Why is this an endocrine issue?

Prostate cancer is often treated with Androgen Deprivation Therapy (ADT), which suppresses testosterone to slow cancer growth. However, testosterone is essential for bone health. ADT causes rapid bone loss, leading to osteoporosis and fractures—a serious side effect requiring endocrine management.

What is Androgen Deprivation Therapy (ADT)?

ADT lowers testosterone levels to castrate levels (<50 ng/dL) to slow or stop growth of testosterone-sensitive prostate cancer.

Common ADT Medications:

• GnRH Agonists: Leuprolide (Lupron®), Goserelin (Zoladex®), Triptorelin (Trelstar®)
• GnRH Antagonist: Degarelix (Firmagon®), Relugolix (Orgovyx®)
• Bilateral Orchiectomy: Surgical removal of testicles

How does ADT affect bones?

• Testosterone is protective for bone density in men
• ADT causes rapid bone loss—up to 2-8% per year (especially in first year)
• Increases fracture risk by 20-40%
• Hip and spine fractures are most common and debilitating

Other Side Effects of ADT:

• Hot flashes, night sweats
• Loss of libido, erectile dysfunction
• Fatigue, depression, mood changes
• Loss of muscle mass, increased body fat (especially abdominal)
• Gynecomastia (breast enlargement)
• Metabolic syndrome (weight gain, diabetes, dyslipidemia)
• Cardiovascular disease risk
• Cognitive changes ("chemo brain")

Screening and Monitoring for Bone Loss:

Baseline (Before Starting ADT):

• DEXA Scan: Measure baseline bone density (hip and spine)
• Labs: Calcium, Vitamin D (25-OH Vitamin D), testosterone

Follow-Up:

• DEXA scan every 1-2 years while on ADT
• Monitor Vitamin D, calcium, testosterone levels
• Assess fracture risk using FRAX calculator

Prevention and Treatment of Bone Loss:

1. Calcium and Vitamin D Supplementation:

• Calcium: 1200 mg/day (dietary + supplement)
• Vitamin D: 800-2000 IU/day; maintain 25-OH Vitamin D >30 ng/mL

2. Exercise:

• Weight-bearing exercise (walking, jogging)
• Resistance training (to maintain muscle and bone strength)
• Balance exercises (to reduce fall risk)

3. Lifestyle Modifications:

• Quit smoking
• Limit alcohol
• Fall prevention strategies (home safety, vision check)

4. Medications to Prevent/Treat Bone Loss:

Bisphosphonates:

• Zoledronic acid (Reclast®): IV infusion once yearly
• Alendronate (Fosamax®): Oral, weekly
• Mechanism: Inhibit bone resorption (breakdown)

Denosumab (Prolia®, Xgeva®):

• Subcutaneous injection every 6 months
• Mechanism: Blocks RANKL, reducing bone breakdown
• MORE effective than bisphosphonates in ADT patients
• Also reduces skeletal-related events in men with bone metastases

When to start bone-protective medication:

• Osteoporosis: T-score ≤ -2.5 on DEXA
• Low bone mass (osteopenia) + high fracture risk (FRAX 10-year hip fracture risk ≥3% or major osteoporotic fracture risk ≥20%)
• History of fragility fracture
• Some guidelines recommend prophylactic treatment for all men on long-term ADT

Bone Metastases:

Prostate cancer commonly spreads to bones (bone metastases). This causes:

• Bone pain
• Pathologic fractures
• Spinal cord compression
• Hypercalcemia

Treatment for Bone Metastases:

• Denosumab (Xgeva®): 120 mg monthly; prevents skeletal-related events
• Zoledronic acid: Alternative
• Radiation therapy: For pain control

Intermittent ADT:

For some men, intermittent ADT (cycling on and off) may reduce side effects (including bone loss) while maintaining cancer control. Discuss with your oncologist.