Background <p>Micromegaly is a term suggested to describe patients with clinical and biochemical evidence of acromegaly despite apparently normal GH secretion. However, its clinical characteristics including biochemical definition, treatment outcomes, and long-term prognosis remain incompletely understood. This study aimed to determine the prevalence of micromegaly and compare the demographic, clinical, biochemical, radiological, and long-term follow-up characteristics of patients with micromegaly and classical acromegaly.</p> Methods <p>A retrospective chart review was conducted in patients with acromegaly, who were diagnosed and subsequently followed up in Erciyes University Department of Endocrinology between January 2010 and September 2025. Micromegaly was defined on the basis of the finding of a baseline growth hormone (GH) &lt; 2 ng/mL and/or glucose-suppressed GH nadir &lt; 1 ng/mL, in addition to an IGF-1 level above the upper limit of normal in a patient with the classic symptoms and signs of the disease.</p> Results <p>Among 117 patients with acromegaly, 14 (12%) were classified as having micromegaly. No statistically significant differences were observed in the age at diagnosis, gender distribution, comorbidities and clinical symptoms between patients with acromegaly and micromegaly. The micromegaly group demonstrated a higher incidence of microadenoma, with a significantly smaller maximal tumor size compared to the acromegaly group. The rate of surgical intervention, the total number of operations, and the rate of additional medical treatment among patients with acromegaly were significantly higher than among patients with micromegaly. The biochemical control rate observed at 3 months postoperatively was higher in the micromegaly group, while the remission rate at the last visit was similar between the two groups.</p> Conclusion <p>Patients classified as having micromegaly according to the biochemical criteria applied in this study exhibited clinical manifestations and comorbidity profiles comparable to those of patients with classical acromegaly despite lower GH levels and smaller tumors. Sensitivity analyses using alternative biochemical definitions demonstrated a broadly consistent overall clinical pattern across the different classification approaches. These findings suggest that apparently low GH secretion does not necessarily indicate clinically mild disease. Prospective multicentre studies using standardized biochemical definitions are required to further clarify the biological basis and clinical significance of micromegaly.</p> Clinical trial number <p>Not applicable.</p>