Medical therapy of pituitary adenomas: effects on tumor shrinkage

The efficacy and safety of quinagolide in hyperprolactinemia treatment: A systematic review and meta-analysis

PURPOSE

Three dopamine agonists [bromocriptine, cabergoline, and quinagolide (CV)] have been used for hyperprolactinemia treatment for decades. Several studies have reviewed the efficacy and safety of bromocriptine and cabergoline. However, no systematic review or meta-analysis has discussed the efficacy and safety of CV in hyperprolactinemia and prolactinoma treatment.

METHODS

Five medical databases (PubMed, Web of Science, Embase, Scopus, and Cochrane Library) were searched up to 9 May 2022 to identify studies related to CV and hyperprolactinemia. A meta-analysis was implemented by using a forest plot, funnel plot, sensitivity analysis, meta-regression, and Egger's test via software R 4.0 and STATA 12.

RESULTS

A total of 1,211 studies were retrieved from the five medical databases, and 33 studies consisting of 827 patients were finally included in the analysis. The pooled proportions of patients with prolactin concentration normalization and tumor reduction (>50%) under CV treatment were 69% and 20%, respectively, with 95% confidence intervals of 61%-76% and 15%-28%, respectively. The pooled proportion of adverse effects was 13%, with a 95% confidence interval of 11%-16%.

CONCLUSION

Our study showed that CV is not less effective than cabergoline and bromocriptine in treating hyperprolactinemia, and the side effects were not significant. Hence, this drug could be considered an alternative first-line or rescue treatment in treating hyperprolactinemia in the future.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO, identifier CRD42022347750.

Current medical treatment and perspective in gonadotroph tumors

Gonadotroph cell adenoma is the most common clinically nonfunctioning pituitary adenoma; and is pathologically defined by immunopositivity for SF-1, GATA2 and ER-α. Most tumors also stain for follicle stimulating hormone and luteinizing hormone β-subunits, but are usually hormonally silent and discovered incidentally or due to local mass effects. Complete transsphenoidal resection should be attempted when surgery is indicated. Post-surgical treatment can include radiation of the tumor remnant and medical treatment. Among medical treatments, dopamine agonists show the best evidence for preventing the need for recurrent surgery or radiation, and should be considered in patients with relatively bulky remnants or who have high risk features associated with tumor progression. Temozolomide is indicated for aggressive adenomas and carcinomas. Less well-established treatments include somatostatin receptor ligands, peptide receptor radionucleotide therapy and immunomodulatory agents.

Hyperprolactinemia after menopause: Diagnosis and management

Most prolactinomas are diagnosed in women of reproductive age and are generally microadenomas. Prolactinomas diagnosed in postmenopausal women are less common and are not usually associated with the typical syndrome induced by prolactin excess, including infertility and oligo-amenorrhea. This implies that the diagnosis of prolactinomas after menopause may be delayed and require greater clinical effort. Limited data are available on the management and prognosis of prolactinomas in postmenopausal women. However, the physiologic decline of prolactin levels during menopause and the lack of fertility concerns, which represent specific indications for medical treatment with dopamine agonists, might require a careful reassessment of therapeutic management in such patients. Postmenopausal women with microprolactinoma may be successfully withdrawn from medical therapy with dopamine agonists, whereas in those with macroprolactinomas greater caution is advisable before dopamine agonists are discontinued, considering the potential, although rare, tumor enlargement. This review focuses on the diagnostic challenges and therapeutic management of prolactinomas in postmenopausal women.

Pituitary Adenomas: From Diagnosis to Therapeutics

Pituitary adenomas are tumors that arise in the anterior pituitary gland. They are the third most common cause of central nervous system (CNS) tumors among adults. Most adenomas are benign and exert their effect via excess hormone secretion or mass effect. Clinical presentation of pituitary adenoma varies based on their size and hormone secreted. Here, we review some of the most common types of pituitary adenomas, their clinical presentation, and current diagnostic and therapeutic strategies.

