Translating the potential of the urine steroid metabolome to stage NAFLD (TrUSt-NAFLD): study protocol for a multicentre, prospective validation study

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) affects approximately one in four individuals and its prevalence continues to rise. The advanced stages of NAFLD with significant liver fibrosis are associated with adverse morbidity and mortality outcomes. Currently, liver biopsy remains the 'gold-standard' approach to stage NAFLD severity. Although generally well tolerated, liver biopsies are associated with significant complications, are resource intensive, costly, and sample only a very small area of the liver as well as requiring day case admission to a secondary care setting. As a result, there is a significant unmet need to develop non-invasive biomarkers that can accurately stage NAFLD and limit the need for liver biopsy. The aim of this study is to validate the use of the urine steroid metabolome as a strategy to stage NAFLD severity and to compare its performance against other non-invasive NAFLD biomarkers.

METHODS AND ANALYSIS

The TrUSt-NAFLD study is a multicentre prospective test validation study aiming to recruit 310 patients with biopsy-proven and staged NAFLD across eight centres within the UK. 150 appropriately matched control patients without liver disease will be recruited through the Oxford Biobank. Blood and urine samples, alongside clinical data, will be collected from all participants. Urine samples will be analysed by liquid chromatography-tandem mass spectroscopy to quantify a panel of predefined steroid metabolites. A machine learning-based classifier, for example, Generalized Matrix Relevance Learning Vector Quantization that was trained on retrospective samples, will be applied to the prospective steroid metabolite data to determine its ability to identify those patients with advanced, as opposed to mild-moderate, liver fibrosis as a consequence of NAFLD.

ETHICS AND DISSEMINATION

Research ethical approval was granted by West Midlands, Black Country Research Ethics Committee (REC reference: 21/WM/0177). A substantial amendment (TrUSt-NAFLD-SA1) was approved on 26 November 2021.

TRIAL REGISTRATION NUMBER

ISRCTN19370855.

Tumour microenvironment and pituitary tumour behaviour

The pituitary tumour microenvironment encompasses a spectrum of non-tumoural cells, such as immune, stromal or endothelial cells, as well as enzymes and signalling peptides like cytokines, chemokines and growth factors, which surround the tumour cells and may influence pituitary tumour behaviour and tumourigenic mechanisms. Recently, there has been intensive research activity in this field describing various pituitary tumour-infiltrating immune and stromal cell subpopulations, and immune- and microenvironment-related pathways. Key changes in oncological therapeutic avenues resulted in the recognition of pituitary as a target of adverse events for patients treated with immune checkpoint regulators. However, these phenomena can be turned into therapeutic advantage in severe cases of pituitary tumours. Therefore, unravelling the pituitary tumour microenvironment will allow a better understanding of the biology and behaviour of pituitary tumours and may provide further developments in terms of diagnosis and management of patients with aggressively growing or recurrent pituitary tumours.

Novel AIP mutation in exon 6 causing acromegaly in a German family

The most frequent genetic alteration of familial isolated growth hormone producing pituitary neuroendocrine tumors is a germline mutation of the aryl hydrocarbon receptor-interacting protein (AIP) gene. Various AIP mutations are already known; however, an AIP mutation in exon 6 (c.811_812del; p.Arg271Glyfs*16) has not been reported yet. Here, we report a German family with two identical twins who were both affected by acromegaly and carried the above-mentioned novel AIP mutation. The father was found to be an unaffected carrier, while the paternal aunt most likely suffered from acromegaly as well and died from metastatic colorectal cancer. Apart from reporting a novel AIP mutation, this study does not only highlight the different clinical and histological features of the AIP mutated growth hormone producing pituitary neuroendocrine tumors but also confirms the poor responsiveness of dopamine agonists in AIP mutated acromegaly. Furthermore, it highlights the increased mortality risk of comorbidities typically associated with acromegaly.

Pituitary MRI Features in Acromegaly Resulting From Ectopic GHRH Secretion From a Neuroendocrine Tumor: Analysis of 30 Cases

CONTEXT

Ectopic acromegaly is a consequence of rare neuroendocrine tumors (NETs) that secrete GHRH. This abnormal GHRH secretion drives GH and IGF-1 excess, with a clinical presentation similar to classical pituitary acromegaly. Identifying the underlying cause for the GH hypersecretion in the setting of ectopic GHRH excess is, however, essential for proper management both of acromegaly and the NET. Owing to the rarity of NETs, the imaging characteristics of the pituitary in ectopic acromegaly have not been analyzed in depth in a large series.

OBJECTIVE

Characterize pituitary magnetic resonance imaging (MRI) features at baseline and after NET treatment in patients with ectopic acromegaly.

DESIGN

Multicenter, international, retrospective.

SETTING

Tertiary referral pituitary centers.

PATIENTS

Thirty ectopic acromegaly patients having GHRH hypersecretion.

INTERVENTION

None.

MAIN OUTCOME MEASURE

MRI characteristics of pituitary gland, particularly T2-weighted signal.

RESULTS

In 30 patients with ectopic GHRH-induced acromegaly, we found that most patients had hyperplastic pituitaries. Hyperplasia was usually moderate but was occasionally subtle, with only small volume increases compared with normal ranges for age and sex. T2-weighted signal was hypointense in most patients, especially in those with hyperplastic pituitaries. After treatment of the NET, pituitary size diminished and T2-weighted signal tended to normalize.

CONCLUSIONS

This comprehensive study of pituitary MRI characteristics in ectopic acromegaly underlines the utility of performing T2-weighted sequences in the MRI evaluation of patients with acromegaly as an additional tool that can help to establish the correct diagnosis.

Treatment of congenital adrenal hyperplasia in children aged 0-3 years: a retrospective multicenter analysis of salt supplementation, glucocorticoid and mineralocorticoid medication, growth and blood pressure

OBJECTIVES

International guidelines recommend additional salt supplementation during infancy in classic congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. The influence of corticoid medication and growth has not been assessed.

AIM

To investigate the current use of salt supplementation, fludrocortisone (FC) and hydrocortisone (HC) dosage as well as weight, height, BMI and blood pressure (BP) in CAH children aged 0-3 years.

METHODS

Retrospective multicentre analysis using data from the I-CAH registry. Salt-treated (ST) and non-salt-treated (NST) children were compared regarding FC and HC dosage, weight, height and BP at 0, 3, 6, 9, 12, 18, 24, 30, and 36 months.

RESULTS

We analysed 2483 visits of 331 patients born after year 2000 in 13 countries (male, n = 145) with 203 ST patients (61%). NST children had significantly higher FC dosages at 1.5-4.5 months and higher HC dosages until 1.5 months of age. No differences in weight, length and BP between subgroups were observed. Children of the whole cohort showed increased BMI-SDS during the study period and about half of the reported BP readings were >P95.

