Clinical Trials

Inclusion Criteria

• Normal men
• Young, aged 25-40 years
• Old, aged 60-80 years

Exclusion Criteria

• Abnormality in any of the screening laboratory studies 
  • If found to have low body stores of vitamin D (serum 25-hydroxyvitamin D of < 20 ng/ml), subjects will be treated with 1000 IU/day of vitamin D for 8 weeks and then rechecked
    • If the level is still < 20 ng/ml, they will receive a second 8 week course of vitamin D
    • If, following that, the level is still < 20 ng/ml, they will not continue in the study and will be referred to their primary physician for further evaluation
• Presence of significant liver or renal disease
• Malignancy (including multiple myeloma)
• Malabsorption
• Diabetes
• Hypoparathyroidism
• Hyperparathyroidism
• Acromegaly
• Cushing’s syndrome
• Hypopituitarism
• Severe chronic obstructive pulmonary disease
• Treatment with any of the following drugs
  • Adrenocorticosteroids (> 3 months at any time or > 10 days within the previous year)
  • Anticonvulsant therapy (within the previous year)
  • Pharmacological doses of thyroid hormone (causing decline of thyroid stimulating hormone below normal)
  • Calcium supplementation of > 1200 mg/d (within the preceding 3 months)
  • Testosterone therapy
  • Teriparatide (within the past year)
  • Bisphosphonates within the past 3 years
• A clinical history of osteoporotic fracture (vertebral, hip, or distal forearm) 
• To avoid confounding by hypogonadism, particularly in the elderly males, we will obtain free testosterone levels in all subjects and exclude those with levels < 9 ng/dL (the lower limit of normal in our laboratory)