Androgen Deprivation Therapy: What Happens Without Testosterone

Six months into treatment he told his oncologist he felt like a different person. Not worse in any way she could measure, and the PSA was down, which was the point. Different.

Hot flushes that woke him. Strength gone from his arms without the gym routine changing. A flatness he could not name.

She said that was expected. Nobody had told him beforehand what expected would feel like.

What this treatment does

Prostate cancer is usually driven by testosterone. Androgen deprivation therapy removes it.

The target is castrate level, generally defined as testosterone below 50 ng/dL, or about 1.7 nmol/L. For context, a healthy man sits somewhere between 300 and 900.

So this is not a reduction. It is near-total removal, achieved deliberately, and it works. ADT is one of the most effective treatments in oncology for a hormone-driven cancer.

Three main approaches:

GnRH agonists such as goserelin and leuprorelin, which overwhelm the signalling system until it shuts down. These cause a brief testosterone surge first, which is why an anti-androgen is often given alongside for the first weeks.

GnRH antagonists such as degarelix, which block the signal directly with no initial surge.

Anti-androgens such as bicalutamide, which block the receptor rather than lowering the hormone.

Why this article exists

Because ADT is the clearest natural experiment available on what testosterone actually does.

Everywhere else on this site, the evidence comes from men with moderately low levels, where effects are modest and confounded. Here testosterone goes to almost nothing, in a defined population, under supervision.

What happens next tells you more about testosterone's role than any observational study.

And the answers matter practically. Men on ADT are rarely told what to expect, and much of it is manageable if you know it is coming.

What removing testosterone does

Hot flushes. Around 80 per cent of men experience them, and they are frequently the most disruptive symptom day to day. Same mechanism as in women at menopause: withdrawal of sex hormones destabilises the brain's temperature control.

Muscle loss and fat gain. Lean mass falls and fat rises, particularly around the middle, and it happens quickly. This is the clearest demonstration that testosterone maintains body composition rather than merely building it.

Bone loss. This is the one with the hardest numbers. Bone mineral density falls by around 2 to 5 per cent in the first year, several times the rate of normal ageing, and fracture risk rises with duration of treatment.

Metabolic change. Insulin resistance develops, lipids shift, and the risk of type 2 diabetes increases. Much of this tracks the change in body composition. Testosterone and type 2 diabetes covers the same mechanism from the other direction.

Sexual function. Libido typically disappears rather than diminishes, and erectile function is usually lost. This is the effect men find hardest to raise and the one most often skipped in the consultation.

Fatigue and mood. Persistent tiredness is common, and rates of depression are higher on ADT. Some men describe emotional flattening distinct from low mood.

Cognition. Some studies show changes in verbal memory and processing speed, though the evidence is mixed and effect sizes small. Testosterone and your brain covers why this area is harder to read than it looks.

What this proves, and what it does not

Worth being careful here, because the temptation is to extrapolate.

It proves testosterone maintains muscle, bone and metabolic health. Remove it entirely and all three deteriorate measurably within a year. That is not an association; it is an intervention.

It proves testosterone drives libido. Near-total removal removes it in almost everyone.

It does not mean more testosterone produces more of any of these. The relationship is not linear. Going from castrate level to normal produces large changes; going from normal to high produces little, which is why testosterone therapy helps deficient men and does nothing for men with adequate levels.

That distinction is the single most misused idea in this field. High testosterone in men covers the other end.

What actually helps on ADT

This is the practical part, and the evidence is better than most men are told.

Resistance training. The best-evidenced intervention by a distance. Trials show it preserves lean mass, reduces fatigue, improves quality of life, and helps bone. Two or three sessions weekly, progressive. This is not general advice about exercise being good; it is specific, tested, and it works.

Bone protection. Baseline DEXA scan, calcium and vitamin D, and bisphosphonates or denosumab where risk is high. Given a 2 to 5 per cent annual loss, this should be routine and often is not. Ask if it has not been raised.

Hot flush management. Several options exist, including venlafaxine and other non-hormonal approaches. Worth asking about rather than enduring.

Cardiovascular and metabolic monitoring. Blood pressure, lipids, HbA1c. The metabolic changes are predictable, which makes them checkable.

Psychological support. Higher rates of depression are documented, and this is a treatment that changes how men experience themselves. Support is appropriate rather than excessive.

Intermittent versus continuous

For some men with certain disease patterns, ADT can be given intermittently, with breaks once PSA falls.

Testosterone recovers partially during breaks, and quality of life improves. Trials suggest outcomes are comparable to continuous treatment in selected patients.

Whether it suits you depends on your disease stage and characteristics, and it is a decision for your oncology team. But it is worth knowing the option exists, because it is not always offered.

When treatment stops

Recovery is possible and slow. Testosterone returns over months to years after stopping, and recovery is less complete in older men and after longer treatment.

Some men never return to baseline, and testosterone replacement after prostate cancer is a specialist discussion rather than a straightforward one. The old absolute prohibition has softened considerably, but it remains a conversation for a urologist who knows your case. Does testosterone cause prostate cancer? covers how that evidence has shifted.

The honest summary

Androgen deprivation therapy works, and the side effects are the price of that.

What makes them harder than necessary is that men are rarely told in advance what to expect, and rarely told that resistance training and bone protection genuinely change how the next few years go.

If you are starting ADT, two questions are worth asking before the first injection: what is being done about my bones, and can I be referred for supervised exercise?

Both have evidence behind them. Neither is routine. Both should be.

Common questions

What is androgen deprivation therapy?

Treatment that lowers testosterone to castrate level, below about 50 ng/dL, to slow hormone-driven prostate cancer. Delivered as GnRH agonists, GnRH antagonists or anti-androgens.

What are the main side effects?

Hot flushes in around 80 per cent, muscle loss, fat gain, bone loss of 2 to 5 per cent in the first year, insulin resistance, loss of libido and erectile function, fatigue, and higher rates of depression.

Can anything reduce them?

Resistance training has the strongest evidence, preserving lean mass and reducing fatigue. Bone protection with calcium, vitamin D and sometimes bisphosphonates is important given the rate of loss. Hot flushes respond to several non-hormonal treatments.

Will my testosterone come back?

Usually, over months to years after stopping, though recovery is less complete in older men and after longer treatment. Some men do not return to baseline.

Does this prove testosterone is essential?

It proves testosterone maintains muscle, bone, metabolic health and libido, since removing it degrades all four. It does not mean higher testosterone improves them further; the relationship is not linear.

What is intermittent ADT?

Treatment given in cycles with breaks once PSA falls, allowing partial testosterone recovery. Suitable for some disease patterns and associated with better quality of life. Worth asking whether it applies to you.

Can I take testosterone after prostate cancer?

Possibly, but it is a specialist decision. The absolute prohibition has softened as evidence has changed, though it remains a discussion for a urologist familiar with your case.

Sources: Mottet N et al., EAU-EANM-ESTRO-ESUR-SIOG guidelines on prostate cancer · Greenspan SL et al., Bone loss after initiation of androgen deprivation therapy in patients with prostate cancer, J Clin Endocrinol Metab 2005;90(12):6410-7 · Galvão DA et al., Combined resistance and aerobic exercise programme reverses muscle loss in men undergoing androgen suppression therapy, J Clin Oncol 2010;28(2):340-7 · Nguyen PL et al., Adverse effects of androgen deprivation therapy and strategies to mitigate them, Eur Urol 2015;67(5):825-36 · Educational only, not medical advice. Never change cancer treatment without speaking to your oncology team.

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