Value of growth hormone treatment in Turner's syndrome

A highly sensitive, high-throughput assay for the detection of Turner syndrome

OBJECTIVE

Turner syndrome (TS) occurs when an X-chromosome is completely or partially deleted or when X-chromosomal mosaicism is present. Girls with TS benefit from early diagnosis and treatment with GH; however, many girls with TS are not detected until after 10 yr of age, resulting in delayed evaluation and treatment.

METHODS

We developed a high-throughput test for TS, based on a quantitative method of genotyping to detect X-chromosome abnormalities. This test uses pyrosequencing to quantitate relative allele strength (RAS) from single-nucleotide polymorphisms using 18 informative single-nucleotide polymorphisms markers that span the X-chromosome and one marker for the detection of Y-chromosome material.

RESULTS

Cutoff ranges for heterozygous, homozygous, or out-of-range RAS values were established from a cohort of 496 males and females. Positive TS scoring criteria were defined as the presence of homozygosity for all 18 markers or the presence of at least one out-of-range RAS value. To determine the validity of this rapid test for TS detection, we undertook a large-scale study using DNA from 132 females without TS and 74 females with TS for whom karyotypes were available. TS was identified with 96.0% sensitivity and 97.0% specificity in this cohort. We also tested buccal swab DNA from a group of 19 females without TS and 69 females with TS. In this group, TS was identified with 97.1% sensitivity and 84.2% specificity.

CONCLUSIONS

These results demonstrate the validity of a high-throughput, pyrosequencing based test for the accurate detection of TS, providing a potential alternative to karyotype testing.

Efficacy and safety of Valtropin in the treatment of short stature in girls with Turner's syndrome

Valtropin (somatropin, BioPartners and LG Life Sciences [LGLS]) is a recombinant human growth hormone (GH) preparation produced using a yeast expression system. An open single-arm phase III study was conducted to evaluate efficacy and safety at a dose of 0.16 IU/kg/day (0.053 mg/kg/day) s.c. for 12 months in the treatment of short stature in girls (n = 30, aged 2-9 years) with Turner's syndrome. The primary efficacy variable was height velocity (HV) at 12 months. Secondary efficacy variables included serum GH dependent growth factors. HV increased from 3.8 +/- 1.8 cm/yr at baseline to 9.7 +/- 1.6 cm/yr (mean +/- SD) after 12 months of treatment. Marked treatment effects were also observed on other growth parameters, serum insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3). Treatment was well tolerated with no significant adverse events. It is concluded that Valtropin is as safe and effective as other human GH preparations for the treatment of growth failure in girls with Turner's syndrome.