Reduction of the pituitary GH releasable pool in short children with GH neurosecretory dysfunction

The influence of pituitary volume on the growth response in growth hormone-treated children with growth hormone deficiency or idiopathic short stature

PURPOSE

Magnetic resonance imaging (MRI) can be used for assessing the morphology of the pituitary gland in children with short stature. The purposes of this study were: (1) to determine if pituitary volume (PV) can distinguish patients with growth hormone (GH) deficiency from those with idiopathic short stature (ISS), (2) to validate an association between PV and severity of GH deficiency, and (3) to compare PV between good and poor response groups in children with GH deficiency or ISS after 1 year of treatment.

METHODS

Data were collected from the medical records of 152 children with GH deficiency or ISS who underwent GH stimulation test, sella MRI, and GH treatment for at least 1 year. Estimated PVs were calculated using the formula of an ellipsoid. We compared the PVs in patients with GH deficiency with those of patients with ISS. In addition, we assessed the association between PV and severity of GH deficiency, and we assessed growth response after treatment.

RESULTS

No difference was observed in PV between patients with GH deficiency and those with ISS. The severity of the GH deficiency seemed to be associated with PV (P=0.082), and the height of the pituitary gland was associated with severity of GH deficiency (P<0.005). The PV in the good response group was less than that of the poor response group in patients with GH deficiency (P<0.005), and PV showed no association with responsiveness to GH treatment in patients with ISS (P=0.073).

CONCLUSION

The measurement of PV cannot be used for differential diagnosis between GH deficiency and ISS. In patients with GH deficiency, PV tended to be smaller as the severity of GH deficiency increased, but the difference was not significant. PV may be a good response predictor for GH treatment. Further studies, including a radiomics-based approach, will be helpful in elucidating the clinical implications of pituitary morphology in patients with short stature.

Molecular Genetics and Pathogenesis of the Floating Harbor Syndrome: Case Report of Long-Term Growth Hormone Treatment and a Literature Review

Introduction: Floating Harbor syndrome (FHS) is an extremely rare disorder, with slightly more than a hundred cases reported worldwide. FHS is caused by heterozygous mutations in the SRCAP gene; however, little is known about the pathogenesis of FHS or the effectiveness of its treatment.

Methods: Whole-exome sequencing (WES) was performed for the definitive molecular diagnosis of the disease. Identified variants were validated using Sanger sequencing. In addition, systematic literature and public data on genetic variation in SRCAP and the effects of growth hormone (GH) treatment was conducted.

Results: We herein report the first case of FHS in the Russian Federation. The male proband presented with most of the typical phenotypic features of FHS, including short stature, skeletal and facial features, delayed growth and bone age, high pitched voice, and intellectual impairment. The proband also had partial growth hormone deficiency. We report the history of treatment of the proband with GH, which resulted in modest improvement in growth prior to puberty. WES revealed a pathogenic c.7466C>G (p.Ser2489*) mutation in the last exon of the FHS-linked SRCAP gene. A systematic literature review and analysis of available genetic variation datasets highlighted an unusual distribution of pathogenic variants in SRCAP and confirmed the lack of pathogenicity for variants outside of exons 33 and 34. Finally, we suggested a new model of FHS pathogenesis which provides possible basis for the dominant negative nature of FHS-causing mutations and explains limited effects of GH treatment in FHS.

Conclusion: Our findings expand the number of reported FHS cases and provide new insights into disease genetics and the efficiency of GH therapy for FHS patients.

DNA methylation profile is a quantitative measure of biological aging in children

DNA methylation changes within the genome can be used to predict human age. However, the existing biological age prediction models based on DNA methylation are predominantly adult-oriented. We established a methylation-based age prediction model for children (9-212 months old) using data from 716 blood samples in 11 DNA methylation datasets. Our elastic net model includes 111 CpG sites, mostly in genes associated with development and aging. The model performed well and exhibited high precision, yielding a 98% correlation between the DNA methylation age and the chronological age, with an error of only 6.7 months. When we used the model to assess age acceleration in children based on their methylation data, we observed the following: first, the aging rate appears to be fastest in mid-childhood, and this acceleration is more pronounced in autistic children; second, lead exposure early in life increases the aging rate in boys, but not in girls; third, short-term recombinant human growth hormone treatment has little effect on the aging rate of children. Our child-specific methylation-based age prediction model can effectively detect epigenetic changes and health imbalances early in life. This may thus be a useful model for future studies of epigenetic interventions for age-related diseases.