CONCLUSION

In children treated with additional salt supplementation, FC and HC dosages are lower during the first months of life but without differences in weight, length and BP until 3 years of age compared to NST children. All children showed an increase in BMI-SDS and a high rate of BP readings >P95 until 3 years, indicating the start of weight gain and negative effects on blood pressure already in very early life.

Epigenetic and post-transcriptional regulation of somatostatin receptor subtype 5 (SST5 ) in pituitary and pancreatic neuroendocrine tumors

Somatostatin receptor subtype 5 (SST₅) is an emerging biomarker and actionable target in pituitary (PitNETs) and pancreatic (PanNETs) neuroendocrine tumors. Transcriptional and epigenetic regulation of SSTR5 gene expression and mRNA biogenesis is poorly understood. Recently, an overlapping natural antisense transcript, SSTR5‐AS1, potentially regulating SSTR5 expression, was identified. We aimed to elucidate whether epigenetic processes contribute to the regulation of SSTR5 expression in PitNETs (somatotropinomas) and PanNETs. We analyzed the SSTR5/SSTR5‐AS1 human locus in silico to identify CpG islands. SSTR5 and SSTR5‐AS1 expression was assessed by quantitative real‐time PCR (qPCR) in 27 somatotropinomas, 11 normal pituitaries (NPs), and 15 PanNETs/paired adjacent (control) samples. We evaluated methylation grade in four CpG islands in the SSTR5/SSTR5‐AS1 genes. Results revealed that SSTR5 and SSTR5‐AS1 were directly correlated in NP, somatotropinoma, and PanNET samples. Interestingly, selected CpG islands were differentially methylated in somatotropinomas compared with NPs. In PanNETs cell lines, SSTR5‐AS1 silencing downregulated SSTR5 expression, altered aggressiveness features, and influenced pasireotide response. These results provide evidence that SSTR5 expression in PitNETs and PanNETs can be epigenetically regulated by the SSTR5‐AS1 antisense transcript and, indirectly, by DNA methylation, which may thereby impact tumor behavior and treatment response.

Cabergoline reduces 3-methoxytyramine in a SDHC patient with metastatic paraganglioma and prolactinoma

SUMMARY

We observed a novel therapeutic response with cabergoline in a male patient with a dopamine-secreting head and neck paraganglioma (HNPGL), macroprolactinoma and germline succinate dehydrogenase C mutation (SDHC). The macroprolactinoma was treated with cabergoline which gave an excellent response. He was found to have raised plasma 3-methoxytyramine of 1014 pmol/L (NR: 0-180 pmol/L); but it was unclear if this was a drug-induced phenomenon from dopamine agonist (DA) therapy. Cabergoline was stopped for 4 weeks and the 3-methoxytyramine level increased significantly to 2185 pmol/L, suggesting a biochemical response of his HNPGL. Subsequently, Gallium-68 Dotatate PET and MRI (Gallium-68 Dotatate PET/MRI) demonstrated a second lesion in the sacrum. Both the HNPGL and metastatic sacral deposit received external beam radiotherapy with a good biochemical and radiological response.

CONCLUSION

Our case report highlights the rare potential of germline SDHC mutations causing metastatic paraganglioma and concurrent pituitary tumours. Cabergoline treatment may lower elevated 3-methoxytyramine levels and, therefore, mask the biochemical evidence of metastatic disease but also may have therapeutic relevance in dopamine-secreting pheochromocytomas/paragangliomas (PPGLs).

LEARNING POINTS

Several neuroendocrine tumours (NETs) express dopamine D2 and D4 receptors. In this case report, cabergoline significantly reduced plasma 3-methoxytyramine level in a patient with functional HNPGL. Cabergoline might have therapeutic relevance in dopamine-secreting PPGLs. Paragangliomas associated with SDHC mutation classically present with asymptomatic non-functional HNPGL and have rare metastatic potential. The association of pheochromocytoma or paraganglioma and pituitary adenoma is now a well-described rare association (<1%), designated as the three P association. While the three P association is most commonly seen with succinate dehydrogenase B and D mutations, it has also been described in patients with SDHA and SDHC mutations. Cabergoline treatment may lower elevated 3-methoxytyramine levels and mask the biochemical evidence of metastatic disease. Regular functional imaging with Gallium-68 Dotatate PET/MRI provides better evidence of metastatic disease.

One Fourth of Adult Patients With Acromegaly Have Tall Stature With Similar Frequency in Males And Females

Introduction: Tall stature (TS) is a manifestation of growth hormone (GH) excess, with higher prevalence reported for males. The aim of this study was (i) to evaluate the relationship between height of patients with GH excess related to midparental height (MPH) and population mean height; (ii) to test whether TS patients with acromegaly come from tall families. Methods: Single-centre, observational study on 101 consecutive adult patients with acromegaly and no family history of pituitary adenoma. Patients were analysed in two subgroups depending on height using country-specific data: 1) normal stature and 2) TS group, defined as either height above gender-specific 97 percentile or as >1.5 country-specific standard deviation (SD) from MPH. Results: Twenty-four percent of acromegaly patients (13 females/11 males) met one or both of the TS criteria. TS patients were significantly younger at the diagnosis (mean±SD, 33.6±13.4 vs 50.6±12.3 years) and at first symptoms (median 27.5, range 23-42 vs 41 (33-54) years) with greater tumour size and higher basal GH concentration than normal stature patients (p<0.01). The TS criteria based on the 1.5 SD above MPH identified more TS patients than the above 97 percentile height (92% vs 38%) and especially increased the diagnosis of TS in women (92% vs 31%). There was no difference in height of family members of acromegaly patients with or without TS. Height of family members were not taller than the population mean. Conclusion: One fourth of adult patients with acromegaly have TS with similar frequency in males and females. Based on our data TS patients with acromegaly do not come from tall families.

P34 Characteristics, diagnosis and management of Cushing’s disease - A systematic review and meta-analysis

Introduction

The clinical practice and research in the diagnosis and management of Cushing’s disease remains heterogeneous and challenging to this day. We sought to establish the characteristics of Cushing’s disease, and the trends in diagnosis, management and reporting in this field.

Methods

Searches of PubMed and Embase were conducted. Study protocol was registered a-priori. Random-effects analyses were conducted to establish numerical estimates.

Results

Our screening returned 159 papers.