Somatostatin Analogs in Clinical Practice: a Review

Somatostatin analogs are an invaluable therapeutic option in the diagnosis and treatment of somatotropinomas, thyrotropinomas, and functioning and non-functioning gastroenteropancreatic neuroendocrine tumors. They should also be considered an effective and safe therapeutic alternative to corticotropinomas, gonadotropinomas, and prolactinomas resistant to dopamine agonists. Somatostatin analogs have also shown to be useful in the treatment of other endocrine diseases (congenital hyperinsulinism, Graves’ orbitopathy, diabetic retinopathy, diabetic macular edema), non-endocrine tumors (breast, colon, prostate, lung, and hepatocellular), and digestive diseases (chronic refractory diarrhea, hepatorenal polycystosis, gastrointestinal hemorrhage, dumping syndrome, and intestinal fistula).

Body self-image disturbances in women with prolactinoma

Objective:

To evaluate body dissatisfaction and distorted body self-image in women with prolactinoma.

Methods:

Body dissatisfaction and distorted body self-image were evaluated in 80 women with prolactinoma. All patients were in menacme, 34% had normal body mass index (BMI), and 66% were overweight. Most patients (56.2%) had normal prolactin (PRL) levels and no hyperprolactinemia symptoms (52.5%). The Body Shape Questionnaire (BSQ) was used to assess the patients’ dissatisfaction with and concern about their physical form, and the Stunkard Figure Rating Scale (FRS) was used to assess body dissatisfaction and distorted body self-image. The patients were divided according to PRL level (normal vs. elevated) and the presence or absence of prolactinoma symptoms.

Results:

The normal and elevated PRL groups had similar incidences of body dissatisfaction and distorted body self-image. However, symptomatic patients reported a higher incidence of dissatisfaction than asymptomatic patients. Distorted body self-image was less common among symptomatic patients.

Conclusion:

Symptomatic patients showed higher body dissatisfaction, but lower body self-image distortion. The presence of symptoms may have been responsible for increased body awareness. The perception of body shape could have triggered feelings of dissatisfaction compared to an ideal lean body. Therefore, a distorted body self-image might not necessarily result in body dissatisfaction in women with prolactinomas.

Thyrotropin-secreting pituitary adenomas: a systematic review and meta-analysis of postoperative outcomes and management

PURPOSE

TSH-secreting pituitary adenomas are rare pituitary tumors. An efficient treatment is essential to limit the mortality and morbidity in untreated patients. The aim of this study is to summarize the evidence about the postoperative outcomes and management of this rare pathology.

METHODS

A systematic search and meta-analysis of surgical series was performed.

RESULTS

Our analysis included 23 articles (536 patients). No sex difference was observed and mean age at diagnosis was 45 years. Hyperthyroidism was reportedly clinical in 67% and biochemical in 90% of patients. Co-secretion of other pituitary hormones was present in 42% of cases. Macroadenomas were found in 79% of patients, showing in 44% and 30% of cases respectively extrasellar extension and cavernous sinus invasion. The pooled rate of postoperative biochemical remission was 69.7% and a gross total resection (GTR) was observed in 54% of patients. The extent of resection was significantly increased in microadenomas (p < 0.001) and cavernous sinus invasion was predictive of lower GTR rate (p < 0.001). A biochemical remission was achieved in 66% of patients after adjuvant radiation therapy and in 76% after adjuvant medical treatment. The combination of both allowed remission in 67% of cases. At final follow-up the overall biochemical remission rate was significantly improved (85.8%) when compared to the postoperative biochemical remission (p < 0.001).

CONCLUSION

When compared to the early postoperative period, at last follow-up biochemical remission was significantly greater (p < 0.001). GTR was achieved in half of patients; the size of tumor and cavernous sinus invasion determined the extent of resection.

Surgery for Prolactinomas to Date

While in the past surgery for prolactinomas was a competitive option to medical treatment with dopamine agonists, to date the indications for operations are restricted to only a few specific situations. However, if a patient is intolerant to medical treatment or if the drugs are not sufficiently effective in terms of lowering prolactin levels or tumor shrinkage, surgery should always be considered. In microprolactinomas, operations can achieve excellent prolactin normalization rates. In tumors difficult to treat, the combination of surgical tumor resection and long-term medical treatment supports better control of the disease. The individual indications, results, techniques, and complications of operations for prolactinomas are briefly reviewed in this paper.

