Evaluación de dos inmunoensayos altamente sensibles para la determinación de IGF-1 y GH séricas tras sobrecarga oral de glucosa en controles sanos
Evaluation of two highly sensitive assays for serum IGF-1 and GH determination following oral glucose tolerance test in healthy controls
NURIA GARCÍA DE LA TORRE a, ALEJANDRA DURÁN a, PAZ DE MIGUEL a, JOSÉ ÁNGEL DÍAZ a, FELIPE HERVÁS a, MONTSERRAT PUENTE a, ANICETO CHARRO a
a Servicio de Endocrinología, Metabolismo y Nutrición. Hospital Clínico San Carlos. Madrid. España.
Palabras ClaveEnsayo inmunométrico quimioluminiscente. Ensayo inmunorradiométrico. Somatotropina. Insulin-like growth factor 1. Sobrecarga oral de glucosa. Acromegalia.
KeywordsChemiluminescent immunometric assay. Immunoradiometric assay. Growth hormone. Insulin-growth factor 1. Oral glucose tolerance test. Acromegaly.
Resum Objective: To evaluate 2 highly sensitive assays for serum insulin-like growth factor-1 (IGF-1) and growth hormone (GH) determination following an oral glucose tolerance test (OGTT) in healthy controls. Methods: Nineteen healthy adults underwent a standard 75 g OGTT and GH and IGF-1 were measured. Serum GH and IGF-1 levels were assayed by a sensitive immunoradiometric assay (IRMA) and a highly sensitive chemiluminescent immunometric assay (CLIA). Results: The mean IGF-1 concentration was 153 ± 65 ng/ml measured by IRMA and 144 ± 56 ng/ml measured by CLIA. The median (interquartile range) basal GH concentrations by IRMA vs CLIA were 0.8 (0.5-3) mg/l vs 0.5 (0.1-2.4) mg/l. The median nadir GH measured by IRMA in these subjects was 0.4 (0.3-0.5) mg/l, and the mean nadir GH by CLIA was 0.08 (0.01-0.22) mg/l. When a ratio of basal IRMA/CLIA GH was calculated in each subject, the median ratio of basal IRMA/CLIA GH concentrations in subjects overall was 1.68. Similarly, the median ratio of nadir IRMA/CLIA GH values was 4.44. One of the subjects did not achieve GH suppression into the established normal range, with a GH nadir of 1.2 mg/l by IRMA and 1 mg/l by CLIA, overlapping with the traditional cut-off defining acromegaly when GH suppression was measured by IRMA. Conclusions: Highly sensitive chemiluminescent immunometric assays should be used to assess the GH/IGF-1 axis. In our opinion, there is no need for a lower GH suppression cut-off for diagnosing acromegaly. We found no significant gender-, BMI- or age-related differences in nadir GH levels and thus our results do not support different OGTT criteria for screening of acromegaly in men and women, or in younger and older subjects.