The average age of adult patients with Cushing’s disease was 39.3, and 13.6 for children. The male:female ratio was 1:3. 8% of patients had undergone previous transsphenoidal resection. The ratio of macroadenomas: microadenomas:imaging-undetectable adenomas was 18:53:29. The most commonly reported preoperative biochemical investigations were serum cortisol (average 26.4µg/dL) and ACTH (77.5pg/dL). Postoperative cortisol was most frequently used to define remission (74.8%), most commonly with threshold of 5µg/dL (44.8%). Average remission rates were 77.8% with recurrence rate of 13.9%. Median follow-up was 38 months.

Majority of papers reported age (81.9%) and sex (79.4%). Only 56.6% reported whether their patients had previous pituitary surgery. 45.3% reported whether their adenomas were macroadenoma, microadenoma or undetectable. Only 24.1% reported preoperative cortisol, and this did not improve over time. 60.4% reported numerical thresholds for cortisol in defining remission, and this improved significantly over time (p = 0.004). Visual inspection of bubbleplots showed increasing preference for threshold of 5µg/dL. 70.4% reported the length of follow up.

Conclusion

We quantified the characteristics of Cushing’s disease, and analysed the trends in investigation and reporting. This review may help to inform future efforts in forming guidelines for research and clinical practice.

International practice of corticosteroid replacement therapy in congenital adrenal hyperplasia: data from the I-CAH registry

OBJECTIVE

Despite published guidelines no unified approach to hormone replacement in congenital adrenal hyperplasia (CAH) exists. We aimed to explore geographical and temporal variations in the treatment with glucocorticoids and mineralocorticoids in CAH.

DESIGN

This retrospective multi-center study, including 31 centers (16 countries), analyzed data from the International-CAH Registry.

METHODS

Data were collected from 461 patients aged 0-18 years with classic 21-hydroxylase deficiency (54.9% females) under follow-up between 1982 and 2018. Type, dose and timing of glucocorticoid and mineralocorticoid replacement were analyzed from 4174 patient visits.

RESULTS

The most frequently used glucocorticoid was hydrocortisone (87.6%). Overall, there were significant differences between age groups with regards to daily hydrocortisone-equivalent dose for body surface, with the lowest dose (median with interquartile range) of 12.0 (10.0-14.5) mg/m2/day at age 1-8 years and the highest dose of 14.0 (11.6-17.4) mg/m2/day at age 12-18 years. Glucocorticoid doses decreased after 2010 in patients 0-8 years (P < 0.001) and remained unchanged in patients aged 8-18 years. Fludrocortisone was used in 92% of patients, with relative doses decreasing with age. A wide variation was observed among countries with regards to all aspects of steroid hormone replacement.

CONCLUSIONS

Data from the I-CAH Registry suggests international variations in hormone replacement therapy, with a tendency to treatment with high doses in children.

Pituitary Neoplasm Nomenclature Workshop: Does Adenoma Stand the Test of Time?

The WHO Classification of Endocrine Tumours designates pituitary neoplasms as adenomas. A proposed nomenclature change to pituitary neuroendocrine tumors (PitNETs) has been met with concern by some stakeholder groups. The Pituitary Society coordinated the Pituitary Neoplasm Nomenclature (PANOMEN) workshop to address the topic. Experts in pituitary developmental biology, pathology, neurosurgery, endocrinology, and oncology, including representatives nominated by the Endocrine Society, European Society of Endocrinology, European Neuroendocrine Association, Growth Hormone Research Society, and International Society of Pituitary Surgeons. Clinical epidemiology, disease phenotype, management, and prognosis of pituitary adenomas differ from that of most NETs. The vast majority of pituitary adenomas are benign and do not adversely impact life expectancy. A nomenclature change to PitNET does not address the main challenge of prognostic prediction, assigns an uncertain malignancy designation to benign pituitary adenomas, and may adversely affect patients. Due to pandemic restrictions, the workshop was conducted virtually, with audiovisual lectures and written précis on each topic provided to all participants. Feedback was collated and summarized by Content Chairs and discussed during a virtual writing meeting moderated by Session Chairs, which yielded an evidence-based draft document sent to all participants for review and approval. There is not yet a case for adopting the PitNET nomenclature. The PANOMEN Workshop recommends that the term adenoma be retained and that the topic be revisited as new evidence on pituitary neoplasm biology emerges.

ESE audit on management of Adult Growth Hormone Deficiency in clinical practice

Guidelines recommend adults with pituitary disease in whom GH therapy is contemplated, to be tested for GH deficiency (AGHD); however, clinical practice is not uniform.

AIMS

1) To record current practice of AGHD management throughout Europe and benchmark it against guidelines; 2) To evaluate educational status of healthcare professionals about AGHD.

DESIGN

On-line survey in endocrine centres throughout Europe.

PATIENTS AND METHODS

Endocrinologists voluntarily completed an electronic questionnaire regarding AGHD patients diagnosed or treated in 2017-2018.

RESULTS

Twenty-eight centres from 17 European countries participated, including 2139 AGHD patients, 28% of childhood-onset GHD. Aetiology was most frequently non-functioning pituitary adenoma (26%), craniopharyngioma (13%) and genetic/congenital mid-line malformations (13%). Diagnosis of GHD was confirmed by a stimulation test in 52% (GHRH+arginine, 45%; insulin-tolerance, 42%, glucagon, 6%; GHRH alone and clonidine tests, 7%); in the remaining, ≥3 pituitary deficiencies and low serum IGF-I were diagnostic. Initial GH dose was lower in older patients, but only women <26 years were prescribed a higher dose than men; dose titration was based on normal serum IGF-I, tolerance and side-effects. In one country, AGHD treatment was not approved. Full public reimbursement was not available in four countries and only in childhood-onset GHD in another. AGHD awareness was low among non-endocrine professionals and healthcare administrators. Postgraduate AGHD curriculum training deserves being improved.

CONCLUSION

Despite guideline recommendations, GH replacement in AGHD is still not available or reimbursed in all European countries. Knowledge among professionals and health administrators needs improvement to optimize care of adults with GHD.

Identification of a TMEM127 variant in a patient with paraganglioma and acromegaly

SUMMARY

The coincidence of a pheochromocytoma or paraganglioma and a pituitary adenoma in the same patient is a rare condition. In the last few years SDHx and MAX mutations have been identified and discussed as a potential causal connection in cases of coincidence. We describe a case of a middle-aged female patient which presented with acromegaly, a growth hormone-secreting pituitary adenoma and a symptomatic neck paraganglioma. The patient was cured by surgery from both the pituitary tumour and the paraganglioma and is well after ten years follow-up. Due to the unusual coexistence of two neuroendocrine tumours, further molecular genetic testing was performed which revealed a variant in the TMEM127 gene (c245-10C>G).

