Postoperative evaluation of patients with acromegaly: clinical significance and timing of oral glucose tolerance testing and measurement of (free) insulin-like growth factor I, acid-labile subunit, and growth hormone-binding protein levels.
BACKGROUND
It is not exactly known when patients with acromegaly should be evaluated for cure after transsphenoidal adenomectomy (TA).


OBJECTIVE
The objective of this study was to define the optimal time point of postoperative evaluation by serial measurements of glucose-suppressed GH levels [oral glucose tolerance test (OGTT)] and the GH-dependent parameters IGF-I, free IGF-I, acid labile subunit (ALS), and GH-binding protein (GHBP).


METHODS
We describe a prospective study with 1-yr follow-up.


METHODS
The study was conducted at a university hospital.


METHODS
Seventeen patients with acromegaly were included in the study.


METHODS
The main outcome measures were OGTT results at 1, 2, 3, 8, and 12 wk after TA; weekly measured GH, (free) IGF-I, ALS, and GHBP levels up to 12 wk; and total IGF-I levels measured at 52 wk.


RESULTS
Postoperatively, nine patients were in remission with an OGTT GH nadir of less than 0.5 microg/liter and normalized IGF-I levels, whereas eight patients had persistent acromegaly. In both cured and noncured patients, OGTT results at 1 wk after TA were highly reproducible over time. In contrast, early postoperative IGF-I levels fluctuated and only stabilized at 12 wk. In all cured patients, free IGF-I levels rapidly normalized within 2 wk after TA (specificity, 100%). Preoperative ALS levels were elevated in all patients and normalized only in the cured patients after TA (specificity, 89%). Preoperative GHBP levels were low and increased from 2 wk after surgery.


CONCLUSIONS
We show that in the postoperative evaluation of patients with acromegaly, already 1 wk after surgery, an OGTT using 0.5 microg as the GH nadir cutoff value has a high predictive value for cure, whereas early IGF-I levels show varying patterns toward stabilization. Therefore, IGF-I should be measured as a predictive parameter not within 3 months after surgery. Free IGF-I and ALS levels may have an additional value in the postoperative assessment of disease activity.
Feelders
R A
RA
Division of Endocrinology, Erasmus Medical Center, Rotterdam, The Netherlands. r.feelders@erasmusmc.nl
Bidlingmaier
M
M
Strasburger
C J
CJ
Janssen
J A M J L
JA
Uitterlinden
P
P
Hofland
L J
LJ
Lamberts
S W J
SW
van der Lely
A J
AJ
de Herder
W W
WW
D000172:Acromegaly / Q000601:surgery*; D000328:Adult; D000368:Aged; D002352:Carrier Proteins / Q000097:blood*; D005260:Female; D005951:Glucose Tolerance Test; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011184:Postoperative Period; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome
D002352:Carrier Proteins; D006023:Glycoproteins; D018972:Insulin-Like Growth Factor Binding Protein 3; C075944:insulin-like growth factor binding protein, acid labile subunit; D007334:Insulin-Like Growth Factor I; C051815:somatotropin-binding protein