This quantity is characterized by broadband ultrasound attenuation when measuring it using quantitative ultrasound. It doesn’t have to do with lipids, but mutations in LPR5 that control this quantity are present in Van Buchem disease. Age, height, weight, TBS, and this quantity are the main inputs of the FRAX tool. (15[1])Jean Lobstein described a condition in which this quantity is low that often results in blue sclerae. A decrease in this quantity is a common side effect of (*) puberty blockers and androgen (10[2])deprivation therapy. This quantity is typically measured by DEXA scans. Inability to form type I collagen leads to this quantity being low in a condition partially called "imperfecta." Alendronate and zoledronate are bisphosphonates that increase this quantity which is lowered by parathyroid hormone. For 10 points, name this quantity that is low in rickets and osteoporosis. ■END■