Male Osteoporosis: Causes, Diagnosis, and Evidence-Based Treatment

Why Men Get Osteoporosis

Male osteoporosis is widely underdiagnosed because clinicians and patients alike associate the disease almost exclusively with postmenopausal women. The reality: one in four men over age 50 will sustain an osteoporotic fracture in his remaining lifetime, according to data from the National Osteoporosis Foundation. That statistic rivals the lifetime risk of prostate cancer.

Men begin with larger, thicker bones and reach a higher peak bone mass than women, typically by age 25-30. Age-related bone loss in men proceeds more slowly (0.5-1% per year after age 50 compared to 2-3% per year in early postmenopausal women), yet the cumulative deficit still crosses the osteoporosis threshold for millions of men by their seventh and eighth decades [1]. The trabecular bone thinning pattern also differs: men tend to lose trabecular thickness while women lose entire trabeculae, which partly explains why men fracture later in life but with worse outcomes when they do [2].

A 2010 analysis published in the Journal of Bone and Mineral Research (N=5,880 men, MrOS cohort) confirmed that men with hip fractures had a one-year mortality rate of 37.5%, roughly double the rate observed in women. This mortality gap persists even after adjusting for age and comorbidities, likely because men present with fractures at older ages, have more comorbid illness at diagnosis, and receive less post-fracture osteoporosis treatment.

Secondary Causes Are the Rule, Not the Exception

Unlike postmenopausal osteoporosis, male osteoporosis has an identifiable secondary cause in up to 64% of cases. Targeted evaluation changes treatment. A workup should precede or accompany any prescription.

The Endocrine Society's 2012 clinical practice guideline recommends measuring serum testosterone, 25-hydroxyvitamin D, calcium, phosphorus, alkaline phosphatase, creatinine, CBC, TSH, and 24-hour urine calcium as a baseline panel. If clinical suspicion exists, add serum protein electrophoresis (to rule out multiple myeloma), celiac antibodies, and a 24-hour urine cortisol.

The most common secondary causes include:

Hypogonadism. Low testosterone contributes to roughly 20% of male osteoporosis cases. Both testosterone and its aromatized metabolite estradiol maintain bone density in men. The Framingham Osteoporosis Study showed that serum estradiol, not testosterone, was the stronger predictor of bone mineral density (BMD) at the hip in older men. This finding has implications for TRT: testosterone replacement alone may not fully correct bone loss if aromatization is impaired or if estradiol levels remain low.

Glucocorticoid use. Chronic corticosteroid therapy is the most common drug-induced cause of osteoporosis in both sexes. Bone loss begins within the first 3 months and is most rapid in the first 6-12 months. The American College of Rheumatology 2022 guideline recommends fracture risk assessment for any adult receiving prednisone 2.5 mg or more daily for 3 months or longer.

Alcohol excess. Consuming more than 3 units of alcohol per day doubles fracture risk independently of BMD, per WHO FRAX model data.

Androgen deprivation therapy (ADT). Men receiving ADT for prostate cancer lose 2-8% of BMD per year. A large cohort study (N=50,613) found that GnRH agonist therapy increased fracture risk by 21-54% depending on duration.

How to Screen and Diagnose

DEXA scanning of the hip and lumbar spine remains the gold standard. The ISCD (International Society for Clinical Densitometry) recommends DEXA for all men aged 70 and older, and for men aged 50-69 who have one or more risk factors: prior fragility fracture, glucocorticoid use, hypogonadism, excessive alcohol intake, smoking, low body weight (BMI <20), or a parent with hip fracture.

T-scores in men use a male reference database. The WHO diagnostic criteria apply the same thresholds: a T-score of -1.0 to -2.5 is osteopenia, and -2.5 or below is osteoporosis. The FRAX calculator (fractureriskassessment.org) estimates 10-year probability of major osteoporotic fracture. The National Osteoporosis Foundation guideline recommends pharmacologic treatment when FRAX shows 10-year hip fracture probability of 3% or greater, or major osteoporotic fracture probability of 20% or greater.

