Two hour mean GH is not superior to basal GH for the follow-up of acromegalic patients treated with Octreotide LAR ®

Abstract

Background GH secretion, in acromegaly, is characterized by increased basal levels, as well as by increased frequency and amplitude of pulses. Evaluation of disease activity during follow-up of treated patients is frequently done with mean GH levels, although there is no established protocol for sample collection. Objective Determine mean GH value of 5 blood samples collected 30 min apart for 2 consecutive hours in the follow-up of acromegalic patients treated with octreotide LAR. Methods Ninety-one GH curves of 44 patients (25 women) were evaluated as were the respective IGF-I values (basal). Normal IGF-I for age and sex was considered standard for control of disease activity. Correlations between basal and mean GH were studied as were correlations between both values and %IGF-I above the upper limit of reference values (%ULRV). Results Median age of the group was 45.5 years (range 28–73). Twenty-five patients (56.8%) had previous surgery and 7 (15.9%) had both surgery and radiotherapy. A positive correlation was found between mean and basal GH ( r = 0.953; p < 0.001). Both basal and mean GH were correlated to %ULRV ( r = 0.645 and 0.661; p < 0.001 for both). In only 3 of the 91 curves (3.3%) there were discordances between basal GH and IGF-I, however the latter was concordant with mean GH. In 3 other curves there was concordance between basal GH and IGF-I although the latter was discordant with mean GH. Conclusions There was no benefit to perform GH curves with the present protocol. It may be due to our established outpatient follow up protocol. The use of more complex protocols and the cost of multiple GH assays should be acknowledged, and probably reserved for patients with basal GH levels between 1 and 5 μg/L with discordant GH and IGF-I.