LEARNING POINTS

Pheochromocytoma/paraganglioma and coexisting functioning pituitary adenoma are a very rare condition. An appropriate treatment of each tumour entity with a multi-disciplinary approach and regular follow-up is needed. The possibility of a hereditary disease should be considered and genetic workup is recommended. Genetic testing should focus primarily on the genes with mutations related to pheochromocytomas and paragangliomas. Next-generation sequencing with multi-gene panel testing is the currently suggested strategy. Genes associated with paragangliomas and pituitary adenomas are SDHA, SDHB, SDHC, SDHD, SDHAF2, MAX and MEN1, while case reports with VHL, RET and NF1 may represent coincidences. Variants of uncertain significance may need ongoing vigilance, in case novel data become available of these variants.

XAF1 as a modifier of p53 function and cancer susceptibility

Cancer risk is highly variable in carriers of the common TP53-R337H founder allele, possibly due to the influence of modifier genes. Whole-genome sequencing identified a variant in the tumor suppressor XAF1 (E134*/Glu134Ter/rs146752602) in a subset of R337H carriers. Haplotype-defining variants were verified in 203 patients with cancer, 582 relatives, and 42,438 newborns. The compound mutant haplotype was enriched in patients with cancer, conferring risk for sarcoma (P = 0.003) and subsequent malignancies (P = 0.006). Functional analyses demonstrated that wild-type XAF1 enhances transactivation of wild-type and hypomorphic TP53 variants, whereas XAF1-E134* is markedly attenuated in this activity. We propose that cosegregation of XAF1-E134* and TP53-R337H mutations leads to a more aggressive cancer phenotype than TP53-R337H alone, with implications for genetic counseling and clinical management of hypomorphic TP53 mutant carriers.

SAT-LB056 Is AIP a Tumor Suppressor or an Oncogene? AIP as a Novel Regulator of the Oncogene BCL6 in Diffuse Large B Cell Lymphoma

Background: Heterozygous germline loss-of-function mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene are usually associated with acromegaly or gigantism due to a young-onset somatotropinoma. AIP functions as a tumor suppressor gene in the pituitary, while its role in other tumours is unknown. AIP is highly expressed in patients with Diffuse Large B Cell Lymphoma (DLBCL) compared to any other tumor type. DLBCL arises from germinal centre B cells which characteristically express the transcriptional repressor B cell lymphoma-6 (BCL6), key for germinal centre formation. Increased expression of BCL6 can lead to the development of DLBCL. Despite the obvious importance of BCL6 expression in GC B cells, the mechanisms by which it is regulated are still poorly understood. Aim: The aim of this study was to investigate the relationship of the high AIP expression, BCL6 and the pathobiology of DLBCL. Methods: We generated mice carrying a conditional homozygous deletion of Aip in T and B cells (Aip^fl/fl;Rag1^Cre/+). Co-localization of AIP and members of the BCL6 ubiquitination/proteasome pathway by immunofluorescence analysis. Ubiquitin-mediated proteasomal degradation study was done by immuno-precipitation (IP). Results: Our study found that AIP is highly expressed in DLBCL. Genetic deletion of Aip revealed that AIP supported BCL6 expression in mice. The ubiquitin E3 ligase FBXO11 has been previously shown to add ubiquitin to BCL6. We found that AIP could bind to the deubiquitinase UCHL1 and that UCHL1 could remove ubiquitin from BCL6 thereby supporting BCL6 expression by preventing FBXO11 mediated degradation of BCL6 recapitulating what we observed in Aip deficient B cells. Conclusions: The data presented here reveal AIP to be a novel positive regulator of BCL6 protein expression which is commonly up-regulated in DLBCL and prevents FBXO11 degradation of BCL6 by enabling the UCHL1 to remove ubiquitin from BCL6. Therefore, AIP is a potential novel therapeutic target to treat DLBCL. It appears that AIP function as a tumor suppressor in the pituitary and as an oncogene to the pathobiology of DLBCL. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

OR32-4 Diagnostic Performance of Macimorelin vs the Insulin Tolerance Test (ITT) in 140 Patients at Varying Growth Hormone (GH) Cutpoints: A Post Hoc Analysis

Background: Macimorelin (MAC), an orally active ghrelin receptor agonist, is indicated for the diagnosis of adult growth hormone deficiency (AGHD) in the United States. The efficacy of MAC for AGHD diagnosis was previously demonstrated; comparing MAC at cutpoint values of 2.8 and 5.1 ng/mL with ITT at cutpoint values of 3.0 and 5.1 ng/mL.^1,2Objective: This post hoc analysis evaluated the percent agreement and sensitivity and specificity of MAC vs ITT over a range of GH cutpoints. Methods: This analysis included data from a phase 3, open-label, randomized, 2-way crossover study of MAC vs ITT in subjects with high (Group A, n=38), intermediate (Group B, n=37), and low (Group C, n=40) likelihood for AGHD and healthy, matched controls (Group D, n=25).¹ Percent agreement (negative, positive, and overall) and estimated sensitivity and specificity were determined using GH cutpoint values of 2.8, 4, 5.1, and 6.5 ng/mL for both MAC and ITT. Results: 74 subjects were classified as GH deficient, and 66 subjects were classified as GH sufficient. These subjects were classified based on the ITT using a cutpoint of 5.1 ng/mL.¹ The highest negative, positive, and overall agreements between tests were observed when GH cutpoints chosen for MAC and ITT were identical to each other and were either 2.8 or 5.1 ng/mL. With a GH cutpoint value of 2.8 ng/mL for both tests, negative agreement was 94% (95% CI: 86%, 98%), positive agreement was 87% (95% CI: 76%, 94%), and overall agreement was 91% (95% CI: 85%, 95%). At a GH cutpoint value of 5.1 ng/mL for both tests, negative agreement was 92% (95% CI: 83%, 97%), positive agreement was 82% (95% CI: 72%, 90%), and overall agreement was 87% (95% CI: 80%, 92%). Assuming all Group A participants were cases and all Group D participants were controls, estimated specificities of MAC and ITT were identical (96%) at GH cutpoint values of 2.8, 4, or 5.1 ng/mL. Estimated sensitivity for ITT at GH cutpoint value of 5.1 ng/mL (97%) was higher than for MAC at cutpoint value of 2.8 ng/mL (87%); increasing the test cutpoint to 6.5 ng/mL increased sensitivity to 97% and 100% for MAC and ITT, respectively, but at the expense of specificity decreases to 92% (MAC) and 88% (ITT). Conclusions: Among the cutpoints examined, agreement between MAC and ITT was highest at either 2.8 or 5.1 ng/mL, with positive agreement declining modestly at the higher cutpoint. Sensitivity of MAC was maximal at 6.5 ng/mL but at the expense of a decline in specificity from 96% to 92%, which may be undesirable if the primary consideration is minimization of false-positive diagnosis of AGHD. A MAC cutpoint of 5.1 ng/mL provides maximal specificity (96%) and high sensitivity (92%) with good overall agreement to ITT at the same cutpoint (87%), making it clinically useful for the diagnosis of AGHD. Reference: 1. Garcia JM, et al. J Clin Endocrinol Metab. 2018;103(8):3083-3093. 2. Garcia JM, et al. Presented at ENEA; 17-20 October 2018; Wroclaw, Poland.