One diagnostic pitfall: vertebral fractures. Up to two-thirds of vertebral compression fractures are clinically silent. The MrOS study reported that men with incidental radiographic vertebral fractures had a 3.2-fold higher risk of subsequent clinical fracture. Vertebral fracture assessment (VFA) on the DEXA machine adds roughly 30 seconds to the scan and should be ordered for men aged 80 or older, or men aged 70-79 with a T-score of -1.5 or worse.

FDA-Approved Drug Therapies for Men

Several drugs carry FDA approval specifically for osteoporosis in men. Selection depends on fracture severity, secondary cause, and tolerability.

Alendronate (Fosamax). The key trial in men was a 2-year, placebo-controlled RCT (N=241) published in the New England Journal of Medicine. Alendronate 10 mg daily increased lumbar spine BMD by 7.1% versus 1.8% with placebo. Vertebral fracture incidence dropped by approximately 60%. Alendronate is dosed at 70 mg once weekly for convenience. It costs $4-15 per month as a generic.

Risedronate (Actonel). Approved for male osteoporosis based on a 1-year bridging study (N=284) showing BMD gains comparable to those in postmenopausal women. Dosed at 35 mg weekly or 150 mg monthly.

Zoledronic acid (Reclast). A single annual 5 mg IV infusion. The HORIZON Recurrent Fracture Trial (N=2,127, 24% male) demonstrated a 35% reduction in all clinical fractures and a 28% reduction in all-cause mortality over 1.9 years in patients who had sustained a recent hip fracture. This remains the only osteoporosis drug to show a mortality benefit in a randomized trial.

Denosumab (Prolia). A RANK ligand inhibitor given as 60 mg subcutaneous injection every 6 months. The ADAMO trial (N=242 men) showed a 5.7% increase in lumbar spine BMD at 12 months versus 0.9% with placebo. One critical consideration: discontinuing denosumab triggers a rapid rebound in bone resorption. The Endocrine Society warns that vertebral fractures may occur within 7-12 months of the last dose, so patients must transition to a bisphosphonate before or immediately after stopping denosumab.

Teriparatide (Forteo). The only anabolic agent with long-standing FDA approval for men. Dosed as 20 mcg subcutaneous injection daily for up to 24 months. A key trial in men (N=437) published in the Journal of Bone and Mineral Research showed a lumbar spine BMD increase of 5.9% at 11 months. Teriparatide is typically reserved for men with severe osteoporosis (T-score below -3.0), multiple vertebral fractures, or failure of antiresorptive therapy. Cost remains a barrier: approximately $3,400 per month without insurance, though biosimilar teriparatide products have brought this down significantly.

Abaloparatide (Tymlos). A PTHrP analog approved in 2017 for osteoporosis in men at high fracture risk. Dosed at 80 mcg subcutaneous injection daily.

Glucocorticoid-Induced Osteoporosis in Men

Steroid-induced bone loss deserves separate attention because it is the most preventable form of osteoporosis and follows a distinct pathophysiology. Glucocorticoids suppress osteoblast function (reducing bone formation) while simultaneously increasing osteoclast lifespan (accelerating bone resorption). They also reduce intestinal calcium absorption and increase renal calcium excretion.

The 2022 American College of Rheumatology guideline conditionally recommends oral bisphosphonates as first-line prophylaxis for adults aged 40 and older who are starting prednisone 2.5 mg or more daily for an anticipated duration of 3 months or longer and whose FRAX score exceeds a moderate threshold. For patients at high fracture risk (prior osteoporotic fracture or T-score below -2.5), the guideline conditionally recommends teriparatide or denosumab over oral bisphosphonates, citing superior BMD gains.

A head-to-head RCT (N=428) comparing teriparatide with alendronate in glucocorticoid-induced osteoporosis found that teriparatide produced significantly fewer new vertebral fractures (0.6% vs. 6.1%) over 36 months.

