This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Menopause and HRT, Subject name: Gynaecology & Obstetrics
Osteoporosis in postmenopausal women is defined by T-score of 
Select and explain. 
A. 1 to 2.5 SD, B. 0 to -1 SD, C. -1 to -2.5 SD, D. Below -2.5 SD
D: Below -2.5 SD
Answer: D: Below -2.5 SD 
Explanation: T Score: Standard detions between patient and average peak young adult bone mass. The more negative, the greater the risk of fracture. Z Score: Standard detions between patient and average bone mass for the same sex, age, and weight. A Z score lower than -2.0 (2.5% of the normal population of the same age) requires diagnostic evaluation for causes other than postmenopausal bone loss.The clinical relevance of a bone density measurement in a postmenopausal woman is estimated by using the T Score. For younger women, interpretation utilizes the Z ScoreDefinitions Based on Bone Mineral DensityNormal: 0 to -1 SD from the T-score reference standard (84% of the population) Osteopenia: T-score -1 to -2.5 SD Osteoporosis: T-score below -2.5 SDReference: Clinical Gynecologic Endocrinology; 8th edition; Chapter17; Menopause and the Perimenopausal Transition