Can intra-operative GH measurement in acromegalic subjects predict completeness of surgery?

Results of trans-sphenoidal pituitary surgery, in terms of long-term cure, vary considerably between centres. Additional techniques, which can assist the neurosurgeon in deciding whether surgery is complete or not, might therefore be important. One such potential tool is the intra-operative measurement of GH and calculating the plasma half-life from the plasma samples obtained after the presumed complete resection of the adenoma.

GH half-life was calculated from 5-10 min plasma samples after adenomectomy in 20 patients. GH was measured with a sensitive and rapid IFMA, and the results could be reported within 30 min, but were not used in this study for per-operative decisions. Cure was defined by a glucose suppressed plasma GH concentration below 1 mU/l (0.38 microgram/l) during follow-up studies and a normal plasma IGFI concentration.

In 13 cured patients the plasma half-life was 22.2 +/- 1.9 min (range 14-40.6). In three non-cured patients the plasma half-life could not be calculated, and in four other patients the plasma half-life was 35.8 +/- 5.9 min (range 25.8-51 min). By applying 25 min as the upper normal limit for the GH plasma half-life, the sensitivity was 77%, specificity 100%, and positive predictive value 100%.

Per-operative plasma GH monitoring is a potentially useful tool for determining the completeness of trans-sphenoidal surgery in acromegaly.