Effect of combined treatment with a pan-PI3K inhibitor or an isoform-specific PI3K inhibitor and everolimus on cell proliferation in GH-secreting pituitary tumour in an experimental setting

PURPOSE

PI3K/Akt/mTOR pathway activation is common in GH-secreting pituitary tumours, and a target for treatment with mTOR inhibitors, including everolimus (EVE). The current study aimed to evaluate the efficacy of two PI3K inhibitors (PI3Ki), NVP-BKM120 and NVP-BYL719, alone and in combination with EVE in rat GH-secreting pituitary tumour cell line (GH3) and human GH-secreting pituitary tumour cell cultures.

METHODS

In GH3 cell line and in six GH-secreting tumour cell cultures, the effects of PI3Ki and EVE, as single agents and in combination, were tested on cell viability and colony survival, by MTT and clonogenic assay, respectively, whereas western blot was performed to evaluate the underlying intracellular signalling pathways.

RESULTS

PI3Ki and EVE showed a dose-dependent inhibition of cell viability in GH3 cell line, with PI3Ki displaying a synergistic effect when combined with EVE. PI3Ki and EVE inhibited colony survival in GH3 cell line with no further improvement in combination. In GH-secreting pituitary tumour cell cultures PI3Ki are effective in inhibiting cell viability increasing the slight and non significant inhibition induced by EVE as single agent, generally showing a synergistic effect. Despite in both GH3 cell line and GH-secreting pituitary tumour cell cultures combination of PI3Ki enhanced EVE effect, the study of intracellular signalling pathways revealed a different regulation of PI3K/Akt/mTOR and MAPK between the two models.

CONCLUSIONS

The results of the current study demonstrated that PI3Ki, especially in combination with EVE, are effective in inhibiting cell proliferation, therefore representing a promising therapeutic tool for the treatment of aggressive GH-secreting pituitary tumours, not responsive to standard medical therapies.

Cabergoline versus bromocriptine for the treatment of giant prolactinomas: A quantitative and systematic review

The aim of this study is to compare the efficacy of bromocriptine (BRC) versus cabergoline (CAB) in patients with giant prolactinomas. We searched MEDLINE, EMBASE, CENTRAL and Clinical Trials.gov for studies dated before March 1st, 2016, that used BRC or CAB for the treatment of patients with giant prolactinomas. Specific eligibility criteria were set to identify articles and cases. The selected articles were reviewed, and the data were extracted for analysis. The compared outcomes included tumor shrinkage, tumor response, normalization of prolactin (PRL) level, and visual field defect (VFD) improvement. Gender differences were also considered. Differences between the groups were assessed using Student's t test and the chi-square test. Two hundred and forty-five records were identified, and 10 articles and 104 cases met the inclusion criteria. Based on our analysis, CAB is significantly better than BRC in normalizing PRL levels in patients, especially males, with giant prolactinomas (69.4% versus 31.7%, p = 0.01). However, there was no significant difference between the two drugs in terms of tumor shrinkage, tumor response and VFD improvement (p > 0.05) in male or female patients. CAB exhibits significantly better efficacy than BRC in the normalization of PRL levels in male patients with giant prolactinomas. Regarding tumor reduction and VFD improvement, both drugs are comparably effective for patients of both genders. This quantitative and systematic review provides preliminary evidence in favor of CAB as a medical therapy for treating giant prolactinomas in male patients, especially those with extremely high PRL levels.

Management of NFAs: medical treatment

INTRODUCTION

Non-functioning pituitary adenomas (NFPAs) are in general large tumors that present with symptoms secondary to local pressure on adjacent structures. Transsphenoidal surgery is the first line of treatment but residual tumor mass is often detected post-operatively. Medical therapy, in any stage of tumor management, is not well established.

METHODS

A literature search was performed to review the available data on medical treatment of NFPAs.

RESULTS

Medications investigated for the treatment of NFPAs include dopamine receptor agonists (DA) and somatostatin receptor ligands. Randomized controlled trials are lacking, but available data suggest that DA have a positive effect on tumor remnant stabilization after surgery and could be considered in this setting. Temozolomide is reserved for aggressive tumors, although future studies are required.

CONCLUSIONS

NFPA are often not amenable to complete surgical resection. Conservative follow-up after surgery is associated with a high prevalence of tumor remnant progression. DA therapy may prevent residual tumor enlargement in over 85% of these patients, with a substantial consequent reduction in the need for repeat surgery or radiation therapy. It is our view that DA treatment should be routinely considered for the management of NFPA patients with incompletely resected tumors.

