A Critical Appraisal of Growth Hormone Therapy in Growth Hormone Deficiency and Turner Syndrome Patients in Turkey

Analysis of N15-rat growth hormone after incubation with rat subcutaneous tissue and immune cells using ultra-pressure chromatography-mass spectrometry

Therapeutic proteins (TPs) are exposed to various immune cells like macrophages and neutrophils, especially after subcutaneous (SC) administration. It is well known that the immune cells can generate reactive oxygen species (ROS) and this may lead to oxidation of TPs. The oxidation can occur in the SC tissue after SC administration, during distribution to the immune organs like lymph nodes and spleen, and even in the blood circulation. The oxidation can lead to alteration of their pharmacokinetics and efficacy. Therefore, it is important to study the oxidation of TPs in the biological matrices using ultra-pressure chromatography-mass spectrometry. Rat growth hormone (rGH) was selected as a test protein due to its similarity with human growth hormone (hGH), which is widely used for treatment of growth hormone deficiency. In this manuscript, we have summarized sample processing strategy and ultra-pressure chromatography-mass spectrometry methodology to identify rGH and its degradation products after ex-vivo incubation with rat SC tissue, and in vitro incubation with rat splenocytes and canine peripheral blood mononuclear cells (cPBMCs) as a model foreign host species. We did not observe oxidation of rGH in these biological matrices. This could be due to very minor yields of oxidation products, lack of sensitivity of the mass spectrometry method, loss of protein during sample processing, rapid turnover of oxidized protein or a combination of all factors.

Coexistence of Growth Hormone Deficiency and Pituitary Microadenoma in a Child with Unique Mosaic Turner Syndrome: A Case Report and Literature Review

Turner syndrome (TS) is a genetic disorder with phenotypic heterogeneity caused by the monosomy or structural abnormalities of the X chromosome, and it has a prevalence of about 1/2500 females live birth. The variable clinical features of TS include short stature, gonadal failure, and skeletal dysplasia. The association with growth hormone (GH) deficiency or other hypopituitarism in TS is extremely rare, with only a few case reports published in the literature. Here, we report the first case of a patient with mosaic TS with complete GH deficiency and pituitary microadenoma, and we include the literature review. During the work-up of the patient for severe short stature, three GH provocation tests revealed peak GH levels of less than 5 ng/mL, which was compatible with complete GH deficiency. Sella magnetic resonance imaging showed an 8 mm non-enhancing pituitary adenoma with mild superior displacement of the optic chiasm. Karyotyping revealed the presence of ring chromosome X and monosomy X (46,X,r(X)/45,X/46,X,psu dic r(X;X)), which indicated a mosaic TS. It is important to consider not only chromosome analyses in females with short stature, but also the possibility of the coexistence of complete GH deficiency accompanying pituitary lesions in TS. In conclusion, the present study reports the first case of GH deficiency and pituitary adenoma in a patient with rare mosaic TS, which extends the genotype-phenotype spectrum for TS.

Evaluation of the Final Adult Height and Its Determinants in Patients with Growth Hormone Deficiency: A Single-centre Experience from the South-Eastern Region of Turkey

OBJECTIVE

The aim was to determine the final adult height (FAH) achieved by recombinant human growth hormone (rhGH) treatment, the factors affecting FAH and the success of attaining the genetic potential.

METHODS

Data of 133 patients treated with rhGH therapy were reviewed retrospectively. Patients were grouped according to diagnosis, either isolated GH deficiency (IGHD) or multiple pituitary hormone deficiency (MPHD), and by sex, and pubertal status at the beginning of treatment.

RESULTS

The mean age of initiation of treatment was 12.3±2.18 years, and the mean duration of rhGH treatment was 3.65±1.5 years. The mean height standard deviation score (SDS) at diagnosis was -3.11±0.75 SD. All patients received a standardized GH dose of 0.033 mg/kg/day. Mean FAH-SDS was -1.8±0.77 and delta height-SDS (the change in height SDS between the beginning and end of treatment) was 1.28±0.94 SD. FAH-SDS was -1.79±0.86 SD in males; -1.82±0.64 in females (p=0.857); -1.94±0.71 at the beginning of treatment in pubertal patients and -1.68±0.81 in prepubertal patients (p=0.056); -1.84±0.89 in patients with IGHD and -0.47±0.2 in patients with MPHD (p˃0.05). In multiple regression analysis, First year delta height-SDS was the most predictive factor for both FAH-SDS and delta height-SDS.

CONCLUSION

The majority of our patients achieved a final height compatible with their genetic potential as well as population standards when treated with rhGH even having started at a relatively late age. First year delta height-SDS was a predictive factor for FAH.

Effect of Iron Oxide Nanoparticles on the Oxidation and Secondary Structure of Growth Hormone

Oxidation of therapeutic proteins (TPs) can lead to changes in their pharmacokinetics, biological activity and immunogenicity. Metal impurities such as iron are known to increase oxidation of TPs, but nanoparticulate metals have unique physical and chemical properties compared to the bulk material or free metal ions. Iron oxide nanoparticles (IONPs) may originate from equipment used in the manufacturing of TPs or from needles during injection. In this study, the impact of IONPs on oxidation of a model protein, rat growth hormone (rGH), was investigated under chemical stress. Hydrogen peroxide (H2O2)- and 2,2'-azobis (2-methylpropionamidine) dihydrochloride oxidized methionine residues of rGH, but unexpectedly, oxidation was suppressed in the presence of IONPs compared to a phosphate buffer control. Fourier transform infrared spectroscopy indicated splitting of the α-helical absorbance band in the presence of IONPs, whereas circular dichroism spectra showed a reduced α-helical contribution with increasing temperature for both rGH and rGH-IONP mixtures. The results collectively indicate that IONPs can increase the chemical stability of rGH by altering the kinetics and preference of amino acid residues that are oxidized, although the changes in protein secondary structure by IONPs may lead to alterations of physical stability.