Damian G. Morris

The medical management of Cushing's syndrome.

Abstract: Cushings syndrome results from prolonged exposure to excessive circulating glucocorticosteroids, and is associated with significant morbidity and mortality. While the treatment of choice in most patients is surgical, the metabolic consequences of the syndrome, including increased tissue fragility, poor wound healing, hypertension, and diabetes mellitus, increase the risks of such surgery. The hypercortisolemia and its sequelae can be efficiently reversed using medical therapy, either as a temporary measure prior to definitive treatment, or longer term in more difficult cases. Drug treatment has been targeted at the hypothalamic/pituitary level, the adrenal glands, and also at the glucocorticoid receptor level. In this review we discuss the pharmacotherapeutic agents that have been used in Cushings syndrome, and their efficacy, the monitoring of treatment, and potential therapies that may prove useful in the future in this complex endocrinological disorder.

Heterogeneous Genetic Background of the Association of Pheochromocytoma/Paraganglioma and Pituitary Adenoma: Results From a Large Patient Cohort

Context: Pituitary adenomas and pheochromocytomas/paragangliomas (pheo/PGL) can occur in the same patient or in the same family. Coexistence of the two diseases could be due to either a common pathogenic mechanism or a coincidence. Objective: The objective of the investigation was to study the possible coexistence of pituitary adenoma and pheo/PGL. Design: Thirty-nine cases of sporadic or familial pheo/PGL and pituitary adenomas were investigated. Known pheo/PGL genes (SDHA-D, SDHAF2, RET, VHL, TMEM127, MAX, FH) and pituitary adenoma genes (MEN1, AIP, CDKN1B) were sequenced using next generation or Sanger sequencing. Loss of heterozygosity study and pathological studies were performed on the available tumor samples. Setting: The study was conducted at university hospitals. Patients: Thirty-nine patients with sporadic of familial pituitary adenoma and pheo/PGL participated in the study. Outcome: Outcomes included genetic screening and clinical characteristics. Results: Eleven germline mutations (five SDHB, one SDHC, one SDHD, two VHL, and two MEN1) and four variants of unknown significance (two SDHA, one SDHB, and one SDHAF2) were identified in the studied genes in our patient cohort. Tumor tissue analysis identified LOH at the SDHB locus in three pituitary adenomas and loss of heterozygosity at the MEN1 locus in two pheochromocytomas. All the pituitary adenomas of patients affected by SDHX alterations have a unique histological feature not previously described in this context. Conclusions: Mutations in the genes known to cause pheo/PGL can rarely be associated with pituitary adenomas, whereas mutation in a gene predisposing to pituitary adenomas (MEN1) can be associated with pheo/PGL. Our findings suggest that genetic testing should be considered in all patients or families with the constellation of pheo/PGL and a pituitary adenoma.

Sequence analysis of the PRKAR1A gene in sporadic somatotroph and other pituitary tumours

objective Carney complex (CNC) is an autosomal dominant multiple neoplasia syndrome featuring cardiac, endocrine, cutaneous and neural tumours, as well as a variety of pigmented lesions of the skin and mucosa. Pituitary GH‐secreting tumours are found in approximately 10% of patients with CNC. One of the genes responsible for CNC, the PRKAR1A gene located on human chromosome 17q22‐24, has recently been cloned. This represents a putative tumour suppressor gene, coding for the type 1α regulatory subunit of protein kinase A (PKA), which is found to be mutated in approximately half of the patients with CNC. However, it is currently unclear as to whether similar mutations occur in sporadic pituitary tumours. We have therefore investigated a series of GH‐secreting and other pituitary tumours for sequence abnormalities in the PRKAR1A gene. The mRNA produced by the PRKAR1A undergoes decay if it codes for a truncated protein; we therefore also determined PRKAR1A mRNA levels in the tumours, and compared them with known mutant PRKAR1A‐carrying lymphocyte samples.

Reduced expression of the growth hormone and type 1 insulin‐like growth factor receptors in human somatotroph tumours and an analysis of possible mutations of the growth hormone receptor

objective Clinical acromegaly is characterized by elevated GH secretion in the presence of high circulating IGF‐I levels. We hypothesized that the physiological IGF‐I/GH negative feedback loop may be reset in somatotroph adenomas, specifically in terms of the level of expression of these receptors or mutations of the GH receptor (GH‐R) in such tumours.