Natural history, treatment, and long-term follow up of patients with multiple endocrine neoplasia type 2B: an international, multicentre, retrospective study

BACKGROUND

Multiple endocrine neoplasia type 2B is a rare syndrome caused mainly by Met918Thr germline RET mutation, and characterised by medullary thyroid carcinoma, phaeochromocytoma, and extra-endocrine features. Data are scarce on the natural history of multiple endocrine neoplasia type 2B. We aimed to advance understanding of the phenotype and natural history of multiple endocrine neoplasia type 2B, to increase awareness and improve detection.

METHODS

This study was a retrospective, multicentre, international study in patients carrying the Met918Thr RET variant with no age restrictions. The study was done with registry data from 48 centres globally. Data from patients followed-up from 1970 to 2016 were retrieved from May 1, 2016, to May 31, 2018. Our primary objectives were to determine overall survival, and medullary thyroid carcinoma-specific survival based on whether the patient had undergone early thyroidectomy before the age of 1 year. We also assessed remission of medullary thyroid carcinoma, incidence and treatment of phaeochromocytoma, and the penetrance of extra-endocrine features.

FINDINGS

345 patients were included, of whom 338 (98%) had a thyroidectomy. 71 patients (21%) of the total cohort died at a median age of 25 years (range <1-59). Thyroidectomy was done before the age of 1 year in 20 patients, which led to long-term remission (ie, undetectable calcitonin level) in 15 (83%) of 18 individuals (2 patients died of causes unrelated to medullary thyroid carcinoma). Medullary thyroid carcinoma-specific survival curves did not show any significant difference between patients who had thyroidectomy before or after 1 year (comparison of survival curves by log-rank test: p=0·2; hazard ratio 0·35; 95% CI 0.07-1.74). However, there was a significant difference in remission status between patients who underwent thyroidectomy before and after the age of 1 year (p<0·0001). There was a significant difference in remission status between patients who underwent thyroidectomy before and after the age of 1 year (p<0·0001). In the other 318 patients who underwent thyroidectomy after 1 year of age, biochemical and structural remission was obtained in 47 (15%) of 318 individuals. Bilateral phaeochromocytoma was diagnosed in 156 (50%) of 313 patients by 28 years of age. Adrenal-sparing surgery was done in 31 patients: three (10%) of 31 patients had long-term recurrence, while normal adrenal function was obtained in 16 (62%) patients. All patients with available data (n=287) had at least one extra-endocrine feature, including 106 (56%) of 190 patients showing marfanoid body habitus, mucosal neuromas, and gastrointestinal signs.

INTERPRETATION

Thyroidectomy done at no later than 1 year of age is associated with a high probability of cure. The reality is that the majority of children with the syndrome will be diagnosed after this recommended age. Adrenal-sparing surgery is feasible in multiple endocrine neoplasia type 2B and affords a good chance for normal adrenal function. To improve the prognosis of such patients, it is imperative that every health-care provider be aware of the extra-endocrine signs and the natural history of this rare syndrome. The implications of this research include increasing awareness of the extra-endocrine symptoms and also recommendations for thyroidectomy before the age of 1 year.

FUNDING

None.

The current landscape of European registries for rare endocrine conditions

Objective To identify cross-border international registries for rare endocrine conditions that are led from Europe and to understand the extent of engagement with these registries within a network of reference centres (RCs) for rare endocrine conditions. Methods Database search of international registries and a survey of RCs in the European Reference Network for rare endocrine conditions (Endo-ERN) with an overall response rate of 82%. Results Of the 42 conditions with orphacodes currently covered within Endo-ERN, international registries exist for 32 (76%). Of 27 registries identified in the Orphanet and RD-Connect databases, Endo-ERN RCs were aware of 11 (41%). Of 21 registries identified by the RC, RD-Connect and Orphanet did not have a record of 10 (48%). Of the 29 glucose RCs, the awareness and participation rate in an international registry was highest for rare diabetes at 75 and 56% respectively. Of the 37 sex development RCs, the corresponding rates were highest for disorders of sex development at 70 and 52%. Of the 33 adrenal RCs, the rates were highest for adrenocortical tumours at 68 and 43%. Of the 43 pituitary RCs, the rates were highest for pituitary adenomas at 43 and 29%. Of the 31 genetic tumour RCs, the rates were highest for MEN1 at 26 and 9%. For the remaining conditions, awareness and participation in registries was less than 25%. Conclusion Although there is a need to develop new registries for rare endocrine conditions, there is a more immediate need to improve the awareness and participation in existing registries.

De novo HNF1 homeobox B mutation as a cause for chronic, treatment-resistant hypomagnesaemia

29-year-old female presenting with an 8-year history of unexplained hypomagnesaemia, which was severe enough to warrant intermittent inpatient admission for intravenous magnesium. Urinary magnesium was inappropriately normal in the context of hypomagnesaemia indicating magnesium wasting. Ultrasound imaging demonstrated unilateral renal cysts and computed tomography of kidneys, ureters and bladder showed a bicornuate uterus. Referral to genetic services and subsequent testing revealed a de novo HNF1B deletion.

From pituitary adenoma to pituitary neuroendocrine tumor (PitNET): an International Pituitary Pathology Club proposal

The classification of neoplasms of adenohypophysial cells is misleading because of the simplistic distinction between adenoma and carcinoma, based solely on metastatic spread and the poor reproducibility and predictive value of the definition of atypical adenomas based on the detection of mitoses or expression of Ki-67 or p53. In addition, the current classification of neoplasms of the anterior pituitary does not accurately reflect the clinical spectrum of behavior. Invasion and regrowth of proliferative lesions and persistence of hormone hypersecretion cause significant morbidity and mortality. We propose a new terminology, pituitary neuroendocrine tumor (PitNET), which is consistent with that used for other neuroendocrine neoplasms and which recognizes the highly variable impact of these tumors on patients.

