DHEA levels plummet with aging. In fact, DHEA declines even more rapidly (on average) than either total or free testosterone, averaging 3% per year.  Furthermore, there is abundant evidence that low DHEA is associated with many medical conditions. But the acid test for any hormone is this: if you replace this hormone in those who are low or deficient, are significant benefits gained? For example, many studies show restoring youthful testosterone levels in low T men results in improved cardiovascular, psychological and insulin/diabetes parameters. But what about DHEA? Does DHEA Replacement Therapy yield comparable benefits?
As I will show below, I believe that DHEA packs close to the same hormonal punch in men and, when done properly, DHEA Replacement Therapy yields excellent results. (Consult your physicain or naturopath for your individual medical evaluation.). As I will show below, if a man is low in the first place, restoring more youthful levels of DHEA can do many of the same things that testosterone does. And many men feel that DHEA replacement is much more natural that testosterone therapies anyway, because DHEA is near the top of the hormone cascade.
Here are the Top Testosterone-Like Benefits of DHEA Replacement Therpay:
2. Increased Free Testosterone. Before I go into the medical benefits of DHEA, it is worth pointing out that DHEA will actually raise free testosterone in some men. Some hypogonadal men just do not like the idea of TRT. I was so miserable when I was low T that I never hesitated, but many men feel that it is unnatural, because it shuts down the body’s own production. And some men are concerned about side effects on HRT. DHEA may offer some of these men a reasonably effective alternative. This was shown in a study where DHEA was combined with HIIT. HIIT is basically what we used to call “interval training,” where you do a few rounds of max intensity for a minute or so followed by very low intensity for a few minutes. One study at least found that a combination of HIIT with 50 mg of DHEA twice daily produced significant increases in free testosterone with no real change in total testosterone. 
However, Ergo-log points out that the study found that the interval training actually contributed little or nothing to the rise in free testosterone and further points out that DHEA increased free testosterone in both the younger men in the 20’s and the older guys in their late 40’s.  Admittedly, the younger guys didn’t get as much of a boost proportionately, but they did get an increase. Now the older men approximately doubled their free testosterone on average and the effect lasted at least 24 hours. The authors of the study point out that free testosterone tends to fall faster than total testosterone and so the 40+ crowd seems ripe for a readjustment.
CAUTIONS: 100 mg per day is a large dose and furthermore is usually non-physiological. One should not take DHEA unless DHEA-S is low and one should not raise DHEA-S levels too high either. In other monitoring DHEA-S levels before and after is critical. I cover these here: Some Potential Dangers of DHEA. See my page on Inexpensive Hormone Testing Labs for testing.
LOW SHBG MEN: Some men are low SHBG due to, probably, liver dysfunction and insulin resistance. DHEA tends to lower SHBG and, if it did so in a low SHBG male, could cause issues. 
2. Insulin Sensitivity. One study looked at 28 men (and 28 women) seniors aged 65-78, all of which were verified to have age-related decreases in DHEA. In other words, they chose the perfect cohort to test DHEA supplementation. Furthermore, they gave the participants a fairly reasonable dose of 50 mg/day. The results were very impressive: the total area under the curve for insulin was significantly reduced, indicating a significant improvement in insulin sensitivity. 
This is reminiscent of testosterone, which lowers insulin levels and improves insulin sensitivity. This is one of the reasons that low testosterone is associated with increased risk for metabolic syndrome (prediabetes) and adult onset diabetes. See my pages Testosterone and Diabetes and Testosterone and Insulin for just how powerful this effect is.
It turns out that DHEA is also likely strongly protective against both prediabetes and adult onset diabetes as well according to some recent research. A number of animal studies have shown this, but let’s look first at a study on senior men and women with high cholesterol. In this study the researchers noted that DHEA significantly lowered insulin levels and increased insulin sensitivity.  However, they found that the area-under-curve for blood glucose was not changed. However, yet another study on senior men found the opposite: blood glucose levels were significantly lowered but insulin was not.  In spite of the contradiction, there seems to be growing body of research that DHEA can help some men with blood glucose and insulin control. NOTE: Not all studies show with DHEA show improvement in blood glucose and insulin control.
3. Youthful Mental Outlook. A 2009 study looked at a similar situation: middle and senior aged men and women and the researchers restored youthful levels. What they found was a greatly improved mental state:
This was associated with a remarkable increase in perceived physical and psychological well-being for both men (67%) and women (84%) ” 
4. Endothelial Function. This is a biggee for most men, since it can improve bedroom performance. Endothelial function refers to the ability of the inner lining of your arteries to relax via the release of nitric oxide. DHEA supplementation of 25 mg/day was shown to improve this in early senior men with high cholesterol. There is added weight to the validity of this study, because it was randomized, double-blind study. By the way, this study also validated #3 above and found improved insulin sensitivity.
Other studies have verifed the same and one at dosage of 25 mg/day as well.  How does it work this magic? It works on the same enzyme that Viagra and Cialis do and one set of researchers noted that “DHEA administration to human endothelial cells triggers nitric oxide synthesis, due to enhanced expression and stabilization of endothelial nitric oxide synthase (eNOS).”  Interestingly enough, standard HRT can also improve things in this way, since testosterone also activates eNOS. 
Now this is not going to be a massive effect, but every little bit of blood flow helps, eh?
