Usefulness of different biochemical markers of the insulin-like growth factor (IGF) family in diagnosing growth hormone excess and deficiency in adults
P. Marzullo et al., Usefulness of different biochemical markers of the insulin-like growth factor (IGF) family in diagnosing growth hormone excess and deficiency in adults, J CLIN END, 86(7), 2001, pp. 3001-3008
The diagnostic approach to acromegaly and GH deficiency frequently includes
measurement of several components of the insulinlike growth factor (IGF) s
ystem. IGF-I levels are reported to be good predictors of active and cured
acromegaly, but are commonly found within the normal age-adjusted range in
adult GH-deficient (GHD) patients. Circulating concentrations of IGF-bindin
g protein-3 (IGFBP-3), acid-labile subunit (ALS), and free IGF-I reflect th
e GH secretory status, but their diagnostic accuracy is still debated. In t
his study serum levels of total and free IGF-I, IGFBP-3, ALS, and IGFBP-3-I
GF-I and IGFBP-3-ALS complexes were determined in patients previously diagn
osed with active (n = 67) or inactive (n = 16) acromegaly and adult GHD (n
= 34) and compared with results obtained in 58 healthy controls.
In healthy subjects, IGF-I, IGFBP-3, ALS, and both IGFBP-3 complexes declin
ed with age; a correlation was found between IGF-I and IGFBP-3 (r = 0.59; P
< 0.001), ALS (r = 0.67; P < 0.001), and free IGF-I (r = 0.40; P < 0.05).
Active acromegalic patients showed a significant increase in all parameters
tested. IGF-I concentrations were above +2 so in 100% of patients, whereas
slightly lower sensitivities were shown for IGFBP-3 (85%), ALS (88%), and
free IGF-I (94%). In this group, IGF-I exhibited a slightly higher correlat
ion with IGFBP-3 (r = 0.83; P < 0.001) than with ALS levels (r = 0.78; P <
0.001). In cured acromegalic patients, we observed the normalization of all
parameters but free IGF-I levels.
Adult GHD patients showed a significant reduction of all hormones. Unlike a
ctive acromegalic patients, all parameters had only a modest sensitivity in
GHD; suppression below -2 Sn was observed in 41% of GHD patients for IGF-I
, 47% for IGFBP-3, 32% for ALS, and 35% for free IGF-I measurements. Previo
us radiotherapy and GH peak response below 3 mug/L were associated with sig
nificantly lower IGF-I, IGFBP-3, and ALS levels. IGF-I levels were signific
antly correlated to ALS (r = 0.68; P < 0.001) and IGFBP-3 (r = 0.64; P <les
s than> 0.001) as well as with free IGF-I (r = 0.67; P < 0.001) levels. By
multiple regression analysis, the number of anterior pituitary hormones imp
aired was the most predictive indicator of IGF-I, IGFBP-3, and free IGF-I l
evels in GHD patients; conversely, the GH peak response better anticipated
ALS concentrations.
The pattern of IGFBP-3 complexes paralleled previous hormonal findings. In
active acromegalic patients, IGFBP-3-IGF-I levels were 5.4-fold higher than
in controls and were above +2 SD in 95% of patients, whereas IGFBP-3-ALS l
evels were elevated in 15% of cases: On the other hand, both IGFBP-3 comple
xes were able to predict GHD; in only a minority of cases.
Taken together, these data support the diagnostic role of IGF-I in acromega
ly and suggest that free IGF-I and the IGFBP-3-IGF-I complex can assist dia
gnostic strategies in this condition. All markers are of limited predictive
value in adult GHD, as hormonal values are commonly found within the norma
l limits. In these patients, low IGFBP-3 and IGF-I concentrations can add f
urther clinical information on the residual GH activity.