First, the following disclaimer: Products that are sold as supplements (as opposed to medications) are not regulated by the Food and Drug Administration so they are not tested for safety, efficacy or standardization.  In other words, when you buy a supplement, there is no guarantee that what is in the bottle has been tested to see if it even contains the ingredient in question, let alone whether the ingredient actually does what it claims to.  (That’s not a value judgment, just the facts.)
Deer velvet might have an effect due to the hormones it may contain, including testosterone, androstenedione, and dehydroepiandrosterone. Research in rats, using elk velvet antler, suggested the substance may have an androgen-like effect. The antlers are ground into powder, which people take by mouth. Dosage varies by brand, but a recent study used 215 mg per day. Some distributers, though, recommend dosages ranging from 250 mg to as high as 3000 mg (3 g) per day. So talk with your doctor before you start using deer velvet.
Deer antler velvet can help slow the aging process and possibly even increase longevity due to the IGF-1 present in deer antler velvet. Aging occurs because our DNA becomes damaged throughout our lives and the damages accumulate over time. The damaged nuclear DNA can either directly cause the aging process by increasing cell dysfunction or it can indirectly cause the aging process by increasing programmed cell death (apoptosis) or increasing the number of cells which are unable to divide any further (cell senescence).
Unfortunately, the potential problems with IGF would seem to negate any of these theoretical benefits.  It has been shown that improper use of hormones such as dehydroepiandrosterone (DHEA), androstenedione, and human growth hormone may increase the risk for development of prostate cancer or promote the growth of existing prostate cancer by raising IGF-1 levels.  Therefore, men who are taking supplements with IGF in it (or those that raise IGF levels) could theoretically be putting themselves at an increased risk for prostate cancer.  Again, it hasn’t been rigorously studied so it’s impossible to know for sure, but if you have any risk factors for prostate cancer, it’s probably best to avoid taking this supplement.  
A systemic review on human interventions[25] makes note of a study conducted on patients of osteoarthritis (Edelman et al. 2000; cannot be located online) which found improvements in joint pain symptoms relative to baseline in the Velvet Antler group and not placebo, although a lack of information on blinding and randomization precludes results that can be drawn from this study.