Most side effects are dose related.  The following list is not exhaustive, but these adverse events have been reported:

Common side effects-

• Acne and excessive facial oiliness.

• Facial hair growth in women (hirsutism). Scalp hair loss in both men and women.

• Irritability, mood changes, and insomnia.

Serious side effects-

• Heart irregularities

• Possible stimulation of hormone-sensitive cancers (prostate, breast, ovarian, uterine).

Of the effects listed, the stimulation of hormone-sensitive cancers seems to the be the most worrisome throughout the literature.  Some in vitro studies have shown that DHEA can actually produce proliferation of breast cancer cells (10).  As such, it is generally advised that patients with breast and other hormone-sensitive cancers avoid DHEA supplementation.  

Note:  No studies have been conducted on the long-term safety of DHEA.  DHEA is not recommended for people under age 40, unless DHEA levels are known to be low (less than 130 mg/dL in women and less than 180 mg/dL in men).  People taking DHEA should have their blood levels monitored every 6 months.