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Multiple sclerosis is a condition wherein the body's nervous system is weakened by an autoimmune reaction that attacks the myelin sheaths of neurons.
Bisphosphonates were first developed in the nineteenth century. They were first investigated for use in disorders of bone metabolism in the 1960s. They are now used clinically for the treatment of osteoporosis, Paget's disease, bone metastasis, multiple myeloma, and other conditions that feature bone fragility.
Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.
Approximately 15–25% of recognized pregnancies end in miscarriage. However, many miscarriages often occur before a woman even knows she is pregnant.
Although puberty usually occurs in the early teenage years, the world's youngest parents were two Chinese children who had their first baby when they were 8 and 9 years of age.