Studying Phosphorus Metabolism
Studying Phosphorus Metabolism
Phosphorus and phosphate irons play critical roles in bone structure and essential cellular
 functions.

 The purpose of this study is to learn more about the factors and hormones that regulate
 phosphorus in the body by collecting blood and urine samples from patients with disorders of
 phosphate control.

 Both children and adults will be enrolled in this study. Researchers will collect blood and
 urine samples from participants on multiple occasions (2 to 6 times). Some blood specimens
 will be taken after an overnight fast and participants may be asked to collect all their
 urine during a 24-hour period. Researchers will analyze these blood and urine samples to
 better understanding how the body handles phosphorus.
Phosphorus and phosphate ions play an important role in cellular metabolism as well as bone
 structure. Scientific evidence suggests that, in addition to Vitamin D and PTH systems, novel
 factors, such as Fibroblast Growth Factor 23 (FGF-23) and Matrix extracellular
 phosphoglycoprotein (MEPE), may play an important role in phosphorus regulation. These
 factors have been best studied in rare genetic and acquired phosphate wasting disorders such
 as tumor induced osteomalacia (TIO), X linked hypophosphatemia (XLH) and autosomal dominant
 hypophosphatemic rickets (ADHR). Patients with other abnormal phosphate regulating states
 such as hyperparathyroidism and hypoparathyroidism, pseudohypoparathyroidism etc. undergoing
 phosphorus-altering interventions may provide important insight into the role of these
 hormones.

 We are proposing an observational study with collection of blood and urine samples to study
 both established (e.g. mineral ions, bone markers, PTH-Vit D system, TMP-GFR) and novel (e.g.
 FGF-23 and MEPE) constituents of the phosphorus metabolism pathway. Patients with abnormal
 phosphorus regulating states will be enrolled and we will study the natural history of their
 disease and the effects of specific interventions that are likely to change phosphorus
 balance.

 The outcome will potentially aid understanding of this new field of mineral regulating
 hormones and generate both interest and research in phosphorus metabolism. It is hoped that
 this will also encourage clinical trials in treatment of phosphate wasting disorders.
INCLUSION CRITERIA:

 Patients of any age, gender or ethnicity who will help fulfill the objectives laid out in
 Section II.

 We propose to study patients primarily enrolled in other clinical center protocol(s). They
 will continue to receive treatment/ interventions per the original protocols.

 EXCLUSION CRITERIA:

 Patients with significant cognitive impairment who are unable to give informed consent or
 patients having other significant mineral disturbances that could confound the parameters
 being studied will be excluded.