Magnetic resonance imaging of the hypothalamus-pituitary unit in childrensuspected of hypopituitarism: who, how and when toinvestigate

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.

Preliminary study of longitudinal changes in the pituitary and brain of children on growth hormone therapy

BACKGROUND

In subjects with isolated growth hormone deficiency (IGHD), recombinant human growth hormone (rhGH) is an approved method to achieve potential mid-parental height. However, data reporting rhGH treatment response in terms of brain structure volumes were scarce. We report the volumetric changes of the pituitary gland, basal ganglia, corpus callosum, thalamus, hippocampus and amygdala in these subjects post rhGH treatment.

MATERIALS AND METHODS

This was a longitudinal study of eight IGHD subjects (2 males, 6 females) with a mean age of 11.1 ± 0.8 years and age-matched control groups. The pituitary gland, basal ganglia and limbic structures volumes were obtained using 3T MRI voxel-based morphology. The left-hand bone age was assessed using the Tanner-Whitehouse method. Follow-up imaging was performed after an average of 1.8 ± 0.4 years on rhGH.

RESULTS

Subjects with IGHD had a smaller mean volume of the pituitary gland, right thalamus, hippocampus, and amygdala than the controls. After rhGH therapy, these volumes normalized to the age-matched controls. Corpus callosum of IGHD subjects had a larger mean volume than the controls and did not show much volume changes in response to rhGH therapy. There were changes towards normalization of bone age deficit of IGHD in response to rhGH therapy.

CONCLUSION

The pituitary gland, hippocampus, and amygdala volumes in IGHD subjects were smaller than age-matched controls and showed the most response to rhGH therapy. Semi-automated volumetric assessment of pituitary gland, hippocampus, and amygdala using MRI may provide an objective assessment of response to rhGH therapy.

Pituitary gland volumes in children with normal endocrine function

BACKGROUND

Magnetic resonance imaging (MRI) is often the first modality of choice in the detection of pituitary pathologies due to its excellent contrast resolution and high spatial resolution. However, evaluating the size of the pituitary gland is somewhat difficult since the gland morphology varies widely among individuals.

OBJECTIVE

The aim of this study was to provide normal reference values for pituitary volumes in the pediatric population using three-dimensional (3-D) MRI data. We also aimed to compare the volumetric data measured through 3-D images with the mathematical volumes obtained by the ellipsoid formula from 2-D images, considering the demographic subgroups of age and sex.

MATERIALS AND METHODS

This study was performed retrospectively using PACS-archived brain MRIs obtained in the Pediatric Radiology Unit. Eight hundred children under the age of 18 who underwent brain MRI between January 2014 and May 2018 for headaches, seizures or trauma and who had no brain anomaly or endocrine pathology were recruited. Pituitary volumes were separately calculated from those brain MRIs by means of ellipsoid formula and volumetry. The mean, standard deviation, maximum and minimum and median values were achieved for each 1-year age group in both sexes. Normal reference ranges containing 5th -10th -25th -50th -75th -90th -95th percentiles of volumetric pituitary values were tabulated.

RESULTS

Pituitary gland volumes in both sexes were found to increase gradually with age. The average 3-D volume values were greater in girls than boys except for the age groups 1-2 years and 8-9 years. Pituitary volumes showed a growth spurt during early puberty, which was more prominent in girls. Moreover, a strong positive correlation was noted between the 2-D calculated and 3-D measured volumes in both sexes.

CONCLUSION

Normative data obtained through this study can be used for clinical diagnostic purposes as well as a reference for future research. The 2-D calculated volumes be used where it is not possible to obtain 3-D volumetric values.

A Radiomics-Based Model with the Potential to Differentiate Growth Hormone Deficiency and Idiopathic Short Stature on Sella MRI

PURPOSE

We hypothesized that a radiomics approach could be employed to classify children with growth hormone deficiency (GHD) and idiopathic short stature (ISS) on sella magnetic resonance imaging (MRI). Accordingly, we aimed to develop a radiomics prediction model for differentiating GHD from ISS and to evaluate the diagnostic performance thereof.

MATERIALS AND METHODS

Short stature pediatric patients diagnosed with GHD or ISS from March 2011 to July 2020 at our institution were recruited. We enrolled 312 patients (GHD 210, ISS 102) with normal sella MRI and temporally split them into training and test sets (7:3). Pituitary glands were semi-automatically segmented, and 110 radiomic features were extracted from the coronal T2-weighted images. Feature selection and model development were conducted by applying mutual information (MI) and a light gradient boosting machine, respectively. After training, the model's performance was validated in the test set. We calculated mean absolute Shapley values for each of the selected input features using the Shapley additive explanations (SHAP) algorithm. Volumetric comparison was performed for GHD and ISS groups.

RESULTS

Ten radiomic features were selected by MI. The receiver operating characteristics curve of the developed model in the test set was 0.705, with an accuracy of 70.6%. When analyzing SHAP plots, root mean squared values had the highest impact in the model, followed by various texture features. In volumetric analysis, sagittal height showed a significant difference between GHD and ISS groups.

CONCLUSION

Radiomic analysis of sella MRI may be able to differentiate between GHD and ISS in clinical practice for short-statured children.