DIAGNOSIS OF ENDOCRINE DISEASE: Diagnostic approach to TSH-producing pituitary adenoma

Thyrotropin (TSH)-secreting adenomas (TSHomas) are the rarest form of pituitary adenomas, and most endocrinologists will see few cases in a lifetime, if any. In most cases, the diagnostic approach is complicated and cases may be referred after being presented as a syndrome of inappropriate TSH secretion or as a pituitary mass. This review aims to cover the past, present and possible future diagnostic approaches to TSHomas, including different clinical presentations, laboratory assessment and imaging advances. The differential diagnoses will be discussed, as well as possible coexisting disorders. By evaluating the existing reports and reviews describing this rare condition, this review aims to present a clinically practical suggestion on the diagnosic workup for TSHomas, Major advances and scientific breakthroughs in the imaging area in recent years, facilitating diagnosis of TSHomas, support the belief that future progress within the imaging field will play an important role in providing methods for a more efficient diagnosis of this rare condition.

Notch system is differentially expressed and activated in pituitary adenomas of distinct histotype, tumor cell lines and normal pituitaries

Pituitary adenomas are among the most frequent intracranial neoplasms and treatment depends on tumor subtype and clinical features. Unfortunately, non responder cases occur, then new molecular targets are needed.

Notch system component expression and activation data are scarce in pituitary tumorigenesis, we therefore aimed to characterize Notch system in pituitary tumors of different histotype. In human pituitary adenomas we showed NOTCH1-4 receptors, JAGGED1 ligand and HES1 target gene expression with positive correlations between NOTCH1,2,4 and HES1, and NOTCH3 and JAGGED1 denoting Notch system activation in a subset of tumors. Importantly, NOTCH3 positive cells were higher in corticotropinomas and somatotropinomas compared to non functioning adenomas. In accordance, Notch activation was evidenced in AtT20 tumor corticotropes, with higher levels of NOTCH1-3 active domains, Jagged1 and Hes1 compared to normal pituitary.

In the prolactinoma cell lines GH3 and MMQ, in vivo GH3 tumors and normal glands, Notch system activation was lower than in corticotropes. In MMQ cells only the NOTCH2 active domain was increased, whereas NOTCH1 active domain was higher in GH3 tumors. High levels of Jagged1 and Dll1 were found solely in GH3 cells, and Hes1, Hey1 and Hey2 were expressed in a model dependent pattern.

Prolactinomas harbored by lacDrd2KO mice expressed high levels of NOTCH1 active domain and reduced Hes1.

We show a differential expression of Notch system components in tumoral and normal pituitaries and specific Notch system involvement depending on adenoma histotype, with higher activation in corticotropinomas. These data suggest that targeting Notch pathway may benefit non responder pituitary adenomas.

Low expression of secreted frizzled-related protein 2 and nuclear accumulation of β-catenin in aggressive nonfunctioning pituitary adenoma

The identification of a specific molecular marker for aggressiveness of nonfunctioning pituitary adenomas (NFPAs) is urgently required in order to guide the clinical diagnosis and treatment of NFPAs. In the present study, low expression of secreted frizzled-related protein 2 (sFRP2) in NFPAs was demonstrated by reverse transcription-quantitative polymerase chain reaction, western blot and immunohistochemical analyses. The results confirmed an abnormal accumulation of free β-catenin in the nuclei of NFPAs, which is the core step for the activation of the Wnt canonical signaling pathway. Furthermore, cyclin D1 and c-Myc, the downstream proteins of the Wnt canonical signaling pathway, were overexpressed in aggressive NFPAs. These findings demonstrated the activation of the Wnt canonical signaling pathway in aggressive NFPAs. In addition, sFRP2 expression was observed to be inversely correlated to the aggressiveness of NFPAs. Therefore, sFRP2 may act as a tumor suppressor through modulation of the cellular cytosolic pool of β-catenin in NFPAs. Furthermore, the expression of sFRP2 may serve as a biomarker for NFPAs aggressiveness and prognosis.

