Biochemical evaluation of disease activity after pituitary surgery in acromegaly:: a critical analysis of patients who spontaneously change disease status

Background The definition of biochemical cure in acromegaly involves both the normalization of IGF-1 and a glucose-suppressed GH level of < 1 ng/ml. These criteria were reached by several consensus meetings, although no evidence-based recommendations as to the optimal time to perform biochemical evaluations were made, nor was the fact that several patients may change biochemically upon long-term follow-up taken into consideration. Objectives To identify and characterize biochemical changes in the follow-up of acromegaly. Patients and methods One hundred and twenty-six acromegalic patients seen at a referral centre were followed prospectively (6-108 months) with regard to glucose-suppressed GH levels and IGF-1 concentrations. Results Eighty-nine patients did not change biochemical status, whereas in 37 (29.3%), one or more changes were identified, mostly during the first year. When glucose-suppressed GH values were discordant with the IGF-1 results, the likelihood of biochemical status modification was significantly greater than when such results were concordant [concordant 19.4%, discordant 57.6%, odds ratio (OR) = 5.6, 95% confidence interval (CI) = 2.3-13.3, P = 0.0001]. Among the changing patients, four out of the nine subjects initially considered as cured remained so at the last follow-up, whereas five became discordant; of the nine initially categorized as active, only three kept such a status at the last evaluation, whereas five became GH discordant and one achieved full biochemical criteria of cure; of 17 initially GH-discordant patients, seven remained so upon the last evaluation, whereas six became concordantly active and four concordantly cured. Conclusion A significant proportion of acromegalic patients change biochemical status upon long-term follow-up after surgery. Most of these changes occur within the first postoperative year and are more likely to take place if the initial GH postglucose and IGF-1 levels are discordant.