5. Visceral (Stomach / Belly) Fat. The above study on seniors showed that visceral fat decreased significantly in seniors that took DHEA. And lowering visceral fat is a sign that insulin control is improving generally. Again, this is similar to HRT, which also has several studies showing it can often decrease visceral fat when give to hypogonadal men as well. See my page on Testosterone and Visceral Fat for more information. Testosterone can also lower subcutaneous fat according to some studies and DHEA did likewise in the same study. 
OTHER BENEFITS? There may be other benefits as well, and I have listed these below:
6. Anxiety. DHEA decreases anxiety for me significantly. It doesn’t do this for everyone, but I remember thinking a couple days after starting it, “So this is how normal people feel?”
7. Depression. Many men come to the Peak Testosterone Forum on SSRI’s, SNRI’s and other antidepressants. Of course, depression is very serious and, if you have to be on medications, then you just do. But keep in mind that one of the root causes for depression can be low brain hormone levels. Many men, inclduing myself, have seen depression vanish after getting on a good HRT protocol. Of course, it doesn’t always work that way, but some of us “get lucky.”
And it looks like low levels of DHEA could possibly be a root cause at times as well. For example, there are now several studies that show that DHEA supplementation can help with depression – even major depression. Check out these comments from journal articles for example:
“Depression ratings, as well as aspects of memory performance significantly improved. One treatment-resistant patient received extended treatment with DHEA for 6 months; her depression ratings improved 48 72% and her semantic memory performance improved 63%. These measures returned to baseline after treatment ended. In both studies, improvements in depression ratings and memory performance were directly related to increases in plasma levels of DHEA and DHEA-S and to increases in their ratios with plasma cortisol levels. These preliminary data suggest DHEA may have antidepressant and promemory effects and should encourage double-blind trials in depressed patients.” 
“These results suggest that DHEA treatment may have significant antidepressant effects in some patients with major depression. Further, larger-scale trials are warranted.” 
8. Morning Erections. As far as I know, there are no studies showing that DHEA improved nocturnal/morning erections. However, we have had a couple of reports on the Peak Testosterone Forum. Here is an example:
“Before that i was experimenting with 50mgs of DHEA, after a week or 2 I noticed morning erections, that were rock hard, the last time i had this was when I was a teenager. I also noticed I was able to concentrate better and seemed to have more energy, when playing darts, and was able to score better and felt more enhusiastic. I am a FPS gamer and i seemed to improve no end when gaming also. I had to stop taking it doctors orders for a few weeks to get my T levels done. I have been off it about 3 weeks and up until a few days ago I was still getting morning wood.” 
9. Inexpensive. You can buy a six month supply of DHEA for around $14.00 (at 50 mg per day) on Amazon. And some experts argue for even lower dosages between 5 and 25 mg and, in that case, you’ve got a year’s supply at that cost! Even the cheapest of HRT clinics will cost you several hundred dollars per month for testing, injections and so on.
CAUTION: Do not quit any medication, especially an antidepressant, without discussing it with your physician first.
CONCLUSION: Is DHEA as good as HRT (TRT)? My impression on the forum is that, generally speaking, it lacks the power that testosterone has for the typical hypogonadal male. Nevertheless, DHEA seems to work very well for some guys and so, considering it’s low cost, may be worth a try.
1) Eur J Appl Physiol, 2013 Jul, 113(7):1783-92, “Effect of acute DHEA administration on free testosterone in middle-aged and young men following high-intensity interval training.
3) Clin Endocrinol (Oxf), 1998 Oct, 49(4):421-32, “The effect of six months treatment with a 100 mg daily dose of dehydroepiandrosterone (DHEA) on circulating sex steroids, body composition and muscle strength in age-advanced men and women”
4) Endocrinology, 151(4), Published Online Jul 1 2013, “Androgen Receptor-Dependent Activation of Endothelial Nitric Oxide Synthase in Vascular Endothelial Cells: Role of Phosphatidylinositol 3-Kinase/Akt Pathway”
5) Biological Psychiatry, Feb 1997, 41(3):311 318, “Dehydroepiandrosterone (DHEA) treatment of depression”
6) Psychiatry Online, Apr 1999, 156(4):646-649 Next Article”Double-Blind Treatment of Major Depression With Dehydroepiandrosterone”
7) JAMA, Nov 10 2004, 292(18), “Effect of DHEA on Abdominal Fat and Insulin Action in Elderly Women and Men: A Randomized Controlled Trial”
8) JAMA, Nov 10 2004, 292(18), “Effect of DHEA on Abdominal Fat and Insulin Action in Elderly Women and Men: A Randomized Controlled Trial”
9) JCEM, First Published Online: January 14, 2009, 78(6), “Effects of replacement dose of dehydroepiandrosterone in men and women of advancing age”
9) International Journal of Obesity, 1990, 14(5):457-463, “Lack of effect of dehydroepiandrosterone in obese men”
10) Systems Biology in Reproductive Medicine, 1998, 40(2):87-93, “Andropause and the Aging Male”
11) JAMA, 2004 Nov 10,292(18):2243-8, “Effect of DHEA on abdominal fat and insulin action in elderly women and men: a randomized controlled trial”
13) JCEM, Published Online: Jul 02 2013, “Dehydroepiandrosterone Supplementation Improves Endothelial Function and Insulin Sensitivity in Men”
14) Endocrinology, 144(8), Published Online: July 01, 2013, “Dehydroepiandrosterone Modulates Endothelial Nitric Oxide Synthesis Via Direct Genomic and Nongenomic Mechanisms”
15) JCEM, 88(7), First Published Online: April 26, 2011, “Dehydroepiandrosterone Supplementation Improves Endothelial Function and Insulin Sensitivity in Men”