Androgen deprivation therapy, or ADT, is a treatment for prostate cancer that works by lowering testosterone to extremely low levels or blocking it from reaching cancer cells. Prostate cancer cells need testosterone to grow, so cutting off this fuel supply causes them to die or grow much more slowly. ADT is one of the most widely used treatments for advanced prostate cancer and often serves as the backbone of treatment plans that may include radiation, chemotherapy, or newer targeted drugs.
How ADT Works in the Body
Testosterone and a related hormone called DHT drive the growth of both normal and cancerous prostate cells. These hormones attach to a receptor inside prostate cells, which then switches on genes that tell the cells to multiply. ADT interrupts this process at different points depending on the type of therapy used. Some forms stop testosterone from being produced in the first place. Others block it from binding to that receptor, essentially locking the door so the hormone can’t get in.
The goal is to push testosterone down to what doctors call “castrate levels,” generally below 20 ng/dL. For comparison, normal testosterone in adult men typically ranges from 300 to 1,000 ng/dL. At these extremely low levels, most prostate cancer cells can no longer sustain their growth.
Types of ADT
ADT comes in several forms, and the differences matter for how you take the treatment, how quickly it works, and what side effects to expect.
Injections That Shut Down Testosterone Production
The most common approach uses drugs that signal the brain to stop telling the testes to produce testosterone. These are given as injections, typically every one to three months. One important caveat: when first injected, these drugs cause a temporary surge in testosterone before levels drop. This “testosterone flare” can briefly worsen symptoms, so doctors sometimes prescribe a short course of a blocking drug to counteract it.
Oral ADT
A newer option is a daily pill that suppresses testosterone without causing that initial surge. In the large HERO clinical trial, this oral approach achieved castrate-level testosterone in 96.7% of patients, compared to 88.8% for the traditional injectable form. Compliance was not a significant concern: 99% of patients in the trial took the pill as directed.
Surgical Option
Removing the testes surgically is the oldest form of ADT. It permanently eliminates the body’s main source of testosterone in a single procedure. While effective and low-cost, most men today prefer drug-based options because they’re reversible and feel less drastic.
When ADT Is Used
ADT is not typically a first-line treatment for early, low-risk prostate cancer. It becomes central to treatment at more advanced stages. Current guidelines strongly recommend ADT for men with metastatic prostate cancer that still responds to hormone therapy, often combined with additional treatments to improve outcomes. It’s also used alongside radiation therapy for intermediate and high-risk localized disease, where it can significantly improve the chances that radiation eliminates the cancer.
When prostate cancer stops responding to initial ADT (a stage called castration-resistant disease), testosterone suppression is still continued. Additional therapies are layered on top, including newer hormone-blocking drugs, chemotherapy, immunotherapy, or targeted treatments depending on the specifics of the cancer.
Continuous vs. Intermittent Treatment
Because ADT’s side effects can be significant, researchers have studied whether cycling on and off treatment (intermittent ADT) works as well as staying on it continuously. A large meta-analysis of 15 clinical trials involving nearly 7,000 patients found no meaningful difference in overall survival, cancer-specific survival, or time before the disease progressed between the two approaches.
Intermittent therapy did show improvements in physical and sexual functioning during the off-treatment periods, which matters a great deal for daily quality of life. For men with recurrent or metastatic prostate cancer, intermittent ADT is now considered a reasonable alternative to continuous treatment, though the decision depends on individual risk factors and should be tailored to each case.
Side Effects and Health Risks
Testosterone does far more than drive prostate cancer. It helps maintain muscle mass, bone density, red blood cell production, sexual function, and metabolic health. Suppressing it has wide-ranging consequences.
The most common side effects include fatigue, hot flashes, loss of sex drive, erectile dysfunction, breast tissue growth, and weight gain. These aren’t subtle changes. Prospective studies tracking men on ADT found body fat increased by 9 to 11% while lean muscle mass dropped by roughly 3 to 4%, and overall weight climbed by about 2 to 3%. This shift in body composition, sometimes called sarcopenic obesity (losing muscle while gaining fat), sets the stage for broader metabolic problems.
Insulin sensitivity drops measurably within months. One study of men without diabetes found that fasting insulin levels jumped nearly 26% after just 12 weeks of ADT, while the body’s ability to respond to insulin fell by 11 to 13%. These changes increase the risk of developing type 2 diabetes over time.
Bone and Heart Health
ADT accelerates bone loss, raising the risk of osteoporosis and fractures. This is particularly concerning because treatment may last years. Men on long-term ADT are often monitored with bone density scans and may take medications or supplements to protect their bones.
Cardiovascular risk is the other major concern. Multiple large studies have linked ADT to increased rates of heart attack, stroke, high blood pressure, and dangerous heart rhythm problems. One landmark study found that the traditional injectable form of ADT was associated with a 44% higher incidence of diabetes, a 16% increase in coronary heart disease, and a 16% increase in sudden cardiac death. A 2015 study confirmed a roughly 21% increased risk of cardiovascular disease overall. Men with pre-existing heart conditions need especially careful monitoring.
How Long ADT Keeps Working
ADT is effective at controlling prostate cancer, but it doesn’t work forever. Eventually, cancer cells find ways to grow without normal testosterone levels, a transition called castration resistance. How quickly this happens varies enormously based on how advanced the cancer was at diagnosis.
For men diagnosed without metastatic disease, the median time before the cancer becomes resistant is roughly 11 to 12 years. That’s a long window of disease control. But for men who already had cancer spread at diagnosis, the picture is very different: the median time to castration resistance was only about 27 months. Men with the highest-risk features (very high PSA levels, aggressive tumor grades, and metastatic disease at diagnosis) saw resistance develop in a median of roughly 20 months.
Castration resistance doesn’t mean treatment stops. It means the treatment strategy shifts. ADT continues as a foundation while additional drugs are added. Newer hormone-blocking agents have extended survival significantly for men with castration-resistant disease, and the combination of ADT with these drugs earlier in treatment is now standard practice for metastatic cases.
Living With ADT
The physical changes from ADT are real and can be managed but not entirely avoided. Regular exercise, particularly resistance training, helps counteract muscle loss and metabolic changes. Weight-bearing exercise also supports bone health. Many cancer centers now offer exercise programs specifically designed for men on ADT.
The emotional and psychological effects deserve equal attention. Fatigue, mood changes, and the loss of sexual function can significantly affect relationships and mental health. These aren’t minor quality-of-life footnotes. For many men, they’re the hardest part of treatment. Support groups, counseling, and open conversations with a care team can make a meaningful difference in navigating these changes over months or years of therapy.