The harmonisation of growth hormone measurements: taking the next steps.

For over 20 years differences in results of growth hormone (GH) measurement have been recognised as being significant enough to lead to misdiagnosis and inappropriate management of patients with GH-related disorders. Whilst issues of method standardisation, variable antibody specificity, use of different reporting units with different conversion factors, and interference from GH binding protein have been acknowledged as contributing to the discrepancies, inconsistent approaches to method harmonisation have hampered opportunities to enhance the evidence base for GH measurements. Amongst the first steps to be taken, international collaboratives recommended the universal adoption of the International Standard 98/547 and the reporting of results in mass units. Whilst inter-method variability may have improved over the last 10 years, clinically significant differences remain. A more recently recognised issue contributing to the discrepancies may be the differences in the matrix materials used by kit manufacturers to assign values to their calibrants. The establishment of an international harmonisation oversight group is recommended: its key roles to include identification of a commutable matrix reference material, assessing the clinical significance of assay interferents, the evaluation of liquid chromatography-mass spectrometry as a reference measurement procedure and the provision of acceptance criteria for the clinical application of GH methods.

Lipid profiles in untreated severe congenital isolated growth hormone deficiency through the lifespan.

OBJECTIVE: Growth hormone deficiency (GHD) is associated with adverse changes in lipid profile. However, changes in lipids through life in a homogeneous group of GHD subjects have not been defined. PATIENTS AND MEASUREMENTS: We examined lipid levels in a group of untreated severely GHD patients with a mutation in the GHRH receptor gene from a rural community in North-east Brazil. Lipid profiles in 15 GHD subjects [eight children and adolescents (one male), age (median [range]) 13.2 (5.4-19.9) years; seven adults (one male), age 47 (33-66) years] were compared with those in 29 indigenous controls from the same extended kindred [17 children and adolescents (six male), age 10.2 (5.3-18.4) years; 12 adults (eight male), age 54.5 (33-80) years]. All GHD subjects had a peak GH response of < 0.5 ng/ml in response to an insulin tolerance test and extremely reduced IGF-1 levels (median 5.5 ng/ml). Data were compared between cohorts and with an age- and sex-matched white American reference population. RESULTS: Abnormalities were confined to plasma total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels. More GHD children had levels of plasma TC and LDL-C above the 95th percentile for our reference population (3/8 and 4/7, respectively) compared to controls (0/17 and 1/15, respectively) (P < 0.05). In the adults, median TC and LDL-C levels were higher in the GHD than controls (P < 0.05) (6.3 vs. 4.1 mmol/l; 4.4 vs. 2.7 mmol/l, respectively). Median Z-scores, calculated using values from the reference population, were not different between GHD children and adults for both TC (+0.8 vs.+0.4) and LDL-C (+1.4 vs.+0.7). CONCLUSIONS: The lipid profile in children as well as in adults with very severe GHD is adversely modified. There would appear to be no significant worsening of the lipid abnormality with duration of GHD or achievement of adulthood.