Biochemical features of high serum alkaline phosphatase (ALP), high parathyroid hormone (PTH) with or without low 25 hydroxyvitamin D (25OHD) concentrations are common to both rickets and osteomalacia.
Reduced 1,25(OH)<sub>2</sub>D-mediated intestinal and renal calcium transport can reduce calcium availability, increase parathyroid hormone secretion and phosphaturia, and impair mineral availability for normal matrix mineralization, resulting in reduced growth plate mineralization and osteomalacia.
In these two patients whose plasma concentration of PTH was normal (determined by radioimmunoassay). neither vitamin D nor phosphate therapy had been given during the past 10 yr. Two normal men and a hypophosphatemic man with intestinal malabsorption, hypocalcemia, and osteomalacia served as control subjects.