Metformin prevents metabolic side effects during systemic glucocorticoid treatment

OBJECTIVES

Patients receiving glucocorticoid treatment are prone to develop metabolic complications. In preclinical studies, metformin prevented the development of the metabolic syndrome during glucocorticoid excess. We herein investigated the metabolic effect of metformin during glucocorticoid treatment in non-diabetic patients.

METHODS

In a double-blind, placebo-controlled trial, patients starting glucocorticoid treatment (prednisone, prednisolone or methylprednisolone) for four weeks were randomised to concomitantly receive metformin (850 mg once daily for one week followed by 850 mg twice daily for three weeks) or placebo. All patients underwent a standardised oral glucose tolerance test at baseline and after four weeks. The primary endpoint was change in the 2-h area under the curve (AUC) of glucose during the oral glucose tolerance test between baseline and four weeks.

RESULTS

29 of 34 randomised non-diabetic patients completed the trial (17 metformin and 12 placebo). In patients allocated to placebo, median glucose 2-h AUC increased from baseline to four weeks (836 (IQR 770-966) to 1202 (1009-1271) mmol/L per min; P = 0.01). In contrast, glucose levels remained similar to baseline in the metformin group (936 (869-1003) to 912 (825-1011) mmol/L per min; P = 0.83). This change within four weeks was different between both groups (P = 0.005). Glucocorticoid equivalent doses were similar in both groups (placebo: 980.0 (560.0-3259.8) mg/28 days; metformin: 683.0 (437.5-1970.5) mg/28 days; P = 0.26).

CONCLUSIONS

In this first randomised controlled trial of metformin targeting metabolic complications in patients needing glucocorticoid therapy, we observed a beneficial effect of metformin on glycaemic control. Metformin thus seems to be a promising drug for preventing metabolic side effects during systemic glucocorticoid treatment.

Sporadic pituitary adenomas: the role of germline mutations and recommendations for genetic screening

Although most pituitary adenomas occur sporadically, these common tumors can present in a familial setting in approximately 5% of cases. Germline mutations in several genes with autosomal dominant (AIP, MEN1, CDKN1B, PRKAR1A, SDHx) or X-linked dominant (GPR101) inheritance are causative of familial pituitary adenomas. Due to variable disease penetrance and occurrence of de novo mutations, some patients harboring germline mutations have no family history of pituitary adenomas (simplex cases). Areas covered: We summarize the recent findings on the role of germline mutations associated with familial pituitary adenomas in patients with sporadic clinical presentation. Expert commentary: Up to 12% of patients with young onset pituitary adenomas (age at diagnosis/onset ≤30 years) and up to 25% of simplex patients with gigantism carry mutations in the AIP gene, while most cases of X-linked acrogigantism (XLAG) due to GPR101 duplication are simplex female patients with very early disease onset (<5 years). With regard to the syndromes of multiple endocrine neoplasia (MEN), MEN1 mutations can be identified in a significant proportion of patients with childhood onset prolactinomas. Somatotroph and lactotroph adenomas are the most common pituitary adenomas associated with germline predisposing mutations. Genetic screening should be considered in patients with young onset pituitary adenomas.

Cancerous leptomeningitis and familial congenital hypopituitarism

People are at higher risk of cancer as they get older or have a strong family history of cancer. The potential influence of environmental and behavioral factors remains poorly understood. Earlier population and case control studies reported that upper quartile of circulating IGF-I is associated with a higher risk of developing cancer suggesting possible involvement of the growth hormone (GH)/IGF system in initiation or progression of cancer. Since GH therapy increases IGF-1 levels, there have been concerns that GH therapy in hypopituitarism might increase the risk of cancer. We report a 42-year-old female patient who presented with subacute onset of symptoms of meningitis and with the absence of fever which resulted in death 70 days after the onset of symptoms. The patient together with her younger brother was diagnosed at the age of 5 years with familial congenital hypopituitarism, due to homozygous mutation c.150delA in PROP1 gene. Due to evolving hypopituitarism, she was replaced with thyroxine (from age 5), hydrocortisone (from age 13), GH (from age 13 until 17), and sex steroids in adolescence and adulthood. Her consanguineous family has a prominent history of malignant diseases. Six close relatives had malignant disease including her late maternal aunt with breast cancer. BRCA 1 and BRCA 2 mutational analysis in the patient's mother was negative. Histology after autopsy disclosed advanced ovarian cancer with multiple metastases to the brain, leptomeninges, lungs, heart, and adrenals. Low circulating IGF-1 did not seem to protect this patient from cancer initiation and progression in the context of strong family history of malignancies.

Histopathology and molecular characterisation of intrauterine-diagnosed congenital craniopharyngioma

PURPOSE

Adamantinomatous craniopharyngiomas (aCPs) are complex epithelial neoplasms that arise from the progenitors of the pituitary gland. Although benign, these tumours can be locally aggressive invading vital neighbouring structures such as the hypothalamus, the cranial and optic nerves. Congenital forms of aCPs diagnosed during foetal development are very rare. The purpose of this article is to present with a histopathological and molecular characterisation of congenital craniopharyngioma.

METHODS

Here we report a case of in utero diagnosed aCP, detected at 21 weeks of gestation by ultrasound, visualised by MRI at 22 weeks and histologically diagnosed at 23 weeks. We provide with histopathological characterisation of rare form of congenital aCPs.

RESULTS

Detailed examination of the tumour reveals the classical histological hallmarks of aCPs with the presence of stellate reticulum, palisading epithelium, wet keratin and calcification deposits. The tumour demonstrated complete absence of all pituitary hormones and the absence of the neuroendocrine marker, synaptophysin. Immunohistochemistry against β-catenin revealed occasional cells with nuclear-β-catenin localisation and the presence of pituitary progenitors positive for SOX9 and SOX2. Targeted Sanger sequencing revealed no genetic variants in oncogenes CTNNB1 and BRAF, previously associated with CP.

CONCLUSIONS

In this article, we provide with in-depth molecular and histological characterisation of in utero aCP due to an unknown driving mutation that could represent a sub-cohort of congenital aCPs.

