A prospective observational study is performed to determine factors affecting bone mass and fracture risk. Detailed demographic and clinical information is obtained from a large number of volunteers, and bone mass is monitored over time. The data obtained from 2 specific groups of women are shown below. Which of the following factors is most likely present in group A?

Question

A prospective observational study is performed to determine factors affecting bone mass and fracture risk.  Detailed demographic and clinical information is obtained from a large number of volunteers, and bone mass is monitored over time.  The data obtained from 2 specific groups of women are shown below.  Which of the following factors is most likely present in group A?

Quizplus · Accepted Answer

11ec160b_3d03_c096_9249_ab86c45b0057_MD0001_00 Bone mass in adulthood is determined by peak bone mass and the subsequent rate of bone loss. Most of the variation in peak bone mass is genetically determined, but environmental factors such as nutritional status (eg, calcium and vitamin D intake) and physical activity also have a significant impact. Establishment of a high peak bone mass during early adulthood is important because bone mass subsequently declines with age. By convention, osteoporosis is defined as a bone density that is 2.5 or more standard deviations below the mean (T score ≤ -2.5) for peak young adult bone density. The subjects in group A show a higher peak bone mass, slightly lower rate of post-peak bone loss, and higher late-life bone mass than the subjects in group B. This is consistent with the effects of regular exercise, especially weight-bearing exercise. In contrast, factors that lead to a lower peak bone mass include genetic and ethnic factors (eg, Asian or Caucasian ethnicity), chronic inflammatory disease, exposure to glucocorticoid medications, and sedentary lifestyle. In addition, prolonged caloric deficits (often seen with excessive exercise) can lead to functional hypothalamic amenorrhea, suppression of estrogen production, and rapid bone loss. (Choice A) Estrogens have an anabolic effect on bone by increasing osteoblastic activity and decreasing osteoclastic activity. Loss of estrogen effect (eg, menopause, premature ovarian failure) causes accelerated bone loss. (Choice C) Bone density is proportional to BMI. BMI <22 kg/m² (or weight <57.6 kg [127 lb]) is associated with increased risk for osteoporosis. (Choice D) Smoking causes accelerated bone loss and is a major risk factor for osteoporosis and osteoporotic fractures. (Choice E) Chronic glucocorticoid use is a major risk factor for osteoporosis. Glucocorticoids decrease the gastrointestinal absorption of calcium, inhibit collagen synthesis by osteoblasts, decrease GnRH (leading to hypogonadism), and increase urinary calcium loss. Educational objective: Regular exercise leads to increased peak bone mass, a reduced rate of bone loss, and a decreased risk of osteoporosis. __________ References: Exercise for preventing and treating osteoporosis in postmenopausal women. (http://www.ncbi.nlm.nih.gov/pubmed/21735380)

A Prospective Observational Study Is Performed to Determine Factors Affecting