Is a DEXA (Dual-Energy X-ray Absorptiometry) scan appropriate for a patient over 50 with risk factors for osteoporosis who is on testosterone replacement therapy?

DEXA Scan for Testosterone Replacement Therapy

Yes, DEXA scanning is appropriate and recommended for patients over 50 on testosterone replacement therapy, as hypogonadism is an established risk factor for secondary osteoporosis that warrants bone mineral density assessment. 1

Primary Rationale for Screening

The American College of Radiology explicitly identifies hypogonadal men older than 18 years and men with surgically or chemotherapeutically induced castration as candidates requiring DEXA evaluation. 1 This recommendation applies regardless of whether testosterone replacement has been initiated, as:

• Testosterone deficiency syndrome increases risk of low BMD and osteoporosis, with studies showing 83% of hypogonadal men have lumbar osteopenia/osteoporosis and 61% have femoral osteopenia/osteoporosis at initial assessment. 2
• Men over 50 with hypogonadism should undergo DXA scanning to stratify fracture risk and guide treatment decisions. 3
• Testosterone replacement therapy has only limited osteoanabolic effects, maintaining bone density but not fully reversing pre-existing deficits—61% of patients remain osteopenic/osteoporotic even after years of continuous TRT. 2

Timing and Baseline Assessment

Obtain baseline DEXA of lumbar spine and bilateral hips before or shortly after initiating testosterone replacement therapy. 1 The ACR guidelines rate this as "usually appropriate" (rating 9/9) for men with risk factors including hypogonadism. 1

For men already on TRT without prior bone density assessment:

• Order DEXA immediately if the patient is over 50 years old, as this age threshold combined with hypogonadism creates sufficient risk regardless of treatment duration. 4
• Do not delay screening based on duration of testosterone therapy—bone loss may have occurred before treatment initiation and TRT provides only modest improvement. 2

Follow-Up Monitoring Schedule

The monitoring interval depends on initial findings:

• If osteoporosis is present (T-score ≤ -2.5): Repeat DEXA every 1-2 years to monitor treatment response. 4
• If osteopenia is present (T-score -1.0 to -2.5): Repeat DEXA every 2-3 years. 4
• If bone density is normal: Repeat DEXA every 2-5 years given the ongoing risk from prior hypogonadism. 4

The ACR recommends 2-year intervals as standard for monitoring patients with risk factors for substantial bone loss. 1

Interpretation Considerations

Use Z-scores (not T-scores) for men under 50 years of age, as WHO criteria for osteoporosis do not apply to this population. 1 Z-scores of -2.0 or less are defined as "below the expected range for age." 1

For men 50 years and older, T-scores are appropriate and standard WHO diagnostic criteria apply (T-score ≤ -2.5 indicates osteoporosis). 1

Critical Pitfalls to Avoid

• Do not assume testosterone replacement adequately protects bone health—BMD remains in the osteopenic/osteoporotic range in most hypogonadal patients despite continuous TRT, and bone density clearly decreases if treatment is interrupted. 2
• Do not wait until age 70 to initiate screening as recommended for the general male population—hypogonadism requiring TRT is itself an indication for earlier assessment. 1, 4
• Do not rely solely on lumbar spine measurements if degenerative changes are present—spuriously elevated readings from spondylosis can mask true osteoporosis, requiring hip or forearm assessment instead. 1
• Do not forget to assess for additional risk factors including glucocorticoid use, chronic inflammatory conditions, malabsorption, vitamin D deficiency, or prior fragility fractures, which may warrant more aggressive monitoring or treatment. 1

Treatment Implications

Men with TDS and confirmed osteoporosis should receive anti-osteoporotic agents in addition to testosterone replacement therapy. 3 TRT alone has beneficial but limited effects on BMD, and combination therapy is necessary for optimal fracture risk reduction. 2, 3

Men with osteopenia should be stratified by fracture risk using FRAX or similar tools—those at high risk warrant anti-osteoporotic agents plus TRT, while those at low risk should receive TRT with close monitoring. 3