Excessive growth hormone expression in male GH transgenic mice adversely alters bone architecture and mechanical strength

Patients with acromegaly have a higher prevalence of vertebral fractures despite normal bone mineral density (BMD), suggesting that GH overexpression has adverse effects on skeletal architecture and strength. We used giant bovine GH (bGH) transgenic mice to analyze the effects of high serum GH levels on BMD, architecture, and mechanical strength. Five-month-old hemizygous male bGH mice were compared with age- and sex-matched nontransgenic littermates controls (NT; n=16/group). Bone architecture and BMD were analyzed in tibia and lumbar vertebrae using microcomputed tomography. Femora were tested to failure using three-point bending and bone cellular activity determined by bone histomorphometry. bGH transgenic mice displayed significant increases in body weight and bone lengths. bGH tibia showed decreases in trabecular bone volume fraction, thickness, and number compared with NT ones, whereas trabecular pattern factor and structure model index were significantly increased, indicating deterioration in bone structure. Although cortical tissue perimeter was increased in transgenic mice, cortical thickness was reduced. bGH mice showed similar trabecular BMD but reduced trabecular thickness in lumbar vertebra relative to controls. Cortical BMD and thickness were significantly reduced in bGH lumbar vertebra. Mechanical testing of femora confirmed that bGH femora have decreased intrinsic mechanical properties compared with NT ones. Bone turnover is increased in favor of bone resorption in bGH tibia and vertebra compared with controls, and serum PTH levels is also enhanced in bGH mice. These data collectively suggest that high serum GH levels negatively affect bone architecture and quality at multiple skeletal sites.

Ghrelin

BACKGROUND

The gastrointestinal peptide hormone ghrelin was discovered in 1999 as the endogenous ligand of the growth hormone secretagogue receptor. Increasing evidence supports more complicated and nuanced roles for the hormone, which go beyond the regulation of systemic energy metabolism.

SCOPE OF REVIEW

In this review, we discuss the diverse biological functions of ghrelin, the regulation of its secretion, and address questions that still remain 15 years after its discovery.

MAJOR CONCLUSIONS

In recent years, ghrelin has been found to have a plethora of central and peripheral actions in distinct areas including learning and memory, gut motility and gastric acid secretion, sleep/wake rhythm, reward seeking behavior, taste sensation and glucose metabolism.

Fasting and postprandial liver glycogen content in patients with type 1 diabetes mellitus after successful pancreas-kidney transplantation with systemic venous insulin delivery

BACKGROUND

In patients with type 1 diabetes mellitus (T1DM), insulin is usually replaced systemically (subcutaneously) and not via the physiological portal route. According to previous studies, the liver's capacity to store glycogen is reduced in T1DM patients, but it remains unclear whether this is due to hyperglycaemia, or whether the route of insulin supply could contribute to this phenomenon. T1DM patients after successful pancreas-kidney transplantation with systemic venous drainage (T1DM-PKT) represent a suitable human model to further investigate this question, because they are normoglycaemic, but their liver receives insulin from the pancreas transplant via the systemic route.

MATERIALS AND METHODS

In nine T1DM-PKT, nine controls without diabetes (CON) and seven patients with T1DM (T1DM), liver glycogen content was measured at fasting and after two standardized meals employing (13) C-nuclear-magnetic-resonance-spectroscopy. Circulating glucose and glucoregulatory hormones were measured repeatedly throughout the study day.

RESULTS

The mean and fasting concentrations of peripheral plasma glucose, insulin, glucagon and C-peptide were comparable between T1DM-PKT and CON, whereas T1DM were hyperglycaemic and hyperinsulinaemic (P < 0·05 vs T1DM-PKT and CON). Total liver glycogen content at fasting and after breakfast did not differ in the three groups. After lunch, T1DM-PKT and T1DM had a 14% and 21% lower total liver glycogen content than CON (P < 0·02).

CONCLUSION

In spite of normalized glycaemic control, postprandial liver glycogen content was reduced in T1DM-PKT with systemic venous drainage. Thus, not even optimized systemic insulin substitution is able to resolve the defect in postprandial liver glycogen storage seen in T1DM patients.

Genetic studies in a coexistence of acromegaly, pheochromocytoma, gastrointestinal stromal tumor (GIST) and thyroid follicular adenoma

We report on an adult woman with rare coexistence of acromegaly, pheochromocytoma (PHEO), gastrointestinal stromal tumor (GIST), intestinal polyposis, and thyroid follicular adenoma. At the age of 56, she was diagnosed with acromegaly caused by a pituitary macroadenoma, treated by transsphenoidal surgery, radiotherapy, and octreotide. During routine colonoscopy, multiple polyps were identified as tubular adenomas with high-grade dysplasia on histology. Years later, an abdominal mass of 8.0 x 6.2 cm was detected by routine ultrasound. Surgical exploration revealed an adrenal mass and another tumor adhered to the lesser gastric curvature, which were removed. Pathology confirmed the diagnosis of PHEO and GIST. PHEO immunohistochemistry was negative for GHRH. During follow-up, nodular goiter was found with normal levels of calcitonin and inconclusive cytology. Near-total thyroidectomy was performed, revealing a follicular adenoma. Her family history was negative for all of these tumor types. Genetic analysis for PHEO/paraganglioma genes (SDH A-D, SDHAF2, RET, VHL, TMEM127, and MAX), and pituitary-related genes (AIP, MEN1, and p27) were negative. Though the finding of PHEO and acromegaly with multiple other tumors could be a fortuitous coexistence, we suggest that this case may represent a new variant of MEN syndrome with a de novo germline mutation in a not yet identified gene.

MicroRNAs: Suggested role in pituitary adenoma pathogenesis

MicroRNAs (miRNAs) are small non-coding RNA molecules that represent a major class of molecular regulators. miRNAs have been implicated in the pathogenesis of several human tumors, including pituitary adenomas. Altered expression of miRNAs has been described in pituitary adenomas, and specific miRNA signatures are related to clinical and therapeutic characteristics of the tumors. The data suggest that miRNAs influence various genes known to be associated with the pathogenesis of pituitary adenomas and in this review we summarize these currently available studies focusing on miRNAs in pituitary adenomas.

Familial isolated pituitary adenomas: an emerging clinical entity

Familial pituitary tumors are increasingly recognized. While some of these cases are related to wellknown syndromic conditions such as multiple endocrine neoplasia type 1 (MEN1) or Carney complex, others belong to the familial isolated pituitary adenoma (FIPA) patient group. The discovery of heterozygous, loss-of-function germline mutations in the gene encoding the aryl hydrocarbon receptor interacting protein (AIP) in 2006 has subsequently enabled the identification of a mutation in this gene in 20% of FIPA families and 20% of childhood-onset simplex soma- totroph adenomas. The exact mechanism by which the lack of AIP leads to pituitary adenomas is not clear. AIP mutations cause a low penetrance autosomal dominant disease with often a distinct phenotype characterized by young-onset, aggressive, large GH, mixed GH and PRL or PRL-secreting adenomas. This review aims to summarize currently available clinical data on AIP mutation-positive and negative FIPA patients.

