Other significant adverse effects of testosterone supplementation include acceleration of pre-existing prostate cancer growth in individuals who have undergone androgen deprivation; increased hematocrit , which can require venipuncture in order to treat; and, exacerbation of sleep apnea .  Adverse effects may also include minor side-effects such as acne and oily skin, as well as, significant hair loss and/or thinning of the hair, which may be prevented with 5-alpha reductase inhibitors ordinarily used for the treatment of benign prostatic hyperplasia , such as finasteride .  Exogenous testosterone may also cause suppression of spermatogenesis , leading to, in some cases, infertility.  It is recommended that physicians screen for prostate cancer with a digital rectal exam and prostate-specific antigen (PSA) level before starting therapy, and monitor PSA and hematocrit levels closely during therapy. 
Drugs can be added and removed from this list by WADA annually, although not all of the banned substances are explicitly named. Caroline Hatton, PhD , a sports anti-doping science consultant, told in a Mar. 12, 2010 email that "A key concept in prohibited lists is that they avoid being finite. Instead of listing all banned drugs one by one, they list entire drug classes and name drugs merely as examples. This is to keep users who took designer drugs from claiming that they didn't break the rules because the drugs they took weren't listed."