Decrease of Serum IGF-I following Transsphenoidal Pituitary Surgery for Acromegaly

• Published in: Clinical chemistry (Baltimore, Md.) Vol. 63; no. 2; pp. 486 - 494
• Main Authors: Yu, Min, Bruns, David E, Jane, Jr, John A, Nass, Ralf M, Oldfield, Edward H, Vance, Mary Lee, Thorner, Michael O
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-02-2017
• Subjects: Accuracy; Acromegaly - blood; Acromegaly - metabolism; Acromegaly - surgery; Female; Funding; Humans; Insulin-Like Growth Factor I - analysis; Insulin-Like Growth Factor I - metabolism; Laboratories; Male; Mass spectrometry; Medical records; Patients; Pituitary Neoplasms - blood; Pituitary Neoplasms - metabolism; Pituitary Neoplasms - surgery; Postoperative period; Scientific imaging; Studies; Surgery; Tumors
• ISSN: 0009-9147; 1530-8561
• DOI: 10.1373/clinchem.2016.262592

In the immediate postoperative period following resection of growth hormone (GH)-secreting pituitary tumors, serum concentrations of GH have limited ability to predict remission of acromegaly. Since many actions of GH actions are mediated by insulin-like growth factor-1 (IGF-I), we aimed to determine the rates of fall of IGF-I during 72 h after surgical resection of pituitary tumors.
We studied patients who were undergoing pituitary surgery for acromegaly. IGF-I was measured by LC-MS and GH by immunoassay. Remission was defined by the combination of serum GH <0.4 ng/mL during oral glucose tolerance testing performed 8 weeks after the surgical procedure and normal IGF-I at ≥8 weeks.
During the first 72 h after surgery, the mean (SD) rate of decline of IGF-I was 185 (61) ng/mL per 24 h in those who achieved remission (n = 23), with a mean (SD) apparent half-life of 55 (19) h. IGF-I had decreased to <65% of the preoperative IGF-I on postoperative day 2 in 20 of 23 remission patients (87%) vs none of 5 patients who did not achieve remission. GH was <2.7 ng/mL on day 2 in 21 of 23 remission patients (91%), but in none of the nonremission patients. The combination of IGF-I and GH on day 2 separated the remission and nonremission groups of patients.
Rapid decline of serum IGF-I during the immediate postoperative period warrants further study as an analytically independent adjunct to GH measurement for early prediction of biochemical remission of acromegaly.