Mice lacking AMP-activated protein kinase α1 catalytic subunit have increased bone remodelling and modified skeletal responses to hormonal challenges induced by ovariectomy and intermittent PTH treatment

AMP-activated protein kinase (AMPK) is a key regulator of cellular and body energy homeostasis. We previously demonstrated that AMPK activation in osteoblasts increases in vitro bone formation while deletion of the Ampkα1 (Prkaa1) subunit, the dominant catalytic subunit expressed in bone, leads to decreased bone mass in vivo. To investigate the cause of low bone mass in the Ampkα1(-/-) mice, we analysed bone formation and resorption in the tibia of these mice by dynamic histomorphometry and determined whether bone turnover can be stimulated in the absence of the Ampkα1 subunit. We subjected 12-week-old Ampkα1(+)(/)(+) and Ampkα1(-/-) mice to ovariectomy (OVX), intermittent PTH (iPTH) administration (80 μg/kg per day, 5 days/week) or both OVX and iPTH hormonal challenges. Tibiae were harvested from these mice and bone micro-architecture was determined by micro-computed tomography. We show for the first time that Ampkα1(-/-) mice have a high bone turnover at the basal level in favour of bone resorption. While both Ampkα1(+)(/)(+) and Ampkα1(-/-) mice lost bone mass after OVX, the bone loss in Ampkα1(-/-) mice was lower compared with controls. iPTH increased trabecular and cortical bone indexes in both ovariectomised Ampkα1(+)(/)(+) and Ampkα1(-/-) mice. However, ovariectomised Ampkα1(-/-) mice showed a smaller increase in bone parameters in response to iPTH compared with Ampkα1(+)(/)(+) mice. By contrast, non-ovariectomised Ampkα1(-/-) mice responded better to iPTH treatment than non-ovariectomised Ampkα1(+)(/)(+) mice. Overall, these data demonstrate that Ampkα1(-/-) mice are less affected by changes in bone turnover induced by OVX but respond better to the anabolic challenge induced by iPTH. These results suggest that AMPKα1 activation may play a role in the hormonal regulation of bone remodelling.

The immunophilin-like protein XAP2 is a negative regulator of estrogen signaling through interaction with estrogen receptor α

XAP2 (also known as aryl hydrocarbon receptor interacting protein, AIP) is originally identified as a negative regulator of the hepatitis B virus X-associated protein. Recent studies have expanded the range of XAP2 client proteins to include the nuclear receptor family of transcription factors. In this study, we show that XAP2 is recruited to the promoter of ERα regulated genes like the breast cancer marker gene pS2 or GREB1 and negatively regulate the expression of these genes in MCF-7 cells. Interestingly, we show that XAP2 downregulates the E₂-dependent transcriptional activation in an estrogen receptor (ER) isoform-specific manner: XAP2 inhibits ERα but not ERβ-mediated transcription. Thus, knockdown of intracellular XAP2 levels leads to increased ERα activity. XAP2 proteins, carrying mutations in their primary structures, loose the ability of interacting with ERα and can no longer regulate ER target gene transcription. Taken together, this study shows that XAP2 exerts a negative effect on ERα transcriptional activity and may thus prevent ERα-dependent events.

The pathology of pituitary adenomas from a clinical perspective

Pituitary adenomas present with a variety of clinical endocrine manifestations and arise in a sporadic setting or rarely as part of hereditary genetic syndromes. Molecular analysis of familial pituitary adenomas has provided significant insight into pituitary tumorigenesis. Some specific genes have been identified that predispose to pituitary neoplasia, but these are rarely involved in the pathogenesis of sporadic tumors. The number of identified genes involved in pituitary tumorigenesis is progressively increasing. The possible resulting mechanisms of action involve abnormalities in signal transduction pathways, cell cycle regulators, growth factors, chromosome stability and others. Further studies are needed to evaluate the clinical significance of genetic alterations and their implications for patient prognosis, as well as to identify targets for existing and new therapeutic options. The aim of this review is to focus on the molecular pathology of pituitary adenomas from a practical perspective and discuss the possible clinical implications which may relate to particular molecular alterations. We have summarised familial syndromes related to pituitary adenomas and considered the prognostic value of selected molecular alterations in these tumors.

AMP-activated protein kinase (AMPK) activation regulates in vitro bone formation and bone mass

Adenosine 5'-monophosphate-activated protein kinase (AMPK), a regulator of energy homeostasis, has a central role in mediating the appetite-modulating and metabolic effects of many hormones and antidiabetic drugs metformin and glitazones. The objective of this study was to determine if AMPK can be activated in osteoblasts by known AMPK modulators and if AMPK activity is involved in osteoblast function in vitro and regulation of bone mass in vivo. ROS 17/2.8 rat osteoblast-like cells were cultured in the presence of AMPK activators (AICAR and metformin), AMPK inhibitor (compound C), the gastric peptide hormone ghrelin and the beta-adrenergic blocker propranolol. AMPK activity was measured in cell lysates by a functional kinase assay and AMPK protein phosphorylation was studied by Western Blotting using an antibody recognizing AMPK Thr-172 residue. We demonstrated that treatment of ROS 17/2.8 cells with AICAR and metformin stimulates Thr-172 phosphorylation of AMPK and dose-dependently increases its activity. In contrast, treatment of ROS 17/2.8 cells with compound C inhibited AMPK phosphorylation. Ghrelin and propranolol dose-dependently increased AMPK phosphorylation and activity. Cell proliferation and alkaline phosphatase activity were not affected by metformin treatment while AICAR significantly inhibited ROS 17/2.8 cell proliferation and alkaline phosphatase activity at high concentrations. To study the effect of AMPK activation on bone formation in vitro, primary osteoblasts obtained from rat calvaria were cultured for 14-17days in the presence of AICAR, metformin and compound C. Formation of 'trabecular-shaped' bone nodules was evaluated following alizarin red staining. We demonstrated that both AICAR and metformin dose-dependently increase trabecular bone nodule formation, while compound C inhibits bone formation. When primary osteoblasts were co-treated with AICAR and compound C, compound C suppressed the stimulatory effect of AICAR on bone nodule formation. AMPK is a alphabetagamma heterotrimer, where alpha is the catalytic subunit. RT-PCR analysis of AMPK subunits in ROS17/2.8 osteoblastic cells and in mouse tibia showed that the AMPKalpha1 subunit is the dominant isoform expressed in bone. We analysed the bone phenotype of 4month-old male wild type (WT) and AMPKalpha1-/- KO mice using micro-CT. Both cortical and trabecular bone compartments were smaller in the AMPK alpha1-deficient mice compared to the WT mice. Altogether, our data support a role for AMPK signalling in skeletal physiology.