Prevalence, Clinical and Biochemical Spectrum, and Treatment Outcome of Acromegaly With Normal Basal GH at Diagnosis

Abstract

Abstract Context The term micromegaly has been used to describe a subset of patients who have elevated IGF-1 levels but apparently normal basal GH (bGH) concentrations and often a glucose-suppressed GH of <1 ng/mL. Objective To evaluate the prevalence, clinical spectrum, and therapeutic outcome of acromegaly with normal bGH at diagnosis. Design and Methods Retrospective analysis of a cohort of patients with acromegaly diagnosed and treated at a tertiary care center. Results A cohort of 528 patients with acromegaly was stratified according to bGH at diagnosis: group 1, <2 ng/mL, n = 16; group 2, 2 to 9.9 ng/mL, n = 202; group 3, 10 to 99 ng/mL, n = 294; and group 4, ≥100 ng/mL, n = 16. Patients in group 1 (normal bGH) constituted 3% of the total cohort and were significantly older and more likely to be male than patients in the other groups. The frequency of acromegalic symptoms, signs, and comorbidities was similar between the four patient groups. Patients in group 1 more often harbored microadenomas (75%) and had significantly lower median IGF-1 and postglucose GH levels. Surgical success rates were similar between patients from groups 1 (53.8%), 2 (54.1%), and 3 (36.9%), whereas only 13.3% of patients in group 4 achieved remission. Conclusion Normal bGH acromegaly is uncommon in real life. These patients have some distinctive features that argue against this being simply acromegaly in its early stages.