As alluded to above, one very important thing to acknowledge when using AAS (whether taking one hormone, stacking or cycling) is the risk of harmful side effects. Within a steroid cycle, the users will often stack other non-anabolic hormones into their program to maximize specific cycle objectives for example: the addition of drugs like Clenbuterol and/or Cytomel /T3 augment cutting/definition cycles; others called aromatase inhibitors (estrogen reducing drugs) like Letrozole . Letro and Anastrozole Arimidex are often included to inhibit the conversion of excess testosterone to negatively cycle impacting estrogen and; incorporating post-cycle therapy (PCT) drugs such as the synthetic estrogens Tamoxifen . Nolvadex , or Clomiphene Citrate . Clomid (which act as anti-estrogens in the male body), can be used alone, together, or in conjunction with those like Mesterolone . Proviron and Human Chorionic Gonadotropin ( HCG ) during PCT to bridge the gap between the end of a steroid cycle (synthetic testosterone usage) and the restoration of the bodys natural testosterone production. These drugs too must be researched, and controlled in similar fashion to AAS. Thus, steroid cycles can be as simple or complex as the users individualized goals, cycle histories and levels of understanding. Below are three samples of AAS stacked cycles of varying complexity along with a beginning PCT sample, and an explanation of goal intention & rationale for the selected compounds, dosages & durations. These illustrations and commentaries will provide a better understanding of what stacking and cycling are along with the many nuances they require.
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.