Cranial irradiation and growth hormone neurosecretory dysfunction: a critical appraisal

CONTEXT

It has been suggested that radiation-induced GH neurosecretory dysfunction exists in children; however, the pathophysiology is poorly understood, and it is unknown if such a phenomenon exists in adult life.

STUDY SUBJECTS

Twenty-four-hour spontaneous GH secretion was studied by 20-min sampling both in the fed state (n = 16; six women) and the last 24 h of 33-h fast (n = 10; three women) in adult cancer survivors of normal GH status defined by two GH provocative tests, 13.1 +/- 1.6 (range, 3-28) yr after cranial irradiation (18-40 Gy) for nonpituitary brain tumors (n = 12) or leukemia (n = 4) in comparison with 30 (nine women) age- and body mass index-matched normal controls (fasting, 11 men and three women).

RESULTS

Using previously published diagnostic thresholds, all patients had stimulated peak GH responses in the normal range to both the insulin tolerance test and the combined GHRH plus arginine stimulation test, as well as normal individual mean profile GH levels during the fed and fasting states. However, gender-specific comparisons revealed marked reduction (by 40%) in the overall peak GH responses to both provocative tests but similar GH secretory profiles; no differences were seen in the pulsatile attributes of GH secretion (cluster analysis) or the profile absolute and mean GH levels in the fed state or when the hypothalamic-pituitary axis was stimulated by fasting.

CONCLUSIONS

Radiation-induced GH neurosecretory dysfunction either does not exist or is a very rare phenomenon in irradiated adult cancer survivors. The normality of physiological GH secretion in the context of reduced maximum somatotroph reserve suggests compensatory overdrive of the partially damaged somatotroph axis and constitutes a relative argument against somatotroph dysfunction being explained purely by hypothalamic damage with secondary atrophy due to GHRH deficiency. It is therefore possible that radiation in doses less than 40 Gy causes dual damage to both the pituitary and the hypothalamus.

Physiological and pathological growth hormone secretion

Growth hormone (GH) secretion is normally episodic, with discrete bursts of GH super-imposed on a minimal basal level of production. This pattern of GH production yields a dynamic state between a low baseline and intervening peaks, posing a challenge for the clinician attempting to understand the 'true GH status' in a specific patient. This pulsatile pattern is maintained throughout the day, but there are clear differences between different segments of the day, with approximately two-thirds of the total daily secretion produced at night. The dynamic nature of GH production has led many investigators to suggest that when evaluating short stature, parameters of spontaneous GH production be applied rather than the GH response to artificial stimulation. GH secretory patterns in healthy control populations are compared to those in patients with several conditions seen by the pediatric endocrinologist (classical GH deficiency, GH neurosecretory dysfunction, acute lymphoblastic leukemia, hypothyroidism, small for gestational age, Russell-Silver syndrome, constitutional delay of growth and puberty and Fanconi's anemia) and variables used for analysis of these patterns are described. Inferences made from comprehensive evaluations of the GH axis in Fanconi's anemia provide unique insight into general GH pathophysiology.

Growth hormone deficiency and related disorders: insights into causation, diagnosis, and treatment

Advances in molecular biology have led to the identification of mutations within several novel genes associated with the phenotype of isolated growth hormone deficiency, combined pituitary hormone deficiency, and syndromes such as septo-optic dysplasia. Progress has also been made in terms of the optimum diagnosis of disorders of stature and their treatment. The use of growth hormone for the treatment of adults with growth hormone deficiency and conditions such as Turner's syndrome, Prader-Willi syndrome, intrauterine growth restriction, and chronic renal failure has changed the practice of endocrinology, although cost-benefit implications remain to be established.

The GH-IGF-I axis in children with idiopathic short stature

Idiopathic short stature (ISS) is a term used for children in whom the etiology of the short stature is undefined. Investigations of the growth hormone (GH)-insulin-like growth factor I axis have revealed several molecular and endocrinological defects in ISS patients. Abnormalities of GH secretion and action, although not frequent, will help to categorize some children with ISS. Because most diagnostic methods remain crude, however, their modification might be necessary to identify more subtle and yet functionally significant abnormalities of this endocrine axis.

