CTSK and osteoporosis: Munoz-Torres et al. (23) observed that serum cathepsin K levels were higher in 46 postmenopausal women with osteoporosis (9.4 ± 11 pmol/L) compared with 20 healthy postmenopausal women (6.8 ± 8.1 pmol/L; P < 0.01) and 20 pre-menopausal women (6.3 ± 5.0 pmol/L, P < 0.01).