Other factors that have been shown to affect bone homeostasis in NF1 are the elevated renal excretion of calcium, reduced levels of total and ionized plasma calcium and magnesium levels, and increased circulating levels of parathormone (PTH) that were associated with secondary hyperparathyroidism [17,31,39,44,47]. The gene discussed is PTH; the disease is neurofibromatosis type 1.