Growth hormone standardisation
The diagnosis of disorders of growth hormone (GH) secretion is based on the measurement of GH before and after dynamic tests. Over the years, specific cut-off values have been proposed without reference to the considerable variation in results due to different methods for analysing GH. These analytical factors were reported in a meeting held at the National Institute for Biological Standards and Control (NIBSC) in 2000. One of the conclusions was that the recombinant DNA derived standard (IS 98/574) should replace the pituitary derived standard IS 80/505.
The key issue with IS 80/505 is that it is defined in IU but has no assigned mass value. This has led to factors between 2 and 3 being used to convert mass to U. The lack of transparency in this conversion has clearly contributed to the confusion over definitions of GH deficiency.
The more recent IS 98/574 is a recombinant preparation with defined physico-chemical characteristics and an assigned value of 3.0 U/mg. This will enable reporting of GH results in μg/L or mU/L of IS 98/574; such that values expressed in μg/L will be one third of the same value expressed in mU/L.
In 2006, major clinical endocrinology journals advised submitting authors that they would only accept GH data submitted in μg/L of IS 98/574.
- Standardisation of human growth hormone (hGH) assays. http://www.birminghamquality.org.uk/DLopen/nibscgh.pdf accessed 17 July 2008
- Sheppard MC. Growth hormone assay standardization: an important clinical advance. Clin Endocrinol 2007;66:157–161.
- Wieringa, JH Barth, P Trainer. Growth hormone assay standardisation: a biased view? Clin Endocrinol 2004;60:538-539.
- Barth JH, Sibley PE. Standardisation of the IMMULITE systems Growth Hormone assay standardised with the recombinant IS 98/574. Ann Clin Biochem 2008; in press
JHB 17 July 2008