Targeting either GH or IGF-I during somatostatin analogue treatment in patients with acromegaly: a randomized multicentre study

Context

Discordant GH and IGF-I values are frequent in acromegaly. The clinical significance and its dependence on treatment modality and of glucose-suppressed GH (GH_nadir) measurements remain uncertain.

Objective

To evaluate the effects of targeting either IGF-I or GH during somatostatin analogue (SA) treatment.

Patients and Methods

84 patients with controlled acromegaly after surgery (n = 23) or SA (n = 61) underwent a GH profile including an OGTT, at baseline and after 12 months. SA patients were randomized to monitoring according to either IGF-I (n = 33) or GH_nadir (n = 28). SA dose escalation was allowed at baseline and 6 months.

Main outcome measures

GH_nadir and IGF-I at baseline and 12 months, and disease-specific Quality of Life (QoL).

Results

IGF-I and fasting GH levels were comparable between the surgery and the SA group, whereas GH_nadir (µg/L) was lower in the surgery group (GH_nadir 0.7 ± 0.1 vs 0.3 ± 0.1, P < 0.01). SA dose increase was performed in 20 patients in the GH group and in 8 patients in the IGF-I group (P = 0.02), which increased the number of concordantly controlled patients (P = 0.01). QoL was only mildly affected at baseline in all groups and did not changed consistently during the study.

Conclusion

(1) Discordant values in terms of high GH levels are prevalent in SA patients and more so if applying glucose-suppressed GH_nadir; (2) targeting discordant levels of either GH or IGF-I translates into SA dose increase and improved biochemical control; (3) even though QoL was not improved in this study, we suggest biochemical assessment of disease activity to include glucose-suppressed GH_nadir also in SA patients.

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