Abnormalities of parathyroid hormone secretion in elderly women that are reversible by short term therapy with 1,25-dihydroxyvitamin D3.
Serum PTH concentrations increase with aging and may play an important causal role in age-related bone loss. To better define possible PTH secretory abnormalities with aging, we studied 10 young (aged 27-34 yr) and 10 elderly (aged 71-77 yr) women using sequential infusions of calcium and EDTA. To assess possible age-related resistance of PTH secretion to modulation by 1,25-dihydroxyvitamin D [1,25-(OH)2D], the infusions were repeated after 1 week of oral 1,25-(OH)2D3 therapy (1 microgram/day). Baseline serum intact PTH concentrations were higher in the elderly compared to the young women (mean +/- SEM, 3.8 +/- 0.5 vs. 2.7 +/- 0.4 pmol/L; P = 0.03). In addition, the elderly women had a significantly higher maximal PTH response to hypocalcemia compared to the young women (16.6 +/- 1.1 vs. 12.8 +/- 1.0 pmol/L; P = 0.03). The elderly women also had a greater nonsuppressible component of PTH secretion (0.8 +/- 0.1 vs. 0.4 +/- 0.1 pmol/L; P < 0.001). The set-point for PTH secretion, however, was identical in the elderly and young women (1.18 +/- 0.01 vs. 1.19 +/- 0.01 mmol/L; P = NS). After 1,25-(OH)2D3 administration, both groups had similar reductions in baseline and maximally stimulated PTH levels, indicating that elderly women have normal responsiveness to 1,25-(OH)2D3 suppression of PTH secretion. In addition, maximally stimulated PTH levels in the 1,25-(OH)2D3-treated elderly women decreased to the pretreatment values of young women (13.3 +/- 1.1 vs. 12.8 +/- 1.0 pmol/L; P = NS). thus, elderly women have greater basal, maximal, and nonsuppressible levels of PTH secretion, without alterations in the set-point. These abnormalities are similar to those found in patients with secondary hyperparathyroidism and parathyroid hyperplasia. Further, the abnormal PTH secretory dynamics in elderly women are reversible by short term 1,25-(OH)2D3 therapy.
Ledger
G A
GA
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905.
Burritt
M F
MF
Kao
P C
PC
O'Fallon
W M
WM
Riggs
B L
BL
Khosla
S
S
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002112:Calcifediol / Q000097:blood; D002117:Calcitriol / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*; D002118:Calcium / Q000097:blood; D004351:Drug Resistance; D004492:Edetic Acid; D005260:Female; D006801:Humans; D010281:Parathyroid Hormone / Q000097:blood / Q000378:metabolism*
D010281:Parathyroid Hormone; D004492:Edetic Acid; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium