Vol. 282, Issue 3, E557-E563, March 2002
Parathyroid gland volume increases with postmaturational
aging in the rat
Bernard
Halloran1,
Per
Udén2,
Quan-Yang
Duh3,
Shoichi
Kikuchi1,4,
Tracy
Wieder1,
Jay
Cao1, and
Orlo
Clark4
1 Division of Endocrinology and 3 Surgical and
Medical Service, Veterans Affairs Medical Center and Department of
Medicine, University of California, San Francisco 94121;
4 Departments of Medicine and Surgery, University of
California/Mt. Zion Medical Center, San Francisco, California
94115; and 2 Department of Surgery, Malmo Allmanna
Sjukhus, Lund University, S-214 01 Malmo, Sweden
To examine the
pathophysiology of the age-related rise in the plasma concentration of
parathyroid hormone (PTH), we studied the relationships among plasma
immunoreactive PTH (iPTH), parathyroid gland volume, parathyroid cell
proliferation rate, renal function, and blood Ca2+ in male
Fischer 344 rats aged 6-28 mo. Plasma iPTH increased 2.5-fold
between 6 and 28 mo and correlated with parathyroid gland volume
(r = 0.87). Gland volume began to increase as early as 6-12 mo of age and by 28 mo was threefold greater than at 6 mo. Gland expansion was a consequence of hyperplasia stimulated in part by
an increase in cell proliferative activity late in life. Blood
Ca2+ and plasma inorganic phosphorus did not change
significantly with age. Glomerular filtration rate decreased with age
but only after the age of 24 mo. Unlike what has been observed in the
human, these data suggest that the age-related increase in plasma iPTH in the rat is linked to parathyroid gland hyperplasia and that early
gland growth does not appear to be associated with hypocalcemia or
renal insufficiency, but rather to developmentally related metabolic
changes. Later in life (>24 mo), the increase in parathyroid cell
proliferation rate, further hyperplastic expansion of the gland, and
increase in iPTH secretion appear to be associated with renal insufficiency.
parathyroid hormone; renal function; glomerular filtration rate
