Serum IGF-1 in the diagnosis of acromegaly and the profile of patients with elevated IGF-1 but normal glucose-suppressed growth hormone.
OBJECTIVE
To report the utility of insulin-like growth factor-1 (IGF-1) as a single biomarker for establishing the diagnosis of acromegaly and to examine the clinical and biochemical profile of patients with an elevated IGF-1 in whom a diagnosis of acromegaly could not be confirmed by means of the oral glucose tolerance test (OGTT).


METHODS
Between the years 1999 and 2010, we identified 101 patients who underwent pituitary surgery and had histologically proven somatotroph adenomas (Group 1, Gr 1). We selected 149 patients with non-growth hormone (GH) secreting pituitary macroadenomas (Gr 2, n = 97) and microadenomas (Gr 3, n = 52) to serve as control subjects. In addition, we identified 34 patients with elevated IGF-1values in whom acromegaly could not subsequently be proven by the OGTT (Gr 4).


RESULTS
IGF-1 was elevated in all patients with acromegaly prior to therapy with a median (range) standard deviation score (SDS) of +9.52 (+2.34 to +9.2), compared to SDS -1.46 (-2.91 to +2.17) and -1.22 (-2.8 to +1.58) in Gr 2 and 3, respectively (P<0.001). IGF-1 SDS values were +3.28 (+2.05 to +6.1), and IGF-1 was less than twice the upper limit of normal in all patients in Gr 4. OGTT was performed in 51 of the 101 acromegalic patients. The nadir GH in these patients was 4.01 (0.2 to 46.7) in comparison with 0.2 (<0.05 to 0.6) in Gr 4 (P<0.001).


CONCLUSIONS
Elevated IGF-1 levels, alone, are sufficient to establish a diagnosis of acromegaly in the majority of clinically suspected cases. The OGTT may be useful to obtain corroborative evidence when there is modest elevation of IGF-1 with absent or equivocal clinical features.
Department of Endocrinology, Diabetes and Metabolism, Cleveland Clinic, Cleveland, Ohio, USA.
Sreevidya K
SK
Subbarayan
Maria
M
Fleseriu
Murray B
MB
Gordon
Jessica A
JA
Brzana
Laurence
L
Kennedy
Charles
C
Faiman
Betul A
BA
Hatipoglu
Richard A
RA
Prayson
Johnny B
JB
Delashaw
Robert J
RJ
Weil
Amir H
AH
Hamrahian
D000172:Acromegaly / Q000097:blood* / Q000175:diagnosis*; D000236:Adenoma / Q000097:blood; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism*; D016022:Case-Control Studies; D005260:Female; D005951:Glucose Tolerance Test; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000097:blood; D012189:Retrospective Studies; D055815:Young Adult
D015415:Biomarkers; D001786:Blood Glucose; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone