CYP19A1 and postmenopausal osteoporosis: One example of differences between male and female mice has been found in aromatase-deficient mice, where the female aromatase-ablation mice had an increase in bone turnover resembling early postmenopausal osteoporosis, whereas the male aromatase-deficient mice showed decreases in both osteoblastic and osteoclastic surfaces similar to age-related osteopenia compared with WT littermates (Oz et al., 2000).