Percent changes in (A) bone resorption markers (urinary deoxypyridinoline [Dpd] and N-telopeptide of type I collagen [NTx]) and (B) bone formation markers (serum osteocalcin and N-terminal extension peptide of type I collagen [PINP]) in a group of elderly men (mean age 68 yrs) made acutely hypogonadal and treated with an aromatase inhibitor (Group A), treated with estrogen alone (Group B), testosterone alone (Group C), or both (Group D). See text for details. Asterisks indicate significance for change from baseline: *, P < 0.05; **, P < 0.01; ***, P < 0.001. Adapted from Falahati-Nini et al. (52), with permission.