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Endocrine Abstracts (2023) 93 OC11 | DOI: 10.1530/endoabs.93.OC11

1LMU Klinikum; Med. Klinik und Poliklinik IV / Endokrinologie; Med. Klinik und Poliklinik IV, Endokrinologisches Labor, Innenstadt, Munich, Germany; 2Med. Klinik & Poliklinik IV, LMU Klinikum, Medizinische Klinik und Poliklinik IV, München, Germany; 3Medizinische Klinik und Poliklinik IV, LMU Klinikum München, Endokrinologisches Labor, München, Germany; 4Klinikum der Universität München, Medizinische Klinik und Poliklinik IV, Ludwig Maximillians Universität München; Med. Klinik und Poliklinik IV / Endokrinologie; Medizinische Klinik und Poliklinik IV, Munich, Germany, München, Germany; 5Epidemiologie Medizinische Fakultät, LMU München, Helmholtz Zentrum München – Deutsches Forschungszentrum für Gesundheit und Umwelt, Germany; 6Helmholtz Zentrum München, GmbH Deutsches Forschungszentrum für Gesundheit und Umwelt, Germany; 7LMU Klinikum, Med. Klinik und Poliklinik IV / Endokrinologie, Med. Klinik und Poliklinik IV, Munich, Germany.

Background: Soluble alpha klotho (sαKL) is high in active acromegaly, normalizes after disease control, and therefore is suggested as a new biomarker for growth hormone (GH) excess. However, little is known about the impact of biological variables other than GH.

Methods: Serum sαKL (pg/ml) was measured by ELISA (IBL, Hamburg, Germany). We first evaluated pre-analytical stability, defined a reference interval for sαKL in healthy subjects (A: n=890), and compared the concentrations to those in patients with non-functional pituitary tumors (NFPA, B, n=18) or prolactinomas (C, n=66). Moreover, we evaluated the potential impact of various biological variables on sαKL.

Results: The assay for SαKL exhibits excellent intra/inter-assay CVs (<10%) and linearity (92–107%). Concentrations were not significantly affected by storage at room temperature for 72 hours, or by up to 4 freeze/thaw cycles (recovery>90%). The reference interval (2.5–97.5%) for sαKL is 152–1303 (A: median: 673(IQR: 543–846)). SαKL was not different in NFPA (P>0.05), but higher in prolactinoma (902(754–1228); A vs.C, P<0.0001). Compared to IGF-I and IGFBP 3, SαKL exhibited a weaker negative correlation with age, BMI, waist-hip-ratio and cholesterol (rs=−0.30, −0.13, −0.12, −0,16, respectively, P<0.05 for all). In contrast, a positive correlation was seen with glomerular filtration rate and IGF-I (rs=0.11, 0.31, respectively, P<0.001 for all). While IGF-I and IGFBP 3 correlated with fasting glucose, sαKL did not (P>0.05), and it did also not vary significantly during oGTT (P>0.05). Slight reductions in SαKL were observed after >12h of fasting, and in females on estrogen monotherapy (P<0.05).

Conclusion: We stablished a reference range for sαKL, a highly stable biomarker of GH action. It is less affected by many biological variables than IGF-I and IGFBP 3. However, our data suggest it decreases in conditions of hepatic GH-resistance (prolonged fasting, oral estrogen), and is slightly increased by prolactin, most likely due to its somatotropic activity.

Volume 93

ESE Young Endocrinologists and Scientists (EYES) 2023

European Society of Endocrinology 

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