Role of Regulatory Factors in Pituitary Tumour Formation

The molecular basis of pituitary tumorigenesis remains controversial, but there are two major theories which have been subject to most investigation: hormonal (usually hypothalamic factors) and/or growth factor overstimulation, or a molecular defect within the pituitary itself. It has been shown, for example, that excessive regulatory hormone stimulation can lead to an increased number of cells in the pituitary in various physiological or pathological states such as pregnancy (lactotrophs), untreated primary hypothyroidism (thyrotrophs and lactotrophs),primary hypoadrenalism (corticotrophs) and ectopic GHRH-secreting tumours (somatotrophs). Animal models also provide data that in the presence of excessive hypothalamic hormone stimulation, adenoma formation can occur. However, evidence in favour of the monoclonal nature of pituitary tumours argues for an intrinsic molecular defect as the primary initiating event in tumour formation. We review the various hormonal factors and their receptors effecting the different types of pituitary cells, such as CRH, AVP and cortisol feedback on corticotrophs; GHRH, Galpha PKA, somatostatin and GH and IGF feedback on somatotrophs; GnRH, LH/FSH, activin and oestrogen feedback on gonadotrophs; dopamine, oestrogen and prolactin feedback on lactotrophs; and TRH, TSH and thyroid hormone feedback on thyrotrophs. The monoclonal origin of adenomas makes it unlikely that hypothalamic factors could initiate pituitary transformation, but they could still create an environment where there is a higher chance that a possible causative tumorigenic mutation may occur in one (or several) of the overstimulated pituitary cells, or enhance the proliferation of an already-mutated cell.

The Expression of the F-Box Protein Skp2 is Negatively Associated with p27 Expression in Human Pituitary Tumors

The CDK inhibitor p27 plays a pivotal role in controlling cell proliferation during development, and has been implicated in tumorigenesis. Previous studies have demonstrated changes in p27 protein expression, but not in mRNA levels, in human pituitary tumors. It seems probable that the fall in p27 is due to increased degradation through the ubiquitin-proteasome pathway. Skp2 (S-phase kinase-interacting protein) is a specific F-box protein that allows the recognition and binding of phosphorylated p27 to the ubiquitin complex. The aim of our study was thus to investigate the possible role of Skp2 in pituitary tumorigenesis.A total of 59 human pituitary samples, 7 normal and 52 adenomas, were assessed for transcriptional expression of Skp2; 51 pituitary samples were assessed for protein expression. Real-time RT-PCR was performed on cDNA of reverse-transcribed mRNA for relative quantification of the Skp2 transcript. Immunostaining was performed using mouse monoclonal anti-Skp2 antibody.Skp2 mRNA and protein was detectable in every sample studied. Our results showed no significant difference between the pituitary tumors and normal pituitary tissue in Skp2 mRNA or nuclear protein expression. Individual tumor types had similar mRNA expression and variable protein expression. However, samples with high p27 protein expression showed significantly less Skp2 expression than samples with low p27 staining.Our data suggest that increased p27 degradation through the ubiquitin-proteasome pathway could be regulated in pituitary tumors by changes in Skp2 expression, although other factors probably also play a role.

Cyclins and their related proteins in pituitary tumourigenesis.

Pituitary tumours are benign neoplasms that may cause major endocrine dysfunction. Transgenic disruption of the cell cycle machinery frequently leads to pituitary adenoma formation in animal models. The molecular analysis of human pituitary tumours has found various alterations in the expression of cell cycle regulators: cyclins, cyclin-dependent kinases and their inhibitors. There are also different mechanisms (e.g. hypermethylation, frameshift mutations, increased proteasome degradation) responsible for changed expression in cyclin mRNA and protein. It is probable that the primary initiating events lie beyond the cell cycle and may be related to co-activation of Akt, MAP-kinase and beta-catenin pathways. Nevertheless, molecular CDK inhibitors may play a role in pituitary tumour treatment in the future.

Successful treatment of residual pituitary adenoma in persistent acromegaly following localisation by 11C-methionine PET co-registered with MRI

OBJECTIVE To determine if functional imaging using 11C-methionine positron emission tomography co-registered with 3D gradient echo MRI (Met-PET/MRI), can identify sites of residual active tumour in treated acromegaly, and discriminate these from post-treatment change, to allow further targeted treatment. DESIGN/METHODS Twenty-six patients with persistent acromegaly after previous treatment, in whom MRI appearances were considered indeterminate, were referred to our centre for further evaluation over a 4.5-year period. Met-PET/MRI was performed in each case, and findings were used to decide regarding adjunctive therapy. Four patients with clinical and biochemical remission after transsphenoidal surgery (TSS), but in whom residual tumour was suspected on post-operative MRI, were also studied. RESULTS Met-PET/MRI demonstrated tracer uptake only within the normal gland in the four patients who had achieved complete remission after primary surgery. In contrast, in 26 patients with active acromegaly, Met-PET/MRI localised sites of abnormal tracer uptake in all but one case. Based on these findings, fourteen subjects underwent endoscopic TSS, leading to a marked improvement in (n = 7), or complete resolution of (n = 7), residual acromegaly. One patient received stereotactic radiosurgery and two patients with cavernous sinus invasion were treated with image-guided fractionated radiotherapy, with good disease control. Three subjects await further intervention. Five patients chose to receive adjunctive medical therapy. Only one patient developed additional pituitary deficits after Met-PET/MRI-guided TSS. CONCLUSIONS In patients with persistent acromegaly after primary therapy, Met-PET/MRI can help identify the site(s) of residual pituitary adenoma when MRI appearances are inconclusive and direct further targeted intervention (surgery or radiotherapy).