TGFB1 and postmenopausal osteoporosis: The concentration of TGF-β1 used in this study (25 ng/mL) was selected based on its clear inhibitory effect on osteoblast maturation, while maintaining (patho)physiological relevance, as the circulating levels of TGF-β1 in postmenopausal osteoporosis, a disease characterized by inhibited osteoblast differentiation and bone formation, has been shown to be 23.8 ng/mL, as compared to 15.6 ng/mL in age-matched control individuals (12).