PTH and hip fracture: 2% new hip fractures The incidence rate was higher among patients in the lower quartiles of serum Mg. Lower serum Mg levels were significantly associated with an increased risk of hip fracture.The risk of hip fracture was not elevated in HD patients with mild hypermagnesemia.The population-attributable fraction of serum Mg level for incident hip fractures was 13.7% which was much higher than that of serum Ca, P, and PTH levels.