ADT, or androgen deprivation therapy, is a treatment for prostate cancer that works by drastically lowering testosterone levels or blocking testosterone from fueling cancer cell growth. It’s one of the most widely used treatments for advanced prostate cancer, and it remains a cornerstone of management for men whose cancer has spread beyond the prostate or returned after initial treatment.
How ADT Works
Prostate cancer cells depend on androgens, primarily testosterone, to grow and multiply. About 90% of testosterone is produced in the testes, with the remaining fraction coming from the adrenal glands. Once produced, testosterone converts into a more potent form called DHT, which binds to receptors on prostate cancer cells and signals them to keep growing. ADT interrupts this process by either shutting down testosterone production or physically blocking testosterone from reaching those receptors.
The goal is to bring blood testosterone below 50 ng/dL, a threshold known as “castrate level.” Normal testosterone in adult men typically ranges from 300 to 1,000 ng/dL, so ADT represents a dramatic reduction. Some researchers have argued that a stricter target of below 20 ng/dL produces better outcomes, but 50 ng/dL remains the standard clinical benchmark.
Types of ADT
There are several ways to achieve androgen deprivation, and the right choice depends on a person’s cancer stage, overall health, and preferences.
Hormone-Releasing Hormone Agonists
These are the most commonly prescribed form of ADT. They work through an indirect mechanism: by continuously stimulating the brain’s hormone signaling system, they eventually overwhelm and shut it down, causing the pituitary gland to stop telling the testes to make testosterone. The catch is that during the first one to three weeks, testosterone actually surges before it drops. This “flare” can temporarily worsen symptoms, particularly bone pain in men with cancer that has spread to the skeleton. Pain from flare typically peaks around 36 hours after the first dose and fades by the end of the first week. To prevent this, doctors prescribe an anti-androgen medication to block testosterone’s effects during that initial window. Castrate testosterone levels are usually reached by three weeks.
Hormone-Releasing Hormone Antagonists
These newer drugs work by directly blocking hormone receptors in the pituitary gland, producing an immediate drop in testosterone without any flare. This makes them particularly useful for men who have cancer compressing the spinal cord or other situations where even a brief testosterone spike could be dangerous. Antagonists also appear to carry a significantly lower cardiovascular risk. In clinical studies, men on antagonists had roughly half the rate of major heart events compared to men on agonists.
Surgical Removal of the Testes
Bilateral orchiectomy, the surgical removal of both testes, is the oldest form of ADT and achieves permanent castrate testosterone levels within hours. It costs less over time, eliminates the need for ongoing injections, and removes any risk of missed doses. Survival outcomes are equivalent to drug-based ADT, with no measurable difference in a study of nearly 42,000 men followed for a median of 30 months. Despite its effectiveness, most men opt for medication because the surgery is irreversible and carries significant psychological weight.
Anti-Androgens and Androgen Synthesis Blockers
Anti-androgens don’t lower testosterone levels. Instead, they block the androgen receptor directly, preventing testosterone and DHT from activating cancer cells. They’re often used in combination with other forms of ADT. A separate class of drugs blocks an enzyme involved in androgen production in both the adrenal glands and within tumors themselves, targeting the small but meaningful amount of testosterone produced outside the testes.
Continuous vs. Intermittent Treatment
ADT can be given continuously or in cycles. With intermittent therapy, a man receives ADT for several months until his PSA drops to a low level, then pauses treatment. If PSA rises again, treatment restarts. A large trial published in the New England Journal of Medicine compared the two approaches in men with metastatic prostate cancer and found that intermittent therapy offered small improvements in quality of life, including better erectile function and mental health during the first few months off treatment. Survival outcomes were similar enough that intermittent therapy is considered a reasonable option for many men, particularly those who struggle with side effects.
Metabolic and Body Composition Changes
Testosterone does far more than drive prostate cancer. It plays a major role in muscle maintenance, fat distribution, bone density, and metabolism. Removing it from the equation causes body-wide changes that begin within months.
In prospective studies, men starting ADT gained 1.8 to 3.1% of their body weight while losing 2.7 to 3.8% of their lean muscle mass. Body fat increased by 9.4 to 11.2%. These shifts happen even without changes in diet or exercise, though staying active can help limit them.
ADT also disrupts how the body processes sugar and fat. Within just 12 weeks, fasting insulin levels rise by about 26%, and the body’s sensitivity to insulin drops by roughly 11 to 13%. Cholesterol shifts too: total cholesterol climbs by up to 10.6%, triglycerides by more than 25%, and LDL (the harmful type) by about 7% over a year. These changes collectively push men toward a higher risk of developing diabetes and metabolic syndrome.
Bone Loss
One of the most clinically significant side effects is rapid bone thinning. In the first year of ADT, men lose bone density at 5 to 10 times the rate of healthy men the same age. Specific measurements show losses of 4% at the spine, 2.5% at the hip, and 3.3% across the total body within 12 months. Bone loss is steepest during that first year, which is why preventive measures, including weight-bearing exercise, calcium, vitamin D, and sometimes bone-protecting medications, are typically started early rather than waiting for a fracture to occur.
Cardiovascular Risks
The relationship between ADT and heart health has become one of the most studied aspects of this therapy. Men on hormone-releasing agonists have a 16% higher risk of coronary heart disease and an 11% higher risk of heart attack compared to men not on ADT, based on large observational data. The risk of sudden cardiac death rises by 34%.
The type of ADT matters considerably. In one study, 20% of men on agonists experienced a significant cardiovascular or cerebrovascular event compared to just 3% of those on antagonists. Across multiple analyses, antagonists consistently show roughly a 50% lower risk of cardiovascular complications. For men who already have heart disease or significant cardiovascular risk factors, this difference often influences which drug their oncologist recommends. Surgical castration also carries cardiovascular risks, particularly in older men and those with pre-existing heart conditions.
Monitoring During Treatment
PSA blood tests are the primary tool for tracking how well ADT is working. Guidelines recommend checking PSA every 6 to 12 months for the first five years, then annually after that. A rising PSA while on ADT is often the first sign that the cancer is becoming resistant to hormone therapy, a condition called castration-resistant prostate cancer. At that point, treatment strategies shift to more aggressive options.
Beyond PSA, men on ADT are typically monitored for the metabolic and bone complications described above. This includes periodic bone density scans, blood sugar and cholesterol panels, and cardiovascular risk assessments. The side effects of ADT are manageable, but only if they’re tracked and addressed proactively rather than discovered after damage has accumulated.