Different patterns of global and regional skeletal uptake of 99mTc-methylene diphosphonate with age: relevance to the pathogenesis of bone loss.
Bone turnover changes with age have been shown by both histomorphometric and scintimetric methods; fewer studies have been performed on the regional differences of bone remodeling in the aging skeleton. To noninvasively investigate this issue, we evaluated the age-related patterns of global and regional bone uptake of 99mTc-methylene diphosphonate (MDP) in a large sample of healthy women.


METHODS
In a group of 84 healthy women (33 pre- and 51 postmenopausal), the uptake of 99mTcMDP was semiquantitatively measured in 5 regions of interest. Total-body digital scans (TBDSs) were acquired at 5 min and at 4 h. Five regions of interest were drawn on the skeleton as a whole, on the lumbar spine, on the iliac wing, on the femoral neck, and on the femoral diaphysis of the 4-h TBDS. Regional skeletal uptake of the lumbar spine (LS-RSU), of the iliac wing (IL-RSU), of the femoral neck (FN-RSU), and of the femoral diaphysis (FD-RSU) was calculated as percentage injected dose retained in these skeletal segments at 4 h.


RESULTS
As expected, in postmenopausal women the global skeletal uptake (GSU) values were higher than those in premenopausal women (40.7 +/- 5.9 percentage injected dose [%ID] versus 35.1 +/- 4.2 %ID; P < 0.0001). GSU correlated positively with age (r = 0.70; P < 0.001), but the addition of years since menopause to the regression model did not ameliorate the regression. On the other hand, LS-RSU (r = -0.55; P < 0.0001), IL-RSU (r = -0.45; P < 0.0001), and FN-RSU (r = -0.22; P < 0.005) decreased significantly, whereas FD-RSU increased significantly (r = 0.39; P < 0.001) with age; the same regressions were not influenced significantly by the addition of menopausal duration to the regression model. The strongest correlation among the different RSUs was that found between LS-RSU and IL-RSU (r = 0.63; P < 0.001). Moreover, the linear regression coefficients of the various RSUs with age were all significantly different from each other (P < 0.001).


CONCLUSIONS
Our data show that the GSU of 99mTc-MDP increases with age, whereas different skeletal segments display a variable degree of turnover activation at different ages. This could ultimately induce the different rates of bone loss of different skeletal segments at various ages and, consequently, their variable propensity to fracture.
Carnevale
V
V
Department of Internal Medicine, Istituto di Ricovero e Cura a Carattere Scientifico Casa Sollievo della Sofferenza, San Giovanni Rotondo Foggia, Italy.
Dicembrino
F
F
Frusciante
V
V
Chiodini
I
I
Minisola
S
S
Scillitani
A
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D001842:Bone and Bones / Q000000981:diagnostic imaging* / Q000502:physiology; D005260:Female; D006801:Humans; D007558:Italy; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000000981:diagnostic imaging*; D017698:Postmenopause; D017697:Premenopause; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012016:Reference Values; D012044:Regression Analysis; D013669:Technetium Tc 99m Medronate / Q000493:pharmacokinetics*; D044465:White People
D019275:Radiopharmaceuticals; D013669:Technetium Tc 99m Medronate