Value of early post-operative growth hormone assessment in acromegaly surgery
Prasanna Rao-Balakrishna1, Catherine Lee2, Margaret Roberts2, Shashana Shalet1, Christine Gibson3, Frederick Wu3, JRE Davis3, Kanna Gnanalingham1 & Tara Kearney1
Surgery is the treatment of choice for GH secreting tumours. Recent papers suggest, early re-exploration of persistently active tumours may be beneficial. Endocrine assessment, to confirm cure, in the immediate post-operative period is difficult. We aimed to ascertain which test of GH excess performed post-operatively is a reliable predictor of longer term cure
Methods: 16 consecutive patients (8 males and 8 females: mean age 46.8±13 years) with active Acromegaly underwent endoscopic transphenoidal surgery. On the 3rd and 4th post-operative days a Growth Hormone Day Curve(GHDC) and an OGTT were performed. Cure was defined as a mean GH on GHDC <5 mU/l and a nadir value during OGTT of <2 mU/l. Surgical re-exploration was offered to those with persistent GH excess and MR evidence of residual tumor. All patients underwent re-assessment for cure at least 6 weeks post-operatively, using the same criterion.
Results: 8 of 16 (50%) were biochemically cured after the first operation. The mean day-curve results were 2.2±1.4 mU/l and 12±10 mU/l and the nadir levels in OGTT were 0.6±0.5 mU/l and 3.2±1 mU/l in cured and not cured, respectively. The GHDC and OGTT tests were concordant in only 56.25%. Four (25%) of the sixteen patients had borderline results of whom 3 were biochemically cured at 6 week followup. The remaining four (25%) underwent an early re-exploration and of these two attained biochemical cure, resulting in a total cure rate of 81.25%.
For patients deemed cured on immediate testing a 100% correlation was observed between the immediate post-surgical tests and those repeated later, irrespective of which test was used. However 75% those with borderline results (GHDC between 56 mU/l and OGTT nadir 23 mU/l) were cured by six weeks.
Conclusion: These results suggest that the GHDC and OGTT with GH levels can be used in the immediate post-operative period to ascertain longer term cure from Acromegaly.