Gender-specific relationship between serum free and total IGF-I and bone mineral density in elderly men and women.
OBJECTIVE
Little is known about the association between free IGF-I levels and bone mineral density (BMD).


METHODS
A cross-sectional study of 218 healthy subjects (103 men, 115 women, age 55-80 years) was carried out.


METHODS
Fasting serum free IGF-I, total IGF-I, estradiol and sex hormone-binding globulin (SHBG) levels were measured. The ratio of estradiol to SHBG was used as an index of free estradiol. BMD measurements were performed by dual-energy X-ray absorptiometry of the lumbar spine and the proximal femur.


RESULTS
In multivariate analyses with BMD of the lumbar spine as the dependent variable and serum free IGF-I, age, body mass index (BMI) and the free estradiol index as independent variables, the free IGF-I was positively related to the BMD of the lumbar spine in men (P = 0.02) but not in women. When the same analyses for the lumbar BMD were performed with total serum IGF-I the association was also only statistically significant in men (P = 0.05). In multivariate analyses with the trochanter BMD as the dependent variable and serum free IGF-I, total IGF-I, age, BMI and the free estradiol index as independent variables, the associations between (free and total) IGF-I and the trochanter BMD in men was of borderline significance.


CONCLUSIONS
In elderly men free and total IGF-I were positively related to lumbar BMD, while (free and total) IGF-I was borderline positively related to trochanter BMD. As these relationships were not observed in elderly women, we suggest a weak gender-specific anabolic effect of IGF-I on BMD on trabecular bone.
Department of Internal Medicine III, Erasmus University, Rotterdam, The Netherlands.
J A
JA
Janssen
H
H
Burger
R P
RP
Stolk
D E
DE
Grobbee
F H
FH
de Jong
S W
SW
Lamberts
H A
HA
Pols
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D015519:Bone Density / Q000502:physiology*; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008161:Lumbosacral Region; D008297:Male; D008875:Middle Aged; D017678:Sex Distribution
D007334:Insulin-Like Growth Factor I