By the way, doctor: Do I need CTX testing during a Fosamax "holiday"?
During resorption, bone minerals (calcium and phosphate) and bone matrix (mostly collagen) are released into the bloodstream. Enzymes in the blood break down the collagen into peptides called bone turnover markers, which can be measured in blood and urine. CTX is a marker of bone resorption; an elevated blood level is a sign of accelerated resorption (and bone turnover), sometimes resulting from low estrogen. Bisphosphonate drugs, which are used to treat osteoporosis, block resorption and thus cause CTX levels to fall. This is true of all bisphosphonates, including ibandronate (Boniva), risedronate (Actonel), zoledronic acid (Reclast), and alendronate (Fosamax).
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