Mandy is a 16-year-old competitive figure skater who practices several hours a d

Question

Mandy is a 16-year-old competitive figure skater who practices several hours a day with her coach at the skating arena. Because of her extremely active lifestyle and restricted diet to maintain her athletic physique, she experiences ongoing amenorrhea. One day during practice, she landed a jump and fell to the ice in pain. Her left foot swelled up almost immediately, making it difficult for her coach to remove the skate. At the hospital, radiographs revealed a fracture of the fifth metatarsal bone and general radiolucency of all the bones in her foot. A follow-up DXA revealed a bone mass of 2.7 standard deviations below mean.

What is the etiology of Mandy’s premature osteoporosis, and how her condition is thought to contribute to a decrease in bone density?

Knowing what you do about bone mineralization, why does a deficiency of estrogen in women lead to osteoporotic change?

Osteoporosis and osteomalacia both involve abnormal bone mineralization. What are the general macroscopic differences of these two conditions?

Explanation / Answer

1. Bone formation and resorption is natural process and continously goes on for the growth, development and remodling of bones. Bone formation indicated the formation of new bone while resorption indicates the break down and absorption of old bone for remodling of bones. If there is an imbalance occurs between these two processes then osteoprocess may arise. In the case of osteoporosis the body may fail to form sufficient new bone, or too much old bone may be reabsorbed, or both. Two essential minerals calcium and phosphate play a major role in the bone growth and development. Here Mandy is not taking proper diet to maintain her athletic physic which cause deficieny of these two essential minerals which causes osteoprosis. Due to dificiency of these two minerals, the level of calcium and phosphate decrease in blood. To maitain this reduced level of these minerals, the process of resorption increase which causes leaching of these minerals from bones to the blood and hence the density of bone decreases. Also improper diet by Mandy causes hormonal imbalance which results in fluctuation of estrogen level responsible for menstrual cycle and thus causes amenorrhea. Decreased level of estrogen also affect the osteoclast differentiation which is responsible for bone resorption process and hence affect the density of bone.

2. Mineralization of bone is an essential process for its hardness and strength and involves a well organised process in which calcium phosphate are produced by bone-forming cells and laid down in precise amounts within the bone’s fibrous matrix or scaffolding. Estrogen inhibits differentiation of osteoclast cells (responsible for bone resorption -leaching of minerals from bones to the blood for remodeling of bones). Hence deficiency of estrogen enhance resorption process which results in osteoporotic condition.

3. Osteoporosis and osteomalacia both are bone mineralization disorder, but in osteoporosis, the bones are porous and brittle, while in osteomalacia the bones are soft. This difference in bone consistency is related to the ratio of mineral to organic material. In osteoporosis, the mineral-to-collagen ratio is within the normal range, while in osteomalacia, the proportion of mineral composition is decreases in comparision to organic mineral content.

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