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

Objetivo: Evaluar 2 ensayos sensibles para la determinación de insulin-like growth factor 1 (IGF-1) y somatotropina (GH) tras la prueba de sobrecarga oral de glucosa (SOG) en controles sanos. Métodos: Se realizó una SOG con 75 g a 19 adultos sanos y se determinaron las concentraciones séricas de IGF-1 y GH. Las concentraciones de GH e IGF-1 se midieron mediante un ensayo inmunorradiométrico sensible (IRMA) y por un ensayo inmunométrico quimioluminiscente muy sensible (CLIA). Resultados: La concentración media de IGF-1 fue 153 ± 65 ng/ml medida por IRMA y 144 ± 56 ng/ml por CLIA. Las concentraciones medianas (rango intercuartílico) de GH basal por IRMA frente a CLIA fueron 0,8 (0,5-3) mg/l frente a 0,5 (0,1-2,4) mg/l. La mediana del nadir de GH medido por IRMA fue 0,4 (0,3-0,5) mg/l y 0,08 (0,01-0,22) mg/l con CLIA. Cuando en cada sujeto se calculó el cociente de GH basal IRMA/CLIA, se obtuvo una mediana del ratio en todo el grupo de 1,68. Igualmente, la mediana del ratio del nadir de GH IRMA/CLIA total fue 4,44. Uno de los sujetos no consiguió una supresión por debajo de los valores establecidos, con un nadir de GH de 1,2 mg/l por IRMA y 1 mg/l por CLIA, sobrepasando el punto de corte tradicional que define la presencia de acromegalia cuando el método de medida fue IRMA. Conclusiones: La evaluación del eje GH/IGF-1 debería realizarse con un ensayo inmunométrico quimioluminiscente muy sensible (CLIA). En nuestra opinión, no hay necesidad de rebajar el punto de corte en la supresión de GH para establecer el diagnóstico de acromegalia. No encontramos diferencias significativas en cuanto a sexo, IMC o edad respecto al nadir de GH, por lo que nuestros datos no apoyan la utilización de diferentes criterios para el cribado de acromegalia en varones y mujeres o en jóvenes y mayores (AU)

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 (AU)

Evaluation of two highly sensitive assays for serum IGF-1 and GH determination following oral glucose tolerance test in healthy controls.

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 75g 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±65ng/ml measured by IRMA and 144±56ng/ml measured by CLIA. The median (interquartile range) basal GH concentrations by IRMAvs CLIA were 0.8 (0.5-3) µg/l vs 0.5 (0.1-2.4) µg/l. The median nadir GH measured by IRMA in these subjects was 0.4 (0.3-0.5) µg/l, and the mean nadir GH by CLIA was 0.08 (0.01-0.22) µg/I. 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 µg/l by IRMA and 1 µg/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.