Longitudinal analysis of the relationship between serum insulin-like growth factor-I and radiographic knee osteoarthritis.
OBJECTIVE
To examine the relation between serum insulin-like growth factor I (IGF-I) levels and both incident and progressive radiographic knee osteoarthritis (OA) in the Framingham Osteoarthritis Study.


METHODS
Subjects had bilateral weight-bearing, anterior-posterior knee radiographs performed in 1983-1985 and again in 1992-1993. IGF-I levels were measured from blood specimens obtained in 1988-1989 by a competitive binding radio-immunoassay (RIA) after separation with octadecasilyl-silica cartridges of serum IGF-I from binding proteins. Participants without baseline radiographic OA [Kellgren and Lawrence grades (K&L) = 0-1] were classified as having incident disease if they had K&L > or = 2 grades at follow-up. Progressive OA was defined as an increase in K&L score of > or = 1 in knees with baseline OA (K&L > or = 2). All analyses were knee-based and sex-specific. We examined IGF-I tertiles in relation to the risk of incident and progressive radiographic OA separately, adjusting for age, body mass index (BMI), and baseline K&L score, and used generalized estimating equations to adjust for the correlation between fellow knees.


RESULTS
Four hundred and forty-one participants had knee radiographs and serum IGF-I levels measured. No associations were found for serum IGF-I levels and incident [women: OR = 0.9 (0.6-1.7), men OR = 1.2 (0.6-2.6)] or progressive [women OR = 0.9 (0.6-1.6), men OR = 0.9 (0.3-3.0)] radiographic knee OA in either sex. Neither did we observe any association between IGF-I and worsening of individual radiographic features of OA (i.e., osteophyte growth and joint space loss).


CONCLUSIONS
In summary, this longitudinal study did not demonstrate any association of serum IGF-I and incident or progressive radiographic knee OA. Further studies are needed to clarify the role of IGF-I in OA.
Fraenkel
L
L
Arthritis Center, Boston University Medical Center, Massachusetts 02118, USA. fraenkel@bu.edu
Zhang
Y
Y
Trippel
S B
SB
McAlindon
T E
TE
LaValley
M P
MP
Assif
A
A
Adams
K E
KE
Evans
S R
SR
Felson
D T
DT
D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008137:Longitudinal Studies; D008297:Male; D020370:Osteoarthritis, Knee / Q000097:blood* / Q000000981:diagnostic imaging; D011859:Radiography; D011863:Radioimmunoassay / Q000379:methods
D007334:Insulin-Like Growth Factor I