PTH and Renal insufficiency: Approximately 20% of American adults aged 65 and older experience moderate to severe renal dysfunction.[23] A glomerular filtration rate below 60 mL/min/1.73 m2 results in phosphate retention, which subsequently elevates parathyroid hormone levels and reduces 1,25-dihydroxyvitamin D concentrations, both of which adversely affect BMD.[24] Subclinical renal insufficiency is a prevalent condition that often eludes detection through standard clinical chemistry assessments, such as BUN or Cr measurements.