Short children with familial short stature show enhancement of somatotroph secretion but normal IGF-I levels

The aim of the present study was to evaluate the GH status in children with familial, idiopathic short stature (FSS). To this goal we evaluated the GH response to GHRH (1 microg/kg iv) + arginine (ARG) (0.5 g/kg iv) test which is one of the most potent and reproducible provocative tests of somatotroph secretion, in 67 children with FSS [50 boys and 17 girls, age 10.8+/-0.4 yr, pubertal stages I-III, height between -3.6 and -1.6 standard deviation score (SDS), target height <10 degrees centile, normality of both spontaneous and stimulated GH secretion as well as of IGF-I levels]. The results in FSS were compared with those in groups of children of normal height (NHC) (42 NHC, 35 boys and 7 girls, age 12.0+/-0.5 yr, pubertal stages I-III, height between -1.3 and 1.4 SDS, height velocity standard deviation score (HVSDS)>25 degrees centile, GH peak >20 microg/l after GHRH+ARG test, mean GH concentration [mGHc]>3 microg/l) and children with organic GH deficiency (GHD) (38 GHD, 29 boys and 9 girls, age 11.2+/-3.7 yr, pubertal stages I-III, height between -5.7 and -1.3 SDS, GH peak <20 microg/l after GHRH +ARG test, mGHc <3 mg/l). Basal IGF-I levels and mGHc were also evaluated in each group over 8 nocturnal hours. IGF-I levels in FSS (209.2+/-15.6 microg/l) were similar to those in NHC (237.2+/-17.2 microg/l) and both were higher (p<0.0001) than those in GHD (72.0+/-4.0 microg/l). The GH response to GHRH +ARG test in FSS (peak: 66.4+/-5.6 microg/l) was very marked and higher (p<0.01) than that in NHC (53.3+/-4.5 microg/l) which, in turn, was higher (p<0.01) than in GHD (8.2+/-0.8 microg/l). Similarly, the mGHc in FSS was higher than in NHC (6.7+/-0.5 microg/l vs 5.1+/-0.7 microg/l, p<0.05) which, in turn, was higher than in GHD (1.5+/-0.2 microg/l, p<0.0001). In conclusion, our present study demonstrates that short children with FSS show enhancement of both basal and stimulated GH secretion but normal IGF-I levels. These findings suggest that increased somatotroph function would be devoted to maintain normal IGF-I levels thus reflecting a slight impairment of peripheral GH sensitivity in FSS.

TSH secretory pattern and thyroid function in children with growth hormone neurosecretory dysfunction

We evaluated the TSH secretory pattern and free T4 in 10 prepubertal children with short stature, normal response to GH provocative tests, and reduced GH integrated concentration (IC-GH) (GH neurosecretory dysfunction). Although their nadir TSH, peak TSH, TSH surge, and free T4 were lower than those of 12 children with short stature and normal IC-GH, none of the differences reached statistical significance. Thus, our results suggest that children with low IC-GH (GH neurosecretory dysfunction) exhibit a TSH secretory pattern and thyroid function similar to those with normal IC-GH.

Short procedure of GHRH plus arginine test in clinical practice

Either in children or in adults, arginine (ARG) alone and combined with GHRH (GHRH+ARG) are reliable tests for the diagnosis of GH deficiency. The procedures of these tests generally include GH measurement every 15 min from baseline up to 90-120 min. Aim of our study was to verify if the procedure of these tests could be usefully shortened in clinical practice. To this goal we have studied 173 normally growing children and adolescents (C, 117 M and 56 F, age: 11.3 +/- 0.4 yr.) and 125 young and middle aged normal adults (A, 68 M and 57 F, age: 30.0 +/- 0.6 yr.). ARG alone test was performed by 81 C and 33 A (0.5 g/kg arginine, i.v., from 0 to +30 min, up to a maximum of 30 g) while GHRH (1 microg/kg i.v. bolus at 0 min) + ARG test was performed by 92 C and 92 A. After ARG alone, taking into account data from +15 to +105 min, GH values above the 3rd centile limit of arbitrary cut-off (7 or 10 microg/l in C and 5 microg/l in A) occurred in 85% or 64% and 94% subjects, respectively. After GHRH+ARG test, taking into account only data at +30, +45, +60 min GH values above the 3rd centile limit (20 microg/l in C and 16.5 microg/l in A) occurred in 99% of subjects in both groups. Taking into account only these 3 timing points, the percentage of GH peak above the third centile limits after ARG alone was never higher than 60% in C and 85% in A. In conclusion, this study shows that single GHRH+arginine test can be reliably performed in a shortened procedure which makes easier the clinical practice and further reduces costs.