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. 
Here’s the lowdown. The practice of your GP (and indeed endocrinologist) should be in line with very detailed guidelines available. When the testosterone is indicated and prescribed by your GP then you will pay privately for the script. For the majority of men who are non concession-card holders, the injections will be around the same price they were before. The price of topical therapy will however be considerably more expensive. Clearly, men who require treatment are likely to opt for private scripts for injections from their doctor which is cost-effective, or be referred for consideration of topical testosterone.