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Inorganic Phosphorus Reduces Hypercalciuria During Total Parenteral Nutrition By Enhancing Renal Tubular Calcium Absorption
Author(s) -
Berkelhammer Charles,
Wood Richard J.,
Sitrin Michael D.
Publication year - 1998
Publication title -
journal of parenteral and enteral nutrition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.935
H-Index - 98
eISSN - 1941-2444
pISSN - 0148-6071
DOI - 10.1177/0148607198022003142
Subject(s) - hypercalciuria , calcium , endocrinology , medicine , urinary calcium , parathyroid hormone , chemistry , phosphorus , excretion , calcium metabolism , urinary system , organic chemistry
Background: Increasing the inorganic phosphorus content of total parenteral nutrition (TPN) formulas has been shown to decrease TPN‐induced hypercalciuria in experimental animals and humans. The mechanism of this effect, however, has been uncertain. Methods: By using a randomized cross‐over design, seven patients on cyclic TPN were given otherwise identical formulas providing either 15 or 45 mmol/d of inorganic phosphorus. Urinary calcium excretion, serum ultrafilterable calcium, filtered calcium load, fractional calcium excretion, urinary cyclic adenosine 5′‐monophosphate (cAMP), and serum levels of ionized calcium, parathyroid hormone (PTH), and vitamin D metabolites were determined at the end of each study period. Results: Urinary calcium excretion was significantly lower when the patients received the higher inorganic phosphorus formula. Increasing the inorganic phosphorus in the TPN formula did not change ultrafilterable calcium or filtered calcium load, but significantly reduced fractional calcium excretion. No differences in serum levels of ionized calcium, PTH, 25‐hydroxyvitamin D, 1,25‐dihydroxyvitamin D, or urinary cAMP were observed between treatments. Conclusions: These results demonstrate that increasing the inorganic phosphorus content of the TPN formula decreases urinary calcium excretion by increasing renal tubular calcium resorption. This effect is not due to alterations in the PTH‐1,25‐dihydroxyvitamin D axis, but likely reflects a direct action of inorganic phosphorus on the renal tubules. ( Journal of Parenteral and Enteral Nutrition 22 :142–146, 1998)