The Endocrine Society expert panel recommends reassessing fracture risk annually in patients on chronic glucocorticoids, because bone loss can accelerate with dose changes or new comorbidities.

Testosterone, Estradiol, and Bone: What TRT Does and Does Not Do

The relationship between male sex hormones and bone density is more nuanced than many clinicians recognize. As Dr. Benjamin Leder of Massachusetts General Hospital noted in a 2015 New England Journal of Medicine study (N=198): "Estrogen deficiency is the main cause of bone loss in older men when testosterone levels are below normal."

That study systematically suppressed endogenous sex steroids in healthy men aged 20-50 and selectively added back testosterone, estradiol, or both. Bone resorption markers increased only when estradiol fell below 10 pg/mL, regardless of testosterone concentration. The clinical takeaway: TRT protects bone primarily through aromatization to estradiol, and men who use aromatase inhibitors alongside TRT may lose that skeletal benefit.

For men with confirmed hypogonadism (total testosterone consistently below 300 ng/dL) and osteoporosis or osteopenia, the Endocrine Society 2018 testosterone guideline recommends testosterone replacement as part of the treatment plan, while noting that testosterone alone has not been proven to reduce fracture risk in randomized trials. If fracture risk is high, a bone-specific agent (bisphosphonate or denosumab) should be added to TRT rather than relying on TRT alone.

The Testosterone Trials (TTrials) bone sub-study (N=211 men aged 65 and older with low testosterone) found that 1 year of transdermal testosterone increased lumbar spine volumetric BMD by 7.5% and estimated bone strength by 10.8% on quantitative CT. These are meaningful gains, but the trial was not powered to detect fracture reduction.

Non-Pharmacologic Foundations

Drugs work best on a foundation of adequate calcium, vitamin D, and mechanical loading. These are not optional add-ons.

Calcium. The Institute of Medicine recommends 1,000 mg daily for men aged 51-70 and 1,200 mg daily for men over 70. Dietary sources first (dairy, fortified foods, sardines). Supplements should be calcium carbonate or citrate, taken in divided doses of 500 mg or less for optimal absorption.

Vitamin D. Target 25-hydroxyvitamin D of 30-50 ng/mL. The standard maintenance dose is 800-1,000 IU daily. Men found to be deficient (below 20 ng/mL) should receive a repletion protocol: 50,000 IU of ergocalciferol or cholecalciferol weekly for 8 weeks, then switch to maintenance dosing.

Exercise. A meta-analysis of 24 RCTs (N=1,313) found that resistance training and high-impact loading exercise significantly increased femoral neck BMD in older adults, with a weighted mean difference of 0.01 g/cm² versus controls. Clinically, this translates to slowing or halting age-related bone loss at the hip. The specific prescription: weight-bearing and resistance exercises 3-5 days per week, 30-60 minutes per session.

Fall prevention. Because fractures require both fragile bone and a mechanical event, reducing fall risk is as important as increasing BMD. Balance training, home hazard modification, vision correction, and medication review (especially sedatives and antihypertensives) each independently reduce fall incidence by 15-30% in older adults, per Cochrane review data.

Monitoring Treatment Response

After starting pharmacotherapy, repeat DEXA at 1-2 years. A stable or increasing BMD confirms response. A decline of more than 3-5% at the lumbar spine or more than 4-5% at the hip may indicate treatment failure, nonadherence, or an undiagnosed secondary cause.

Bone turnover markers (CTX for resorption, P1NP for formation) can confirm pharmacologic effect within 3-6 months and are particularly useful for verifying adherence to oral bisphosphonates. CTX should drop by 30% or more within 3 months of starting alendronate.

Men on teriparatide or abaloparatide should transition to an antiresorptive agent (bisphosphonate or denosumab) after completing the anabolic course, because BMD gains reverse within 12-18 months if no follow-on therapy is given, per findings from the DATA-Switch study.