Endocrine Abstracts

Introduction: Acromegaly is associated with multiple comorbidities and excess mortality. However, disease burden is reduced by maintaining IGF-1 (and/or GH) levels under safe levels. First generation long-acting SMSa, administered at monthly intervals, represent the first line medical treatment. According to guidelines, its efficacy is evaluated through IGF-I measurements. However, there are no data indicating the optimal time for measuring IGF-I levels after the SMSa injection, and if the interval between the injections and the blood sampling might have importance for assessing the disease control.

Aim: To determine in real life if the time when IGF-I is measured after SMSa injection provides a consistent and correct evaluation of disease control in order to improve understanding of patients’ response to chronic treatment and to set up a more pertinent follow-up program.

Methods: Retrospective analysis of four (to five) weekly blood sampling performed for IGF-I measurement in 35 patients (males, 49%; mean age, 60 ± 14 years) with acromegaly treated with long-acting SMSa (octreotide LAR, n = 9; lanreotide Autogel, n = 26) for a mean duration of 9.4 ± 8.9 years. Blood was sampled according to the following schedule: just before the SMSa injection and then one, two, three, and eventually four weeks after the injection (the fourth sampling being made just before the next injection). IGF-I was also measured weekly in six healthy controls (mean age, 40 ± 11 years) for four weeks. Data were analyzed through charts, t-test and repeated measures ANOVA test.

Results: According to IGF-I levels, acromegaly was considered as controlled in 58.8%, 73.5%, 71.9% and 64.7% of patients before injection, at the first, second and third week following the injection, respectively. Only 58.8% of patients had normal IGF-I during the entire follow-up. Repeated measures ANOVA test showed statistically significant difference between the four measures (P = 0.005). Reproducibility between IGF-I levels measured just before the injection (first sampling) and four weeks later, just before the next injection, was good (two-sided t-test, P = 0.29). IGF-I variability in uncontrolled patients was higher than that of healthy controls.

Conclusion: Our study highlights that evaluation of disease control in patients on long-acting SMSa may vary according to the time when IGF-I is measured after the injection. According to our study, a single random IGF-I measurement does not properly reflect monthly hormone profile in 41.2% of our patients. If IGF-I is measured one week after the injection more patients are considered as controlled than when IGF-I is measured later between monthly injections.