Pituitary stalk interruption syndrome

Pituitary stalk interruption syndrome (PSIS) is a distinct developmental defect of the pituitary gland identified by magnetic resonance imaging and characterized by a thin, interrupted, attenuated or absent pituitary stalk, hypoplasia or aplasia of the adenohypophysis, and an ectopic posterior pituitary. The precise etiology of PSIS still remains elusive or incompletely confirmed in most cases. Adverse perinatal events, including breech delivery and hypoxia, were initially proposed as the underlying mechanism affecting the hypothalamic-pituitary axis. Nevertheless, recent findings have uncovered a wide variety of PSIS-associated molecular defects in genes involved in pituitary development, holoprosencephaly (HPE), neural development, and other important cellular processes such as cilia function. The application of whole exome sequencing (WES) in relatively large cohorts has identified an expanded pool of potential candidate genes, mostly related to the Wnt, Notch, and sonic hedgehog signaling pathways that regulate pituitary growth and development during embryogenesis. Importantly, WES has revealed coexisting pathogenic variants in a significant number of patients; therefore, pointing to a multigenic origin and inheritance pattern of PSIS. The disorder is characterized by inter- and intrafamilial variability and incomplete or variable penetrance. Overall, PSIS is currently viewed as a mild form of an expanded HPE spectrum. The wide and complex clinical manifestations include evolving pituitary hormone deficiencies (with variable timing of onset and progression) and extrapituitary malformations. Severe and life-threatening symptomatology is observed in a subset of patients with complete pituitary hormone deficiency during the neonatal period. Nevertheless, most patients are referred later in childhood for growth retardation. Prompt and appropriate hormone substitution therapy constitutes the cornerstone of treatment. Further studies are needed to uncover the etiopathogenesis of PSIS.

The Molecular Basis of Congenital Hypopituitarism and Related Disorders

CONTEXT

Congenital hypopituitarism (CH) is characterized by the presence of deficiencies in one or more of the 6 anterior pituitary (AP) hormones secreted from the 5 different specialized cell types of the AP. During human embryogenesis, hypothalamo-pituitary (HP) development is controlled by a complex spatio-temporal genetic cascade of transcription factors and signaling molecules within the hypothalamus and Rathke's pouch, the primordium of the AP.

EVIDENCE ACQUISITION

This mini-review discusses the genes and pathways involved in HP development and how mutations of these give rise to CH. This may present in the neonatal period or later on in childhood and may be associated with craniofacial midline structural abnormalities such as cleft lip/palate, visual impairment due to eye abnormalities such as optic nerve hypoplasia (ONH) and microphthalmia or anophthalmia, or midline forebrain neuroradiological defects including agenesis of the septum pellucidum or corpus callosum or the more severe holoprosencephaly.

EVIDENCE SYNTHESIS

Mutations give rise to an array of highly variable disorders ranging in severity. There are many known causative genes in HP developmental pathways that are routinely screened in CH patients; however, over the last 5 years this list has rapidly increased due to the identification of variants in new genes and pathways of interest by next-generation sequencing.

CONCLUSION

The majority of patients with these disorders do not have an identified molecular basis, often making management challenging. This mini-review aims to guide clinicians in making a genetic diagnosis based on patient phenotype, which in turn may impact on clinical management.

Endocrine morbidity in midline brain defects: Differences between septo-optic dysplasia and related disorders

BACKGROUND

Septo-optic dysplasia (SOD) is a heterogeneous congenital condition. The aim of this study was to investigate the clinical phenotypes of a large cohort of children with SOD, Multiple Pituitary Hormone Deficiency (MPHD) and Optic Nerve Hypoplasia (ONH), with a focus on endocrine testing.

METHODS

Retrospective single-centre longitudinal study of children with SOD (n:171), MPHD (n:53) and ONH (n:35). SOD+ and SOD- indicate patients with or without hypopituitarism, respectively.

FINDINGS

All deficits were more frequent and occurred earlier in MPHD than SOD+ [Hazard Ratios (HR): 0·63(0·45,0·89) for GH, 0·48(0·34,0·69) for TSH, 0·55(0·38,0·80) for ACTH, 0·28(0·11,0·68) for gonadotropins], except Diabetes Insipidus (DI) [HR: 2·27(0·88,5·9)]. Severe hypothalamo-pituitary (H-P) abnormalities were more frequent in MPHD [80·0% vs 41·6%, p<0·0001 for Ectopic Posterior Pituitary (EPP)]. Stalk and PP abnormalities were associated with more severe endocrine phenotypes and placed a subgroup of SOD+ at risk of developing deficits earlier. SOD and ONH shared heterogeneous phenotypes ranging from pubertal delay to precocity and from leanness to extreme obesity, whilst MPHD had GnD and obesity only. Mortality was recorded in 4·2% (6/144) SOD and 3·2% (1/31) ONH, and only in patients with multisystem phenotypes.

