHEA even higher. Deficiencies usually need correcting and pushing yourself supraphysiological is often not a good thing when it comes to hormones.
5) Eur J Prev Cardiol. 2014 Mar;21(3):291-8, “Dehydroepiandrosterone sulfate levels and risk of atrial fibrillation: the Rotterdam Study”
6) The Journal of Clinical Endocrinology & Metabolism, Published Online: July 01, 2013, “Effects of replacement dose of dehydroepiandrosterone in men and women of advancing age.”