Research Resource: Real-Time Analysis of Somatostatin and Dopamine Receptor Signaling in Pituitary Cells Using a Fluorescence-Based Membrane Potential Assay

Stable somatostatin analogues and dopamine receptor agonists are the mainstay for the pharmacological treatment of functional pituitary adenomas; however, only a few cellular assays have been developed to detect receptor activation of novel compounds without disrupting cells to obtain the second messenger content. Here, we adapted a novel fluorescence-based membrane potential assay to characterize receptor signaling in a time-dependent manner. This minimally invasive technique provides a robust and reliable read-out for ligand-induced receptor activation in permanent and primary pituitary cells. The mouse corticotropic cell line AtT-20 endogenously expresses both the somatostatin receptors 2 (sst2) and 5 (sst5). Exposure of wild-type AtT-20 cells to the sst2- and sst5-selective agonists BIM-23120 and BIM-23268, respectively, promoted a pertussis toxin- and tertiapin-Q-sensitive reduction in fluorescent signal intensity, which is indicative of activation of G protein-coupled inwardly rectifying potassium (GIRK) channels. After heterologous expression, sst1, sst3, and sst4 receptors also coupled to GIRK channels in AtT-20 cells. Similar activation of GIRK channels by dopamine required overexpression of dopamine D2 receptors (D2Rs). Interestingly, the presence of D2Rs in AtT-20 cells strongly facilitated GIRK channel activation elicited by the sst2-D2 chimeric ligand BIM-23A760, suggesting a synergistic action of sst2 and D2Rs. Furthermore, stable somatostatin analogues produced strong responses in primary pituitary cultures from wild-type mice; however, in cultures from sst2 receptor-deficient mice, only pasireotide and somatoprim, but not octreotide, induced a reduction in fluorescent signal intensity, suggesting that octreotide mediates its pharmacological action primarily via the sst2 receptor.

Expression profiles of somatostatin, dopamine, and estrogen receptors in pituitary adenomas determined by means of synthetic multilocus calibrators

AIMS

Pituitary adenomas (PA) are non-invasive benign tumors with a high autopsy prevalence. They are classified according to the type of hormone secreted (prolactin, growth hormone, adrenocorticotropin, thyrotropin, folitropin, or luteinizing hormone). Clinically non-functioning adenomas (CNFA) lacking the typical hypersecretion of hormones make up a significant portion of PA. The aim of the study was to determine the complete expression profiles of somatostatin receptors (SSTR1-SSTR5), dopamine receptors type 2 (D2R), and estrogen receptors (ER1) in various types of PA.

METHODS

Adenoma specimens were obtained from 206 patients during transsphenoidal resection. For quantitative analysis, reverse transcription and consequent real-time PCR with synthetic multilocus calibrators (SMC) were used. The obtained data were normalized to the number of transcripts of the beta-glucuronidase gene.

RESULTS

The use of SMC enabled the alignment of individual calibration functions for all the receptors. No relationships between the expression of the receptors and the tumor size, site of extension, gender or age at diagnosis were significant. In growth hormone-secreting adenomas, D2R and SSTR2 transcripts were extensively expressed, followed by ER1, SSTR5, SSTR3, and SSTR1. In patients with macroprolactinomas, transsphenoidal resection was indicated because dopamine agonists did not normalize prolactin levels. D2R, ER1 and SSTR1 transcripts were significantly transcribed. Corticotroph adenomas showed high levels of D2R and ER1 transcripts and lower amounts of SSTR2 and SSTR1 transcripts. SSTR5 transcripts were very low. Subjects with CNFA dominantly expressed D2R and ER1, followed by SSTR2 and SSTR3 mRNA.

CONCLUSION

We evaluated SSTR1-SSTR5, D2R, and ER1 expressions in a large group of pituitary adenomas and we found that determining their individual expression profiles could help when choosing the optimal postoperative treatment.

Complications following primary and revision transsphenoidal surgeries for pituitary tumors

OBJECTIVES/HYPOTHESIS

This study aimed to determine the incidence of major complications following both primary and revision transsphenoidal pituitary surgery. Major complications included endocrinopathic, skull base, orbital, hemorrhagic and thromboembolic complications, respiratory failure, and death. Secondarily, this study aimed to examine factors associated with the occurrence of complications.

STUDY DESIGN

Retrospective cohort analysis of California and Florida all-payer databases from 2005 to 2008.

