Laboratory assessment of GH

Dietary Supplementation with Flammulina velutipes Stem Waste on Growth Performance, Fecal Short Chain Fatty Acids and Serum Profile in Weaned Piglets

This study was conducted to evaluate the effects of dietary FVS supplementation on growth performance, nutrient digestibility, biochemical profile of serum and fecal short chain fatty acids (SCFAs) production in weaned piglets. In Exp.1, 150 weaned pigs (initial body weight: 6.89 ± 1.17 kg) were allotted to five dietary treatments. The treatment diets included a basal diet and four experimental diets supplemented with 2.5%, 5.0%, 7.5% and 10.0% FVS respectively. The animal trial lasted for 28 days. In Exp.2, 72 piglets (initial body weight: 8.20 ± 1.67 kg) were allotted to three dietary treatments. The treatment diets included a basal diet and two experimental diets supplemented with 1.5% and 3.0% FVS, respectively. The animal trial lasted for 56 days. The results showed that pigs fed dietary FVS with 3% or lower inclusion levels had no significant difference (p > 0.10) on growth performance compared with pigs fed the control diet during day 1-28 and day 1-56. Dietary FVS supplementation decreased the apparent total tract digestibility (ATTD) of nutrients on day 28, day 35 and day 56, but no significant changes (p > 0.05) of nutrient digestibility were observed on day 14. Although piglets fed diets with higher levels of FVS showed impaired growth performance and ATTD of nutrients, dietary FVS supplementation improved the fecal SCFA production, antioxidant capacity, interleukin-2 and growth hormone levels in serum, and reduced the harmful low-density lipoprotein levels in serum on day 56. In conclusion, as a promising alternative fibrous ingredient, FVS could be supplemented in diets of weaned piglets with a proportion under 3%.

Acromegaly clinical trial methodology impact on reported biochemical efficacy rates of somatostatin receptor ligand treatments: a meta-analysis

INTRODUCTION

Biochemical efficacy of somatostatin receptor ligand (SRL) treatment in acromegaly is defined by metrics for GH and IGF-1 control. Since the earliest therapeutic trials, biochemical control criteria, medical formulations, and assay techniques have evolved.

MATERIALS AND METHODS

We searched PubMed for English-language trials published from 1974 to 2012 evaluating 10 or more patients, with a duration of more than 3 months and biochemical control as a key objective. We used a random-effects model to compare biochemical outcomes for octreotide and lanreotide trials according to study design characteristics.

RESULTS

A total of 4464 patients were enrolled in the analyzed trials; 4125 were treated, and 3787 completed study treatment. Overall achieved control rates were 56% for mean GH and 55% for IGF-1 normalization. Treatment duration was significantly related to both GH (P < .001) and IGF-1 control (P = .02). Prior SRL therapy (P = .01), and year of study publication (P = .03) were related to biochemical control for GH but not IGF-1. No statistically significant differences in GH or IGF-1 response rates were observed for multicenter vs single center, retrospective vs prospective, study drug, and preselection for SRL responsiveness. Dosing scheme, GH response criterion, or switch study design were also not statistically significant in determining GH or IGF-1 response rate.

CONCLUSIONS

Clinical design characteristics anticipated to impart efficacy bias including switching, preselection for SRL responsiveness, and retrospective design had no statistically significant impact on efficacy determination. Later year of publication, study duration, and prior SRL use are significant efficacy determinants for acromegaly trial outcomes.

Variation in growth hormone immunoassays in clinical practice in Canada

BACKGROUND/AIMS

The diagnosis of growth hormone (GH) deficiency in children in Canada is based on clinical, auxological, radiographic and biochemical criteria which include response to provocative GH testing. The objective of this study was to determine the variability of GH assays used at Canadian pediatric hospitals.

METHODS

Pooled samples of patient sera were generated at a single center and tested at 15 laboratories across Canada using local GH assays. Additional samples were analyzed using the most commonly employed assays.

RESULTS

DSL and AutoDelfia) assays measured lower for all samples. Linear regression analysis demonstrated excellent correlation between Access 2), AutoDelfia, and Immulite 2000), however, Bland-Altman plots revealed bias when comparing these assays.

CONCLUSIONS

Adequate comparison and standardization of commercially available GH immunoassays is necessary to ensure consistent interpretation of results.

