Laboratory investigation of acromegaly: is basal or random GH > 0.4 µg/L in the presence of normal serum IGF-1 an important result?
OBJECTIVE
To determine the frequency of indication of the GH suppression test and pituitary magnetic resonance imaging (MRI) in patients with clinical suspicion of acromegaly with GH concentrations > 0.4 µg/L despite normal serum IGF-1.


METHODS
A total of 160 patients with clinical suspicion of acromegaly with normal IGF-1 were studied.


RESULTS
Basal GH > 0.4 µg/L was observed in 70/88 women (79.5%). Nadir GH > 0.4 µg/L was found in 21/70 women (30%) and these patients were submitted to MRI, which revealed a microadenoma in 2/21 women (9.5%). In these two women, IGF-1 continued to be normal in subsequent measurements and no clinical progression has been observed so far (time of follow-up until now 4 years). Basal GH > 0.4 µg/L was seen in 33/72 men (45.8%). Nadir GH was < 0.4 µg/L in all of them.


CONCLUSIONS
In patients with clinical suspicion of acromegaly, concern over GH concentration in the presence of normal IGF-1 results in the unwarranted complementary investigation in many cases, and even in possible equivocal diagnoses. It is only in exceptional cases that normal IGF-1 should not rule out acromegaly.
Santa Casa de Belo Horizonte, Belo Horizonte, MG, Brazil.
Pedro Weslley
PW
Rosario
Neuroendocrinology Department, Santa Casa de Belo Horizonte, Belo Horizonte, MG, Brazil.
Maria Regina
MR
Calsolari
D000172:Acromegaly / Q000097:blood / Q000175:diagnosis*; D000328:Adult; D000465:Algorithms; D015415:Biomarkers / Q000097:blood; D005260:Female; D005951:Glucose Tolerance Test; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010902:Pituitary Gland / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011877:Radionuclide Imaging; D012016:Reference Values; D011795:Surveys and Questionnaires
D015415:Biomarkers; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I