A lot of you have reached out asking me to help you actually understand bone health, so I’m going to talk you through it, plain and simple, just like I would in the office. And here’s the thing: this one is for more people than you’d expect. It’s for:

Watch the 12-minute whiteboard explainer:

As a urologist, I watch men start androgen deprivation therapy focused entirely on the cancer, as they should be. What I also stress to patients is that it also impacts their bones.

The number that should catch grab your attention: by year 10 on ADT, roughly 81% of men have osteoporosis which increases the risk of a fracture. And a broken hip in your 80s is not a minor setback; it is one of the most dangerous events in medicine.

The good news is that this is one of the most preventable complications. The interventions are cheap, most are free, and the sequence matters. Let me walk you through it.

Bone is not static, it is constantly torn down and rebuilt.

A normal older man loses 0.5 to 1% of bone density per year. On ADT, that jumps to 3 to 5% per year, roughly 3 to 10 times faster than normal aging. Stay on it long enough and the math is brutal: about 81% of men are osteoporotic by year 10.

This isn’t a slow drift. Most of the damage lands early, in the first 12 months.

Here’s the part that surprises most men: the hormone protecting your bones was never really testosterone. It was estrogen.

In men, an enzyme called aromatase converts a portion of testosterone into estrogen. That estrogen is the brake on your osteoclasts, the cells that break bone down. ADT removes testosterone, but in doing so it also removes the estrogen your bones depended on. Without estrogen, the brake comes off the osteoclasts. As a result, the bone is broken down faster than it can be rebuilt and bone density falls.

You spend your whole life told testosterone is the male hormone. For your bones, the one that actually mattered was the estrogen which men were quietly making from testosterone.

This single fact, that estrogen, not testosterone, guards the skeleton, is why one of the most interesting alternatives to standard ADT is estrogen itself. More on that below.

Bone loss on ADT isn’t uniform. In the first year, the typical declines are:

Why care about a few percentage points? Because of how the risk scales. Every 10% drop in bone density roughly doubles the fracture risk at that site. A 3% loss increases risk about 20%, a 5% loss about 30%, and a 10% loss about 2-fold. Small numbers on a DEXA report translate into real fractures.

It’s easy to think of a fracture as a bad few months in a cast. A hip fracture in an older man is something else entirely.

A hip fracture at 80 carries a one-year mortality of 14 to 30%. Breaking it down: 6 to 10% of men die within 30 days, 13.5% by 6 months, and 14 to 30% within a year. Five-year survival after a hip fracture in men is about 38%. And the excess risk of death doesn’t fade quickly, it persists for more than 10 years.

Think of bone protection as a house. Drugs are not the foundation, they’re closer to the roof. Foundation first, drugs last.

Start with movement, and be specific, because walking alone is not enough. The combination that actually protects bone is:

In one trial, resistance plus impact training together produced about 50% less spine bone loss (Newton 2019).

And if you smoke, this is the moment: smoking raises hip fracture risk by about 78%. Quitting is one of the highest-yield things you can do for your skeleton.

Calcium: aim for 1,000 to 1,200 mg total per day, food first. Milk, yogurt, and leafy greens should do most of the work. Here’s the nuance most people miss: supplemental calcium at 1,000 mg/day or more has been linked to a 14 to 24% higher risk of heart attack. Dietary calcium did not increase the risk of heart attack. So supplement only the amount that you cannot get from diet.

Vitamin D3: 2,000 to 3,000 IU/day, targeting a blood level of 40 to 60 ng/mL. Adequate vitamin D is associated with about an 11% lower hip fracture risk (HR 0.89, Wallace meta-analysis). Think of it as a complement to exercise.

Vitamin K (as K2, MK-7) gets marketed hard for bone. The honest read: the effect is small and shaky.

K2 produces about a 1 to 2% gain in lumbar-spine bone density over 3 years, real, but modest. More importantly, its apparent effect on actual fractures disappears once you look only at low-bias trials (Mott 2019). It’s optional, and no substitute for anything above.

Not every man on ADT needs a medication to strengthen their bones on day one. The tool that decides is FRAX, a free calculator that estimates your 10-year fracture risk from your age, weight, family history, smoking, DEXA T-score, and yes, ADT itself.

FRAX gives you two numbers: a 10-year hip fracture risk and a 10-year major osteoporotic fracture risk. A hip risk of 4%, for example, means about 4 of every 100 men will break a hip in the next decade.

The thresholds that should trigger a medication conversation:

Print your FRAX from your DEXA report, or run it free in about 2 minutes. If you cross either line, it’s time to talk about a drug.

If you need medication, there are three well-established options. All of them work; they differ in convenience, cost, and caveats.

Denosumab (injection every 6 months). The strongest fracture data of the three, fracture risk down about 62% in men on ADT, plus the largest bone density gains and no pills to remember. It’s fine in chronic kidney disease stages 1 to 3. The catches: it cannot be given to people if their kidney function is very low (CrCl under 30, because of hypocalcemia risk), it needs daily calcium and vitamin D indefinitely, and, most important, stopping it without bridging to a bisphosphonate can trigger a wave of rebound fractures. Plan to stay on it, or bridge off it deliberately.

Zoledronic acid (a one-hour IV infusion, once a year). Bone density gains about equal to denosumab, but with two advantages: a drug holiday is safe, and there is no rebound when you stop. The main downside is a flu-like reaction after the first infusion, in about 25 to 30% of patients.

Alendronate (an oral pill, once a week). The cheapest option, with decades of safety data and a safe drug holiday. The trade-offs: 20 to 30% of people get heartburn or GI upset, the bone density gain is slightly smaller, and the morning ritual is strict, a full glass of water, an empty stomach, and staying upright for 30 minutes.

The short version: denosumab has the strongest fracture data (but you must stay on it or bridge off it), zoledronic acid is the once-a-year, holiday-friendly option, and alendronate is the cheap, proven workhorse if you can tolerate the routine.

Here’s where the biology comes full circle. If estrogen is the hormone your bones actually miss on ADT, what if the ADT itself were delivered as estrogen?

That’s the idea behind the transdermal estradiol (tE2) patch, tested head-to-head against standard LHRH-injection ADT in the PATCH trial (New England Journal of Medicine 2026; Langley et al., n=1,360). The results are striking:

Read that bone row again. Standard ADT lost 3% of spine density in two years; the patch gained nearly 8%. And the 10-year fracture rate was roughly halved, all while controlling the cancer at least as well.

The trade-off is real: the patch causes far more breast enlargement (37% vs 9%). That’s manageable, but it takes planning. A single prophylactic radiation dose, a 10 Gy electron beam, given before you start, can help, and bicalutamide roughly halves breast enlargement in other settings (52% vs 85%, Tyrrell 2004). One honest caution from PATCH itself: prophylactic radiation did not reduce breast enlargement in men on the estradiol patch, 42% with irradiation versus 41% without.

This is a conversation that belongs between you and your oncologist. But it’s one worth having, because for the skeleton, estrogen isn’t the risk. It’s the point.

Two safety rules prevent most of the trouble I see.

Get dental clearance before starting any bone drug. Denosumab and bisphosphonates are linked to jaw problems, and the time to handle a bad tooth is before you start, not after.

Once you start denosumab, don’t stop it cold. Stopping without bridging to a bisphosphonate can trigger a wave of rebound fractures. And because denosumab can lower your calcium, low calcium is an outright contraindication, hit that 1,000 to 1,200 mg total daily target (food first, never above 1,200) before and during treatment.

You may have a father, husband, brother on hormone therapy for prostate cancer or sister or mother with osteoporosis. Please share this. It’s the kind of information that turns a preventable hip fracture into a conversation with his doctor instead.