
the relationship between vitamin d and parathyroid
hormone
marit von stedingk
the effect of parathyroidectomy and parathy-
roid hormone administration upon the concentra-
tions of plasma calcium and phosphate have been
measured in vitamin d-deficient rats and the re-
sults compared to those observed in d-fed ani-
mals.  also, the influence of dietary calcium and
phosphate content upon these responses has been
investigated.  parathyroidectomy in the d-fed ani-
mal results in a rapid fall in plasma calcium and a
biphasic plasma phosphate response with an initial
fall followed by a striking rise.  in contrast,
parathyroidectomy in the d-deficient rat is fol-
lowed by no significant change in plasma calcium
and an immediate rise in plasma phosphate that
can be prevented by the administration of para-
thyroid hormone.  dietary phosphate restriction
abolished the effect of parathyroidectomy in both
groups of animals.
administration of a dose of 500 u of hormone
to the intact d-deficient rat had little influence
upon plasma calcium; a dose of 2,000 u did in-
crease plasma calcium.  a dose of 25 u was suffi-
cient to increase the plasma calcium of the d-fed
animal.  these results are discussed in relation
to the effects of vitamin d and parathyroid hor-
mone upon mitochondrial metabolism.
