For each item related to bone metabolism A–E, select the best option for its functional descrip-tion from the following list

A. Option 4 Results in impaired calcification of bone in children. Rickets is due to lack of vitamin D in children. Poor calcium absorption in the gut results in bones with low mineral content that are easily deformed.

B. Option 2 Results in bone formation. Osteoblasts are bone-forming cells that can lay down collagen and other proteins for the bone matrix.

C. Option 1 Results in decalcification of bone in adults. Osteomalacia is due to lack of Vitamin D in adults, usually childbearing women. It results in demineralization and deformation of the bones. When this affects pelvic bones, it may interfere with normal parturition.

D. Option 3 Results in breakdown of bone matrix. Osteoporosis is caused by loss of bony matrix and the resulting bone weakness permits easy bone fracture to occur, especially in the elderly.

E. Option 5 Results in inhibition of bone resorption. Calcitonin is a hormone secreted by the parafollicular cells of the thyroid gland. It lowers the blood calcium level by inhibiting bone resorption.