Calcium, phosphorus and vitamin D disorders in uremia.
BACKGROUND
Alterations in calcium, phosphate (P) and vitamin D metabolism play a critical role in the development of secondary hyperparathyroidism (SH), parathyroid hyperplasia and soft tissue and vascular calcification.


METHODS
Studies were performed in uremic dogs and rats fed a low and high P diet over a period of 1-4 months. In addition, in vitro studies were performed in normal parathyroid glands incubated in culture media containing 0.2 mM P (low) or 2.0 mM P (high).


RESULTS
Uremic rats maintained on a low P diet did not develop SH or parathyroid hyperplasia. There was an enhancement of p21, the suppressor of the cell cycle, in these parathyroid glands. Opposite results were obtained using a high P diet. There was an enhancement of transforming growth factor-alpha and epidermal growth factor receptor, known enhancers of cell proliferation. In vitro studies demonstrated the direct effect of P on parathyroid hormone secretion.


CONCLUSIONS
Early dietary P restriction prevents the development of SH and parathyroid hyperplasia. If dietary P restriction is applied to rats with established SH, there is a significant amelioration of SH and parathyroid hyperplasia. In addition, control of serum P in uremic patients is crucial in the prevention of vascular calcification.
Slatopolsky
Eduardo
E
Washington University School of Medicine, Department of Medicine, Renal Division, St. Louis, Mo., USA.
Brown
Alex
A
Dusso
Adriana
A
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000209:etiology*; D006965:Hyperplasia; D010279:Parathyroid Diseases / Q000209:etiology* / Q000473:pathology; D010758:Phosphorus / Q000378:metabolism*; D014511:Uremia / Q000150:complications* / Q000378:metabolism*; D014807:Vitamin D / Q000378:metabolism*
D014807:Vitamin D; D010758:Phosphorus; D002118:Calcium