J. Silver et al., NEW INSIGHTS INTO THE REGULATION OF PARATHYROID-HORMONE SYNTHESIS ANDSECRETION IN CHRONIC-RENAL-FAILURE, Nephrology, dialysis, transplantation, 11, 1996, pp. 2-5
The main factors which regulate parathyroid hormone (PTH) production a
re calcium, phosphate, vitamin D and the sex steroids, estrogens and p
rogestagins. Hypocalcaemia leads to increased PTH secretion in seconds
and minutes, gene expression in hours and parathyroid cell number in
weeks and months. Hypercalcaemia leads to a decrease in PTH secretion
by its action on the parathyroid cell calcium receptor and no decrease
in PTH mRNA concentrations. There is now convincing evidence that pho
sphate regulates the parathyroids independent of its effect on serum c
alcium and 1,25-dihydroxyvitamin D3 (1,25(OH)(2)D-3). In vivo in rats
hypophosphataemia markedly decreases PTH mRNA and serum PTH independen
t of its effect on serum calcium and 1,25(OH)(2)D-3. Clinical studies
also indicate that phosphate regulates the parathyroids independent of
its effect on serum calcium and 1,25(OH)(2)D-3. 1,25(OH)(2)D-3 itself
has a marked effect on the parathyroids where it decreases PTH gene t
ranscription by a direct action. Parathyroid cell proliferation is reg
ulated by dietary calcium and phosphate with hypocalcaemia markedly in
creasing and hypophosphataemia markedly decreasing the number of proli
ferating cells. The application of basic science findings of how calci
um, phosphate and 1,25(OH)(2)D-3 regulate the parathyroids has led to
an efficient and safe prescription for the management of the secondary
hyperparathyroidism of chronic renal failure which is the maintenance
of a normal serum calcium and phosphate and the careful use of bolus
doses of 1,25(OH)(2)D-3.