Schweizer JROL, Schilbach K, Haenelt M, et al. - Since soluble alpha klotho (sαKL) has been linked to growth hormone (GH) action, however, systematic evaluation and comparison to traditional biomarkers in acromegaly are missing, researchers conducted this retrospective study at two academic centers to assess the potential of sαKL to aid classification of disease activity. Participants in the study were patients with acromegaly before surgery (A, n = 29), after surgery controlled, discordant or uncontrolled without (B1, B2, B3, n = 28, 11, 8) or with somatostatin analogue treatment (C1, C2, C3, n = 17,11, 5), non-functioning pituitary adenomas (n = 20) and healthy controls (n = 31). The findings support the use of sαKL as a biomarker for assessing disease activity in acromegaly. It shows a close connection with GH secretory status, large dynamic range and robustness towards biological confounders. Its measurement could be useful, particularly when GH and IGF-I give contradictory results.