Mandy is a 16-year-old competitive figure skater who practices several hours a day with her coach at ...

Mandy is likely demonstrating the effects of the female athletic triad. Disordered eating and intensive exercise in some athletes reduce fat stores and the fat-to-muscle ratio. The result is a decrease in estrogen production by the ovaries with amenorrhea. The reduction in circulating estrogen, coupled with an insufficient intake of vitamin D and calcium, accelerates bone resorption and the formation of osteoporosis.

Estrogen deficiency contributes to the development of osteoporosis in a number of ways. Lowered levels of estrogen encourage an increase in cytokine production that stimulates the proliferation of osteoclast precursors. Furthermore, when estrogen is low, the differentiation of osteoclasts becomes unregulated; osteoclast precursors are more responsive to the RANK ligand, and osteoclastic proliferation occurs. The result is a condition of bone resorption that occurs at a rate that cannot be matched by a compensatory increase in osteoblastic activity.

Osteoporosis is a disease characterized by a decline in bone mass. Osteoporotic bone is porous and brittle with a decreased amount of trabeculae and cortical volume. Osteomalacia, in contrast, is a disease characterized by the undermineralization of bone. Bone tissue exhibiting osteomalacia is soft and weak due to the lack of mineralization. Total bone mass, however, is unchanged.