IGF-I, IGFBP-3 and ALS generation test in Turner syndrome

Short Stature in Isodicentric Y Chromosome and Three Copies of the SHOX Gene: Clinical Report and Review of Literature

Short stature homeobox gene (SHOX) mutations and pseudoautosomal region 1 (PAR1) deletions encompassing SHOX are known causes of Léri-Weill dyschondrosteosis and isolated short stature, while 3 copies of SHOX in cases with triple sex chromosome constitution are responsible for tall stature. Duplications involving SHOX have been rarely reported, and they were found in individuals with short, normal and tall stature. An adopted boy with short stature, isodicentric Y chromosome and 3 copies of SHOX is described. Normal growth hormone (GH) secretion and insulin-like growth factor 1 (IGF1) increase during an IGF1 generation test were found, ruling out impaired GH-IGF1 axis. No other organic or psychiatric causes of impaired growth were found. GH treatment improved linear growth, as reported in children with SHOX haploinsufficiency. This new report and the review of literature support that SHOX duplication may cause short stature, especially in those children with duplications of the 5'SHOX regulatory elements. Chromosome analysis and detailed molecular characterization of the duplicated region should be warranted in individuals with SHOX duplications in order to investigate the presence of occult chromosome imbalance. Additional reports and follow-up till adult height are needed to give conclusions on long-term efficacy and safety of GH treatment in short children with SHOX duplication.

IGF-I generation test in prepubertal children with Noonan syndrome due to mutations in the PTPN11 gene

BACKGROUND

Short stature represents one of the main features of children with Noonan syndrome. The reason for impaired growth remains largely unknown.

OBJECTIVE

To assess GH and IGF1 secretion in children with Noonan syndrome.

PATIENTS

12 prepubertal children with Noonan syndrome due to mutations in the PTPN11 gene [7 males, 6 females; median age, years: 8.6 (range 5.1-13.4)] were studied; 12 prepubertal children with short stature (SS) [7 males, 5 females; median age, years: 8.1 (range 4.8-13.1)] served as the control group.

MEASUREMENTS

GH secretion after arginine stimulation test; IGF1 generation test by measurement of IGF1 levels before and after recombinant GH (rGH) administration (0.05 mg/kg/day for 4 days).

RESULTS

Baseline and stimulated peak values of GH were not significantly different between the two groups. At +120 minutes, GH levels remained significantly higher (p = 0.0121) in comparison with baseline values in children with Noonan syndrome. Baseline IGFI levels in patients and in SS controls were not significantly different, in contrast to values after the rGH generation test [205 ng/mL (interquartiles 138.2-252.5 ng/mL) and 284.5 ng/mL (interquartiles 172-476 ng/mL), respectively; p = 0.0248]. IGF1 values were significantly related to height (baseline: r = 773, p = 0.0320; peak: r = 0.591, p = 0.0428) in children with Noonan syndrome.

CONCLUSIONS

Blunted increase of IGF1 after the rGH generation test was present in children with Noonan syndrome due to mutations in the PTPN11 gene in comparison with SS children. This finding may be due to partial GH resistance in the former likely related to altered Ras-MAPK signaling pathway.

Endocrine diseases, perspectives and care in Turner syndrome

Turner syndrome is a frequent chromosome disorder in clinical practice. It is characterized by short stature, gonadal dysgenesia and multisystemic involvement, responsible for a high morbidity and reduced life expectancy. The aim of the present paper is to describe the endocrinopathies and major problems at different ages, and to present suggestion for follow-up care in these patients.

Diagnosis of endocrine disease: limitations of the IGF1 generation test in children with short stature

The IGF1 generation test (IGFGT) is often used during the assessment of suspected GH insensitivity (GHI). We report the results of a survey undertaken in 2010 to determine the use of IGFGT amongst members of the European Society for Paediatric Endocrinology to evaluate suspected GHI. The literature surrounding the usefulness and limitations of IGFGT are reviewed, and recommendations provided for its use. Of 112 paediatric endocrinologists from 30 countries who responded to the survey, 91 (81%) reported that they had used the IGFGT in the previous 2 years; >10 IGFGT protocols were used. The IGFGT impacted treatment decisions for 97% of the respondents and was a prerequisite for recombinant human IGF1 treatment for 45% of respondents. From a literature review, sensitivity of the IGFGT was evaluated as 77-91% in molecularly proven cases of GHI; specificity was ≤97%, depending on the protocol. The positive predictive value of the IGFGT is likely to be low, as the frequency of normality is predictably higher than that of abnormality in GH signalling. Given the limitations of the IGFGT in the most severe cases of GHI syndrome (GHIS), the ability of the IGFGT to detect less severe GHIS is doubtful. In a pragmatic approach, the IGFGT may not be useful for the diagnosis of GHIS.