title: Evaluation of two highly sensitive assays for serum IGF-1 and GH determination following oral glucose tolerance test in healthy controls.
abstract: 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.
authors.affiliation: Servicio de Endocrinología, Metabolismo y Nutrición. Hospital Clínico San Carlos. Madrid. España.
authors.forename: Nuria
authors.initials: N
authors.lastname: García de la Torre
authors.forename: Alejandra
authors.initials: A
authors.lastname: Durán
authors.forename: Paz
authors.initials: P
authors.lastname: de Miguel
authors.forename: José
authors.initials: J
authors.lastname: Angel Díaz
authors.forename: Felipe
authors.initials: F
authors.lastname: Hervás
authors.forename: Montserrat
authors.initials: M
authors.lastname: Puente
authors.forename: Aniceto
authors.initials: A
authors.lastname: Charro