Investigation of the criteria for assessing the outcome of treatment in acromegaly

The outcome of treatment in acromegaly is usually assessed by measuring plasma concentrations of growth hormone (GH)--either basal spontaneous levels or during hyperglycaemia. There is no consensus on how cure should be defined. Many studies have considered basal plasma growth hormone concentrations below 20 mU/l (10 ng/ml) as proof of cure, although some recent studies have applied lower values. At present a limit of 10 mU/l (5 ng/ml) seems to be accepted as evidence of cure. We have studied 28 acromegalic patients after transsphenoidal adenomectomy. Plasma GH concentrations (basal and during hyperglycaemia) as well as plasma somatomedin C (SMC) concentrations were measured and compared to the clinical symptoms. There was a close correlation between plasma GH and SMC concentrations (except when plasma GH levels were low) and between the clinical assessment and SMC concentrations. Very low plasma GH levels (less than 1 mU/l or 0.5 ng/ml) were associated with normal SMC values and clinical cure, high GH levels (greater than 10 mU/l or 5 ng/ml) with elevated SMC levels and persisting acromegaly. Moderately elevated plasma GH concentrations (1.9-9.6 mU/l) did not allow any conclusions on the outcome of treatment as assessed from SMC determinations and clinical evaluation. It is concluded that the usual criteria for cure in acromegaly may not be sufficiently strict.