Erectile dysfunction is not uncommon after radical prostatectomy and men who undergo ADT in addition to this are likely to show further decline in their ability to engage in penetrative intercourse, as well as their desire to do so.  A study looking at the differences of using GnRH-A (and androgen suppressant) or an orchiectomy report differences in sexual interest, the experience of erections, and the prevalence of participating in sexual activity. Men reporting no sexual interest increased from % to % after orchiectomy, and from % to % after GnRH-A; men who experienced no erections increased from % to %; and men who did not report engaging in sexual activity increased from % to % after orchiectomy and % to %.  This study suggests that the GnRH-A and orchiectomy had similar effects on sexual functioning. A vicious cycle whereby lowering testosterone levels leads to decreased sexual activity, which in turn cause both free and total testosterone levels to decline even further.  This demonstrates the importance of androgens for maintaining sexual structures and functions.  
Side effects of hormonal therapy will depend mainly on the type of hormonal therapy, the dose of a drug or combination of drugs, if any other treatments are given and your overall health. Some common side effects of hormonal therapy for prostate cancer are:
AB - ASCO provisional clinical opinions (PCOs) offer direction to the ASCO membership after publication or presentation of potential practice-changing data. This PCO addresses second-line hormonal therapy for chemotherapy-näive men with castration-resistant prostate cancer (CRPC) who range from being asymptomatic with only biochemical evidence of CRPC to having documented metastases but minimal symptoms. Clinical Context The treatment goal for CRPC is palliation. Despite resistance to initial androgen deprivation therapy, most men respond to second-line hormonal therapies. However, guidelines have neither addressed second-line hormonal therapy for nonmetastatic CRPC nor provided specific guidance with regard to the chemotherapy-näive population. Recent Data Six phase III randomized controlled trials and expert consensus opinion inform this PCO. Provisional Clinical Opinion For men with CRPC, a castrate state should be maintained indefinitely. Second-line hormonal therapy (eg, antiandrogens, CYP17 inhibitors) may be considered in patients with nonmetastatic CRPC at high risk for metastatic disease (rapid prostate-specific antigen doubling time or velocity) but otherwise is not suggested. In patients with radiographic evidence of metastases and minimal symptoms, enzalutamide or abiraterone plus prednisone should be offered after discussion with patients about potential harms, benefits, costs, and patient preferences. Radium-223 and sipuleucel-T also are options. No evidence provides guidance about the optimal order of hormonal therapies for CRPC beyond second-line treatment. Prostate-specific antigen testing every 4 to 6 months is reasonable for men without metastases. Routine radiographic restaging generally is not suggested but can be considered for patients at risk for metastases or who exhibit symptoms or other evidence of progression. Additional information is available at /genitourinary-cancer-guidelines and /guidelineswiki.