INTERPRETATION

More than a single disease, SOD represents a spectrum of malformative conditions involving different brain structures and characterised by a dynamic and sequential nature of endocrine. In contrast, MPHD displays a more homogeneous phenotype of (mainly) anterior pituitary early-onset failure. Stalk and PP abnormalities place a subgroup of SOD+ at a higher risk of early-onset deficits. Additionally, there are striking differences between the SOD and MPHD cohorts in terms of pubertal progression. The shared phenotypes between ONH and SOD could be partly explained by common hypothalamic dysfunction. The differences between the cohorts are important as they may aid in planning management and preventing morbidity by dictating earlier interventions.

FUNDING

M.C., M.G., and N.I. were supported by the European Society of Paediatric Endocrinology (ESPE) through ESPE Clinical Fellowships.

Growth Hormone (GH) Therapy During the Transition Period: Should We Think About Early Retesting in Patients with Idiopathic and Isolated GH Deficiency?

To investigate growth hormone (GH) secretion at the transition age, retesting of all subjects who have undergone GH replacement therapy is recommended when linear growth and pubertal development are complete to distinguish between transitional and persistent GH deficiency (GHD). Early retesting of children with idiopathic and isolated GHD (i.e., before the achievement of final height and/or the adult pubertal stage) can avoid possible over-treatment. Here, we report data from our population with idiopathic and isolated GHD to encourage changes in the management and timing of retesting. We recruited 31 patients (19 males) with idiopathic GHD who received recombinant GH (rGH) for at least 2 years. All of the patients were retested at the transition age at least 3 months after rGH discontinuation. Permanent GHD was defined as a GH peak of <19 ng/mL after administration of growth hormone–releasing hormone (GHRH) + arginine as a provocative test. Permanent GHD was confirmed in only five of 31 patients (16.13%). None of these patients presented low serum insulin-like growth factor (IGF)-1 levels (<−2 standard deviation score (SDS)). Only one male patient with an IGF-1 serum level lower than −2 SDS showed a normal GH stimulation response, with a GH peak of 44.99 ng/mL. Few patients with idiopathic and isolated GHD demonstrated persistence of the deficit when retested at the transition age, suggesting that the timing of retesting should be anticipated to avoid overtreatment.

Pituitary height at magnetic resonance imaging in pediatric isolated growth hormone deficiency

BACKGROUND

Magnetic resonance imaging (MRI) is used for neuroradiologic evaluation of patients with idiopathic growth hormone deficiency (IGHD).

OBJECTIVES

To compare pituitary height and morphology at MRI between patients with IGHD and controls.

MATERIALS AND METHODS

This retrospective study was conducted in pediatric patients, 3 years-15 years old, who had had brain MRI with non-contrast-enhanced midsagittal T1-weighted images. These images were measured for pituitary height and morphology of the pituitary gland including shape, stalk and posterior pituitary bright spot was evaluated.

RESULTS

One hundred and nineteen patients were included, with 49 and 70 patients assigned to the study and control groups, respectively. Mean pituitary height was significantly less in the IGHD group than in the control group (3.81 mm±1.38 vs. 4.92 mm±1.13, retrospectively; P<0.001). Subgroup analysis revealed a significant difference in the pituitary height between groups in the prepubertal (8-10 years) and pubertal (11-13 years) periods (P=0.039 and P=0.006, respectively) and a trend toward significance in the postpubertal period (P=0.053). There was a significant difference in pituitary shape between IGHD and controls when combining grades III, IV and V (P=0.007). Other abnormal MRI findings of the pituitary stalk and posterior bright spot were significantly more often observed in the IGHD group (P<0.05).

CONCLUSION

Pituitary height was significantly smaller in patients with IGHD than in controls during prepuberty and puberty. Abnormal concave superior contour, hypoplastic stalk and absent/ectopic posterior bright spot were observed significantly more often among patients with IGHD.

Classical and non-classical causes of GH deficiency in the paediatric age

Growth hormone deficiency (GHD) may result from a failure of hypothalamic GHRH production or release, from congenital disorders of pituitary development, or from central nervous system insults including tumors, surgery, trauma, radiation or infiltration from inflammatory diseases. Idiopathic, isolated GHD is the most common sporadic form of hypopituitarism. GHD may also occur in combination with other pituitary hormone deficiencies, and is often referred to as hypopituitarism, combined pituitary hormone deficiency (CPHD), multiple pituitary hormone deficiency (MPHD) or panhypopituitarism. Children without any identifiable cause of their GHD are commonly labeled as having idiopathic hypopituitarism. MRI imaging is the technique of choice in the diagnosis of children with hypopituitarism. Marked differences in MRI pituitary gland morphology suggest different etiologies of GHD and different prognoses. Pituitary stalk agenesis and ectopic posterior pituitary (EPP) are specific markers of permanent GHD, and patients with these MRI findings show a different clinical and endocrine outcome compared to those with normal pituitary anatomy or hypoplastic pituitary alone. Furthermore, the classic triad of ectopic posterior pituitary gland, pituitary stalk hypoplasia/agenesis, and anterior pituitary gland hypoplasia is generally associated with permanent GHD. T2 DRIVE images aid in the identification of pituitary stalk without the use of contrast medium administration. Future developments in imaging techniques will undoubtedly reveal additional insights. Mutations in a number of genes encoding transcription factors - such as HESX1, SOX2, SOX3, LHX3, LHX4, PROP1, POU1F1, PITX, GLI3, GLI2, OTX2, ARNT2, IGSF1, FGF8, FGFR1, PROKR2, PROK2, CHD7, WDR11, NFKB2, PAX6, TCF7L1, IFT72, GPR161 and CDON - have been associated with pituitary dysfunction and abnormal pituitary gland development; the correlation of genetic mutations to endocrine and MRI phenotypes has improved our knowledge of pituitary development and management of patients with hypopituitarism, both in terms of possible genetic counseling, and of early diagnosis of evolving anterior pituitary hormone deficiencies.

High Frequency of Normal Response during GH Stimulation Tests in Patients with Ectopic Posterior Pituitary Gland: A Source of False-Negative Diagnosis of Pituitary Insufficiency

AIMS

To report false-negative normal growth hormone (GH) peak response in patients with ectopic posterior pituitary gland (EPP) identified with a simplified magnetic resonance imaging (FAST1-MRI).

METHODS

We analyzed 75 EPP patients with short stature and reduced growth velocity. Sagittal-T1 imaging (thickness: 2 mm and gap: 0.2 mm) without gadolinium administration was used. A GH peak of ≥5 ng/ml after clonidine or insulin stimulation was considered normal.

RESULTS

Normal GH response was observed in 15 of 75 (20%) patients [mean (SDS) peak = 8.2 (4.1) ng/ml]. Age at diagnosis [6.5 (3.0) years vs. 7.8 (4.1) years], gender (10 males/5 females vs. 44 males/16 females), pubertal stage (14 prepubertal/1 pubertal vs. 51 prepubertal/7 pubertal), and target height [-0.4 (0.6) vs. -0.4 (0.9)] were recorded. The perinatal history did not differ between responsive and nonresponsive patients. There was a trend to more frequent multiple hormone deficiency in nonresponsive when compared with responsive patients [3/15 (20%) and 31/60 (51.7%), respectively (p = 0.055)]. Height at diagnosis was lower in nonresponsive patients (p = 0.042). No significant difference in the IGF1 levels (p = 0.598) was observed between the groups.

CONCLUSION

Normal GH values after stimulation tests do not exclude EPP-associated GH deficiency. A simplified fast acquisition sagittal-T1 MRI protocol investigation included at the initial diagnostic approach is able to prevent misdiagnosis of GH deficiency in patients with short stature.

Development of additional pituitary hormone deficiencies in pediatric patients originally diagnosed with isolated growth hormone deficiency due to organic causes

OBJECTIVE

To determine characteristics of children initially diagnosed with isolated growth hormone deficiency (IGHD) of organic aetiology, who later developed multiple pituitary hormone deficiencies (MPHD).

DESIGN

Data were analysed for 716 growth hormone-treated children with organic IGHD, who were growth hormone-naïve at baseline in the multinational, observational Genetics and Neuroendocrinology of Short Stature International Study.

METHODS

Development of MPHD was ascertained from investigator-provided diagnoses, adverse events and concomitant medications. Analyses were performed for all patients and separately for those who developed MPHD within 4.5 years or had >3.5 years follow-up and continued to have IGHD (4-year cohort).

RESULTS

MPHD developed in 71/716 (9.9%) children overall, and in 60/290 (20.7%) in the 4-year cohort. The most frequent additional deficiencies were thyroid-stimulating hormone (47 patients) and gonadotropins (23 patients). Compared with those who remained with IGHD, children who developed MPHD had more severe GHD at study entry, significantly lower baseline insulin-like growth factor1, peak stimulated growth hormone, and more frequent diagnosis of intracranial tumour or mutation of gene(s) controlling hypothalamic-pituitary development and/or function. Multivariate logistic regression analyses identified female gender, longer follow-up, higher baseline age and lower peak stimulated growth hormone as predictors of MPHD development.

CONCLUSIONS

MPHD is more likely to develop in patients with severe organic IGHD, especially those with history of intracranial tumour or mutation of gene(s) controlling hypothalamic-pituitary development and/or function. Older baseline age, female gender and longer follow-up duration were also associated with higher incidence of MPHD. Long-term monitoring of pituitary function is recommended, irrespective of the aetiology of GHD.

Early retesting by GHRH + arginine test shows normal GH response in most children with idiopathic GH deficiency

PURPOSE

Most children with idiopathic isolated GH deficiency (IGHD) normalize GH response to stimulation tests when retested at the completion of growth. The objective of this study was to test the effectiveness of early retesting in challenging the diagnosis of idiopathic IGHD and critically review the diagnostic workup leading to this diagnosis in children with short stature.

METHODS

We cross-sectionally retested 38 children with idiopathic IGHD and still on GH treatment. The initial diagnosis of idiopathic IGHD was based on subnormal GH responses to two stimulation tests and normal brain imaging or minor/nonspecific findings at magnetic resonance. The GH response normalization at retesting was considered as the main outcome measure. Clinical features of children who were falsely classified as idiopathic IGHD based on first GH testing were retrospectively analyzed.

RESULTS

GH secretion was normal in 36/38 children (95%). Two children showed slightly reduced peak GH responses and normal IGF-I levels. Fourteen children underwent GH retesting before puberty, 24 children during puberty.

CONCLUSION

The diagnostic process should be improved to minimize the rate of false positive at GH testing and, in case of unsatisfactory response to GH treatment, the diagnosis of isolated idiopathic GHD should be challenged with early retesting.

Development of additional pituitary hormone deficiencies in pediatric patients originally diagnosed with idiopathic isolated GH deficiency

OBJECTIVE

We assessed the characteristics of children initially diagnosed with idiopathic isolated GH deficiency (IGHD) who later developed additional (multiple) pituitary hormone deficiencies (MPHD).

DESIGN

Data were analyzed for 5805 pediatric patients with idiopathic IGHD, who were GH-naïve at baseline and GH-treated in the multinational, observational Genetics and Neuroendocrinology of Short Stature International Study.

METHODS

Development of MPHD was assessed from investigator diagnoses, adverse events, and concomitant medications. Analyses were performed for all patients and for those who developed MPHD within 4.5 years or had ≥3.5 years, follow-up and continued to have IGHD (4-year cohort).

RESULTS

MPHD developed in 118/5805 (2.0%) children overall, and in 96/1757 (5.5%) in the 4-year cohort. Patients who developed MPHD had more profound GHD, with decreased height SDS, IGF1 SDS and peak stimulated GH, and greater height decrement vs target, compared with children who continued to have IGHD (P<0.001 for each variable). Delivery complications, congenital anomalies, and perinatal/neonatal adverse events occurred more frequently in patients who developed MPHD. The most frequent additional deficiency was TSH (82 patients overall); four patients developed two pituitary hormone deficiencies and one developed three deficiencies. Multivariable logistic regression indicated that years of follow-up (odds ratio 1.55), baseline age (1.17), baseline height SDS (0.69), and peak stimulated GH (0.64) were associated with the development of MPHD.

CONCLUSIONS

MPHD is more likely to develop in patients with more severe idiopathic IGHD. Older baseline age, lower baseline height SDS, and longer follow-up duration are associated with increased risk of development of MPHD.

Magnetic resonance imaging of CNS in 15,043 children with GH deficiency in KIGS (Pfizer International Growth Database)

OBJECTIVES

Neuroimaging has become an essential part of the diagnostic process in children with GH deficiency (GHD). The aim of the study was to document the frequency of neuroanatomical abnormalities in a very large cohort of children with GHD and to relate these findings to patient clinical characteristics.

DESIGN AND METHODS

Results of magnetic resonance imaging (MRI) were reported in 15,043 of 43,725 children with non-acquired GHD (idiopathic, neurosecretory dysfunction (NSD) and known congenital cause) who were enrolled in KIGS (Pfizer International Growth Database) between 1987 and 2011. Clinical characteristics of patients before GH treatment with normal MRI (idiopathic GHD (IGHD) and NSD) were compared with those of patients with abnormal pituitaries (hypoplasia, empty sella (ES), HME (hypoplastic anterior pituitary, missing pituitary stalk and ectopic posterior pituitary)).

RESULTS

Abnormal MRIs were found in 4032 (26.8%) children, within which ES (N=1178 (7.8%)) and HME (N=1019 (6.8%)) were the most frequent findings. In 2361 children diagnosed as IGHD or NSD before MRI examination, anatomical abnormalities ((pituitary hypoplasia: n=974); (HME: n=459)) were documented. Patients with anatomical abnormalities had more severe characteristics of GHD: normal MRI < pituitary hypoplasia < ES < HME.

CONCLUSIONS

GHD is associated with a great variety of neuroanatomical abnormalities as identified by MRI. The investigation and evaluation of MRI need to be conducted in a structured mode. There is an association between anatomical and functional abnormalities of the pituitary.

The use of neuroimaging for assessing disorders of pituitary development

Magnetic resonance imaging (MRI) is the radiological examination method of choice for evaluating hypothalamo-pituitary-related endocrine disease and is considered essential in the assessment of patients with suspected hypothalamo-pituitary pathology. Physicians involved in the care of such patients have, in MRI, a valuable tool that can aid them in determining the pathogenesis of their patients' underlying pituitary conditions. Indeed, the use of MRI has led to an enormous increase in our knowledge of pituitary morphology, improving, in particular, the differential diagnosis of hypopituitarism. Specifically, MRI allows detailed and precise anatomical study of the pituitary gland by differentiating between the anterior and posterior pituitary lobes. MRI recognition of pituitary hyperintensity in the posterior part of the sella, now considered a marker of neurohypophyseal functional integrity, has been the most striking finding in the diagnosis and understanding of certain forms of 'idiopathic' and permanent growth hormone deficiency (GHD). Published data show a number of correlations between pituitary abnormalities as observed on MRI and a patient's endocrine profile. Indeed, several trends have emerged and have been confirmed: (i) a normal MRI or anterior pituitary hypoplasia generally indicates isolated growth hormone deficiency that is mostly transient and resolves upon adult height achievement; (ii) patients with multiple pituitary hormone deficiencies (MPHD) seldom show a normal pituitary gland; and (iii) the classic triad of ectopic posterior pituitary, pituitary stalk hypoplasia/agenesis and anterior pituitary hypoplasia is more frequently reported in MPHD patients and is generally associated with permanent GHD. Pituitary abnormalities have also been reported in patients with hypopituitarism carrying mutations in several genes encoding transcription factors. Establishing endocrine and MRI phenotypes is extremely useful for the selection and management of patients with hypopituitarism, both in terms of possible genetic counselling and in the early diagnosis of evolving anterior pituitary hormone deficiencies. Going forward, neuroimaging techniques are expected to progressively expand and improve our knowledge and understanding of pituitary diseases.

Posterior pituitary (PP) evaluation in patients with anterior pituitary defect associated with ectopic PP and septo-optic dysplasia

OBJECTIVE

Controversies exist about posterior pituitary (PP) function in subjects with ectopic PP (EPP) and with cerebral midline defects and/or their co-occurrence. We investigate water and electrolyte disturbances in patients at risk for PP dysfunction.

DESIGN

The study was conducted in a single Pediatric Endocrinology Research Unit.

METHODS

Forty-two subjects with childhood-onset GH deficiency were subdivided into five groups: normal magnetic resonance imaging (n=8, group 1); EPP (n=15, group 2); septo-optic dysplasia (SOD) with normal PP (n=4, group 3); EPP and SOD without (n=7, group 4), and with additional midline brain abnormalities (n=8, group 5). At a mean age of 16.0±1.1 years, they underwent a 120 min i.v. infusion with hypertonic 5% saline and evaluation of plasma osmolality (Posm), arginine vasopressin (AVP), thirst score (in groups 1 and 2), and urinary osmolality were performed.

RESULTS

Mean Posm and AVP significantly increased from baseline scores (284.7±4.9 mosm/kg and 0.6±0.2 pmol/l) to 120 min after saline infusion (300.5±8.0 mosm/kg and 10.3±3.3 pmol/l, P<0.0001). Group 5 showed higher mean Posm and lower mean AVP at all time points (P<0.0001). Mean thirst score did not show a significantly different trend between the groups 1 and 2. Urine osmolality was above 750 mosm/kg in all but seven patients after osmotic challenge.

CONCLUSIONS

Patients with midline brain abnormalities and EPP have defective osmoregulated AVP. Patients with EPP and congenital hypopituitarism have normal PP function.

The role of homeodomain transcription factors in heritable pituitary disease

The anterior pituitary gland secretes hormones that regulate developmental and physiological processes, including growth, the stress response, metabolic status, reproduction and lactation. During embryogenesis, cellular determination and differentiation events establish specialized hormone-secreting cell types within the anterior pituitary gland. These developmental decisions are mediated in part by the actions of a cascade of transcription factors, many of which belong to the homeodomain class of DNA-binding proteins. The discovery of some of these regulatory proteins has facilitated genetic analyses of patients with hormone deficiencies. The findings of these studies reveal that congenital defects-ranging from isolated hormone deficiencies to combined pituitary hormone deficiency syndromes-are sometimes associated with mutations in the genes encoding pituitary-acting developmental transcription factors. The phenotypes of affected individuals and animal models have together provided useful insights into the biology of these transcription factors and have suggested new hypotheses for testing in the basic science laboratory. Here, we summarize the gene regulatory pathways that control anterior pituitary development, with emphasis on the role of the homeodomain transcription factors in normal pituitary organogenesis and heritable pituitary disease.

[Perinatal adverse events and neuroanatomical abnormalities in patients with idiopathic hypopituitarism]

OBJECTIVE

To analyze the possible causes of growth hormone (GH) deficiency, whether isolated (GHD) or in combination with other pituitary deficiencies classified as idiopathic.

PATIENTS AND METHODS

We studied patients with idiopathic GHD included in a protocol of recombinant GH treatment in adults attending the outpatient clinic of the Endocrinology and Nutrition Service of the San Cecilio University Hospital. Perinatal history, findings on magnetic resonance imaging (MRI) of the hypothalamic-pituitary axis and diagnosis of GHD and other deficiencies were retrospectively evaluated.

RESULTS

A total of 17 patients were included: 14 men and 3 women with a mean age at diagnosis of 8.4+/-7.3 years. Perinatal adverse events occurred in 12 patients (69.2%). MRI showed empty sella (2 patients), pituitary hypoplasia or absence of the pituitary stalk (7 patients) and pituitary hypoplasia with ectopic posterior pituitary gland (6 patients); in the remaining 2 patients these data were not available. All had an established diagnosis of GHD: 15 with (88.2%) gonadotropin deficiency, 9 (52.9%) with adrenocorticotropic hormone (ACTH) deficiency and 8 (47.1%) with thyroid-stimulating hormone (TSH) deficiency.

CONCLUSIONS

In our patients, adverse events during pregnancy or the perinatal period and the presence of anatomical abnormalities identified by MRI are a marker of pituitary dysfunction and may be important in the pathogenesis of this entity. The clinical spectrum of disease varies from isolated GH deficiency to multiple pituitary hormone deficiencies.

Severe hyponatremia due to ACTH insufficiency in a 14 year-old girl with growth hormone deficiency

SIADH-like hyponatremia as the presenting manifestation of ACTH deficiency is rare in childhood. Here we report a 14 year-old girl who, after 8 years of GH replacement and subsequent treatment for subclinical secondary hypothyroidism, presented with confusion and disorientation due to severe hyponatremia. When her pituitary axis was re-assessed, she was diagnosed as having ACTH deficiency associated with multiple pituitary hormone deficiencies (MPHD) (including GH, FSH, LH, and subclinical TSH deficiencies). She responded poorly to treatment with only hypertonic fluid, but improved after addition of hydrocortisone replacement. The purpose of this paper is to emphasize the importance of suspecting ACTH insufficiency in children with GH deficiency if hyponatremia develops.

The glucagon test in the diagnosis of growth hormone deficiency in children with short stature younger than 6 years

CONTEXT

Few studies have addressed the diagnostic role of the glucagon test in children with suspected GH deficiency (GHD).

OBJECTIVE

The objective of the study was to investigate the diagnostic value of the glucagon test as an alternative test to insulin tolerance test (ITT) and arginine in GHD children younger than 6 yr.

DESIGN AND SETTING

This study was conducted in two pediatric endocrinology centers.

PATIENTS AND METHODS

Forty-eight children (median age 4.2 yr, median height -3.0 sd score) with GHD confirmed by a peak GH to ITT and arginine less than 10 microg/liter (median 4.7 and 3.4 microg/liter, respectively) underwent a glucagon stimulation test. Magnetic resonance imaging showed normal hypothalamic-pituitary anatomy in 24 children, isolated anterior pituitary hypoplasia in seven, and structural hypothalamic-pituitary abnormalities in 17.

RESULTS

Median GH peak response to glucagon (13.5 microg/liter) was significantly higher than that observed after ITT and arginine (P < 0.0001). GH peak after glucagon was less than 10 microg/liter in 20 subjects (group 1) and greater than 10 microg/liter in 28 subjects (group 2) without significant clinical or biochemical differences between the two groups. Median GH peak after glucagon was similar between patients with multiple pituitary hormone deficiency and those with isolated GHD and between subjects with and without structural hypothalamic-pituitary abnormalities. The magnitude of the GH peak after glucagon was negatively correlated to age at diagnosis (rho = -0.636, P < 0.0001).

CONCLUSIONS

This study shows that glucagon has an effective GH-releasing activity and can be used to evaluate somatotroph function in young children with short stature. Normative data for this test in young children need to be established before its use in clinical practice.

Congenital hypopituitarism: clinical, molecular and neuroradiological correlates

OBJECTIVE

Recent studies have suggested that mutations in genes encoding several hypothalamo-pituitary (H-P) transcription factors result in hypopituitarism [isolated GH deficiency (IGHD) and combined pituitary hormone deficiency (CPHD)], which may in turn be related to the neuroanatomy revealed by magnetic resonance (MR) imaging. Although studies have focused on patients with either optic nerve hypoplasia (ONH) or isolated hypopituitarism with normal optic nerves, few studies have compared the two groups. We aimed to relate the clinical phenotype of a large cohort (n = 170) of children with congenital hypopituitarism including septo-optic dysplasia (SOD) attending a single centre to the neuroradiological and genetic findings.

DESIGN

Clinical, biochemical, MR imaging and molecular data were analysed retrospectively in 170 patients with or 'at-risk' (with ONH) of hypopituitarism to determine predictors of hypopituitarism.

RESULTS

The presence of ONH was significantly associated with an absent septum pellucidum [odds ratio (OR) 31.5, 95% confidence intervals (CI) 7.3-136.6, P < 0.001], an abnormal corpus callosum (OR 10.5, 95% CI 3.8-28.6, P < 0.001) and stalk abnormalities (OR 2.3, 95% CI 1.2-4.2, P = 0.009). The risk of hypopituitarism was 27.2 times greater in patients with an undescended posterior pituitary (95% CI 3.6-205.1, P < 0.001). Anterior pituitary hypoplasia (OR 3.1, 95% CI 1.3-7.0, P = 0.006) and an absent pituitary stalk (P < 0.001) were also significantly associated with hypopituitarism. With respect to the type or severity of hypopituitarism, CPHD was more often associated with an abnormal corpus callosum (OR 6.1, 95% CI 1.4-27.4, P = 0.008) and stalk abnormalities (OR 2.8, 95% CI 1.3-6.1, P = 0.006). Male to female ratio was significantly greater in patients with normal optic nerves (3.3:1) as compared with those with ONH (1.2:1). The prevalence of diabetes insipidus, thyrotrophin and ACTH deficiencies was significantly greater in patients with ONH as compared with 'idiopathic' hypopituitarism. Mutations in pituitary transcription factors and genes regulating GH secretion were rare (5/170) in this cohort of patients with sporadic hypopituitarism.

CONCLUSION

Our data suggest that individuals presenting with ONH are at high risk for neuroradiologic and endocrine abnormalities. The neuroradiologic features are predictive not only of the presence, but also of the type, of hypopituitarism. The association of midline abnormalities with hypopituitarism in this cohort suggests a common developmental origin for these features, the aetiology of which remains unidentified in the majority of cases.

