Do "so-called" normal growth hormone concentrations (2-5 micrograms/l) indicate cure in acromegaly?

The study was undertaken to determine whether acromegalic patients with mean growth hormone (GH) concentrations of 2-5 micrograms/l have biochemically active disease following pituitary surgery or radiotherapy. 22 patients with acromegaly, 22 post surgery, 19 post radiotherapy had GH concentrations estimated during: (i) an oral glucose tolerance test (OGTT), (ii) a standard TRH test and (iii) 20 minute sampling for 8 hours. IGF-1 concentrations were measured. 6 normal subjects were also studied. Patients were divided into 3 groups on the basis of their mean GH concentration during the 8 hour sampling, > 5 micrograms/l, 2-5 micrograms/l, < 2 micrograms/l. Patients with mean GH concentrations of 2-5 micrograms/l (n = 6) had biochemically active disease: all had inadequate suppression of GH after OGTT, 5 had elevated IGF-1 concentrations, 4 had a paradoxical response to TRH. Patients with mean GH concentrations > 5 micrograms/l (n = 6) all had inadequate suppression after OGTT, 5 of 6 had increased IGF-1 concentrations, and 5 had abnormal responses to TRH. Of patients with mean GH concentrations < 2 micrograms/l (n = 10), 2 had elevated IGF-1 levels, 5 had abnormal responses to TRH and 4 inadequate GH suppression after OGTT. GH pulse number was similar in the three groups and GH pulse amplitude was significantly higher in those with GH > 5 micrograms/l compared to the other groups. In conclusion patients with GH concentrations of 2-5 micrograms/l have biochemically active disease and should be considered for further therapy after hypophysectomy.