GH response to hypoglycemia and clonidine in the GH-releasing hormone resistance syndrome

GH secretion by the pituitary is the result of the balance between the stimulatory effect of GHRH and the inhibitory effect of SS. Patients with mutations in GHRH receptor (GHRH-R) gene (GHRH-R) offer a unique model to study the mechanism of action of different GH secretion stimuli. In the past, we have demonstrated a small but significant GH response to a GH secretagogue (GHRP-2) in a homogenous cohort of patients with severe GH deficiency (GHD) due to a homozygous null mutation in GHRH-R (IVS1+1G-->A). Now, we sought to determine if we could detect a GH response to hypoglycemia (ITT: insulin tolerance test) or clonidine (CL) in these patients. Nine young GHD subjects underwent both ITT and CL tests, and 2 additional subjects underwent only CL test. There was a small but significant GH increase during ITT, but not during CL test. These results indicate that a minimal albeit significant GH response to ITT can occur despite complete lack of GHRH-R function.

A brief review of the use and utility of growth hormone stimulation testing in the NCGS: do we need to do provocative GH testing?

True growth hormone deficiency (GHD) in childhood, while rare, has major clinical consequences. GHD is often associated with other pituitary hormone deficiencies, so these children may require multiple hormonal replacement and close clinical follow-up to optimize their outcome. Growth hormone stimulation testing (GHST), as currently conducted, is not a reliable diagnostic tool. Both changes in growth hormone assay methodologies and increases in the diagnostic threshold contribute to the incorrect labeling of a substantial proportion of normal children as having idiopathic GHD. Fortunately, newer imaging technologies and laboratory tests form a more rational basis to diagnose true GHD. The use of GHST among GH-naive subjects (<20 years of age) enrolled in the National Cooperative Growth Study has declined over the past two decades, from a high of 89% between 1987 and 1989 to only 52% in 2002. Given that GH stimulation testing does not meaningfully aid in distinguishing those few children with true growth hormone deficiency from the much more common short normal child and that alternatives are now available, it is time to discontinue the routine use of GHST in children.

Sensitivity and specificity of six tests for the diagnosis of adult GH deficiency

Although the use of the insulin tolerance test (ITT) for the diagnosis of adult GH deficiency is well established, diagnostic peak GH cut-points for other commonly used GH stimulation tests are less clearly established. Despite that fact, the majority of patients in the United States who are evaluated for GH deficiency do not undergo insulin tolerance testing. The aim of this study was to evaluate the relative utility of six different methods of testing for adult GH deficiency currently used in practice in the United States and to develop diagnostic cut-points for each of these tests. Thirty-nine patients (26 male, 13 female) with adult-onset hypothalamic-pituitary disease and multiple pituitary hormone deficiencies were studied in comparison with age-, sex-, estrogen status-, and body mass index-matched control subjects (n = 34; 20 male, 14 female). A third group of patients (n = 21) with adult-onset hypothalamic-pituitary disease and no more than one additional pituitary hormone deficiency was also studied. The primary end-point was peak serum GH response to five GH stimulation tests administered in random order at five separate visits: ITT, arginine (ARG), levodopa (L-DOPA), ARG plus L-DOPA, and ARG plus GHRH. Serum IGF-I concentrations were also measured on two occasions. For purposes of analysis, patients with multiple pituitary hormone deficiencies were assumed to be GH deficient. Three diagnostic cut-points were calculated for each test to provide optimal separation of multiple pituitary hormone deficient and control subjects according to three criteria: 1) to minimize misclassification of control subjects and deficient patients (balance between high sensitivity and high specificity); 2) to provide 95% sensitivity for GH deficiency; and 3) to provide 95% specificity for GH deficiency. The greatest diagnostic accuracy occurred with the ITT and the ARG plus GHRH test, although patients preferred the latter (P = 0.001). Using peak serum GH cut-points of 5.1 microg/liter for the ITT and 4.1 microg/liter for the ARG plus GHRH test, high sensitivity (96 and 95%, respectively) and specificity (92 and 91%, respectively) for GH deficiency were achieved. To obtain 95% specificity, the peak serum GH cut-points were lower at 3.3 microg/liter and 1.5 microg/liter for the ITT and ARG plus GHRH test, respectively. There was substantial overlap between patients and control subjects for the ARG plus L-DOPA, ARG, and L-DOPA tests, but test-specific cut-points could be defined for all three tests to provide 95% sensitivity for GH deficiency (peak GH cut-points: 1.5, 1.4 and 0.64 microg/liter, respectively). However, 95% specificity could be achieved with the ARG plus L-DOPA and ARG tests only with very low peak GH cut-points (0.25 and 0.21 microg/liter, respectively) and not at all with the L-DOPA test. Although serum IGF-I levels provided less diagnostic discrimination than all five GH stimulation tests, a value below 77.2 microg/liter was 95% specific for GH deficiency. In conclusion, the diagnosis of adult GH deficiency can be made without performing an ITT, provided that test-specific cut-points are used. The ARG plus GHRH test represents an excellent alternative to the ITT for the diagnosis of GH deficiency in adults.