Idiopathic short stature: definition, epidemiology, and diagnostic evaluation

Idiopathic short stature is a condition in which the height of the individual is more than 2 SD below the corresponding mean height for a given age, sex and population, in whom no identifiable disorder is present. It can be subcategorized into familial and non-familial ISS, and according to pubertal delay. It should be differentiated from dysmorphic syndromes, skeletal dysplasias, short stature secondary to a small birth size (small for gestational age, SGA), and systemic and endocrine diseases. ISS is the diagnostic group that remains after excluding known conditions in short children.

Contribution of magnetic resonance imaging in non-tumoral hypopituitarism in children

BACKGROUND

Magnetic resonance imaging (MRI) is of paramount importance for evaluating the hypothalamo-pituitary axis in children.

METHODS

We summarize the main points of the MRI technique, and describe the normal appearance of the hypothalamo-pituitary axis as a function of age and pubertal status. The most frequent causes of non-tumoral hypopituitarism include anterior pituitary deficiency (growth hormone deficiency may be isolated or associated with other anterior pituitary hormone deficiencies, with or without other malformations, and related to a known genetic abnormality in some cases), isolated hypogonadotropic hypogonadism and posterior pituitary deficiency with or without anterior pituitary hormone deficiency (central diabetes insipidus may be observed without tumor development).

RESULTS

We describe in detail the appearance of the adenohypophysis, the pituitary stalk and the neurohypophysis, correlations with hormone deficiencies, the abnormalities that may be associated and progression over time for each condition.

CONCLUSION

An accurate description of hypothalamo-pituitary axis abnormalities is necessary for accurate diagnosis and prognosis evaluation, with certain features suggestive of particular diseases and some prognostic data correlated with phenotype.

Assessment of serum IGF-I concentrations in the diagnosis of isolated childhood-onset GH deficiency: a proposal of the Italian Society for Pediatric Endocrinology and Diabetes (SIEDP/ISPED)

The diagnosis of GH deficiency (GHD) is based on the measurement of peak GH responses to pharmacological stimuli. Pharmacological stimuli, however, lack precision, accuracy, are not reproducible, are invasive, non-physiological and some may even be hazardous. Furthermore, different GH commercial assays used to measure GH in serum yield results that may differ considerably. In contrast to GH, IGF-I can be measured on a single, randomly-obtained blood sample. A review of the available data indicates that IGF-I measurement in the diagnosis of childhood-onset isolated GHD has a specificity of up to 100%, with a sensitivity ranging from about 70 to 90%. We suggest an algorithm in which circulating levels of IGF-I together with the evaluation of auxological data, such as growth rate and growth, may be used to assess the likelihood of GHD in pre-pubertal children.

Hypothalamic-pituitary magnetic resonance imaging in growth hormone deficiency

The accurate analysis of the hypothalamic-pituitary area is essential in the diagnosis of endocrine-related diseases. High-quality magnetic resonance imaging represents the examination modality of choice in the evaluation of hypothalamic-pituitary morphology. Indeed, the advent of molecular biology and neuroimaging techniques has led to significant progress in the understanding of the pathogenesis of disorders affecting the pituitary gland, specifically by demonstrating a clear phenotype-genotype relationship. Animal studies, along with the correlation of a particular genetic profile to certain endocrine and magnetic resonance imaging phenotypes in humans, have yielded great insights into pituitary development. Today, there is convincing evidence to support the hypothesis that marked magnetic resonance imaging differences in pituitary morphology indicate a variety of disorders that affect anterior pituitary gland organogenesis and function with a variety of diverse prognoses.

MRI of the hypothalamic-pituitary axis in children

In childhood, the MR characteristics of the normal pituitary gland are well established. During the first 2 months of life the adenohypophysis demonstrates high signal. Pituitary gland height (PGH) decreases during the 1st year of life and then increases, reaching a plateau after puberty. The magnetization transfer ratio (MTR) increases in both sexes up to the age of 20 years. On dynamic contrast-enhanced studies, the posterior pituitary lobe enhances simultaneously with the straight sinus, and the adenohypophysis later, but within 30 s. In genetically determined dysfunctional states, the adenohypophysis may be normal, hypoplastic, or enlarged. Pituitary enlargement, observed in Prop 1 gene mutations, is characterized by a mass interposed between the anterior and posterior lobes. An ectopic posterior lobe (EPP), associated with a hypoplastic or absent pituitary stalk, may be observed in patients with hypopituitarism. Tumors of the hypothalamic-pituitary (HP) axis may be the origin of adenohypophyseal deficiencies. A small hypo-intense adenohypophysis is found in iron overload states and is often associated with hypogonadotrophic hypogonadism. Absence of the posterior lobe bright signal, with or without a thick pituitary stalk or a mass at any site from the median eminence to the posterior pituitary lobe, may be found in diabetes insipidus. Hydrocephalus, suprasellar arachnoid cysts, hypothalamic hamartomas and craniopharyngiomas may result in central precocious puberty (CPP). Increased PGH in girls with idiopathic CPP is useful for its differential diagnosis from premature thelarche (PT). Pituitary adenomas, observed mainly in adolescents, present the same MR characteristics as those in adults.