METHODS

The major complication rate following both primary and revision transsphenoidal pituitary surgery was calculated. Bivariate analyses were performed to investigate the relationship of patient characteristics with complication occurrence, and a multivariate model was constructed to determine risk factors associated with these complications.

RESULTS

There were 5,277 primary cases and 192 revision cases that met inclusion criteria. There was a nonsignificant absolute difference of 3.09% (95% confidence interval [CI]: -11.00 to 16.14) between the rate of complications following primary (n = 443, 8.39%) and revision (n = 22, 11.46%) surgeries. Multivariate analyses showed that patients with Medicare (odds ratio [OR]:1.74, 95% CI: 1.17 to 2.61), Medicaid (OR: 2.13, 95% CI: 1.59 to 2.86), or a malignant neoplasm (OR: 3.10, 95% CI: 1.62 to 5.93) were more likely to have complications.

CONCLUSIONS

The rate of major complications following transsphenoidal pituitary surgery is lower than earlier retrospective reports. The overall complication rate following revision surgery was not significantly different from primary surgery. Insurance status and a diagnosis of a malignant neoplasm were associated with a higher rate of complications.

LEVEL OF EVIDENCE

2C.

Somatostatin system: molecular mechanisms regulating anterior pituitary hormones

The somatostatin (SRIF) system, which includes the SRIF ligand and receptors, regulates anterior pituitary gland function, mainly inhibiting hormone secretion and to some extent pituitary tumor cell growth. SRIF-14 via its cognate G-protein-coupled receptors (subtypes 1-5) activates multiple cellular signaling pathways including adenylate cyclase/cAMP, MAPK, ion channel-dependent pathways, and others. In addition, recent data have suggested SRIF-independent constitutive SRIF receptor activity responsible for GH and ACTH inhibition in vitro. This review summarizes current knowledge on ligand-dependent and independent SRIF receptor molecular and functional effects on hormone-secreting cells in the anterior pituitary gland.

The expression profile of Dopamine D2 receptor, MGMT and VEGF in different histological subtypes of pituitary adenomas: a study of 197 cases and indications for the medical therapy

BACKGROUND

To study the expression of D2R, MGMT and VEGF for clinical significance in pituitary adenomas, and to predict the potential curative medical therapy of dopamine agonists, temozolomide and bevacizumab on pituitary adenomas.

METHODS

Immunohistochemistry and western blot were performed to detect the expression of expression of D2R, MGMT and VEGF in pituitary adenoma tissue samples. The ratio of high expression of D2R, MGMT or VEGF in different subtypes of PA was compared by the use of chi-squared tests. The relationships between D2R, MGMT and VEGF expression were assessed by the Spearman rank correlation test. The association between their expression and clinical parameters was analyzed using a chi-squared test, or Fisher's exact probability test when appropriate.

RESULTS

The data showed that in 197 different histological subtypes of pituitary adenomas (PAs), 64.9% of them were D2R high expression, 86.3% were MGMT low expression and 58.9% were VEGF high expression. D2R high expression existed more frequently in PRL- and GH- secreting PAs. MGMT low expression existed in all PA subtypes. VEGF high expression existed more frequently in PRL, ACTH, FSH secreting and non-functioning PAs. The data of western blot also support the results. Spearman's rank correlation analysis showed that expression of MGMT was positively associated with D2R (r = 0.154, P = 0.031) and VEGF (r = 0.161, P = 0.024) in PAs, but no correlation was showed between D2R and VEGF expression (r = -0.025, P = 0.725 > 0.05). The association between their expression and clinical parameters was analyzed using a chi-squared test, or Fisher's exact probability test when appropriate, but the result showed no significant association.

CONCLUSIONS

PRL-and GH-secreting PAs exist high expression of D2R, responding to dopamine agonists; Most PAs exist low expression of MGMT and high expression of VEGF, TMZ or bevacizumab treatment could be applied under the premise of indications.

ZAC1 and SSTR2 are downregulated in non-functioning pituitary adenomas but not in somatotropinomas

Introduction

There are few data regarding ZAC1 expression in clinically non-functioning pituitary adenomas (NFPA). Because somatotropinomas and NFPA behave differently with respect to tumor shrinkage during somatostatin analogs (SA) therapy, we sought to compare the ZAC1 and somatostatin receptor (sstr) types 1, 2, 3 and 5 mRNA expression in these two pituitary adenoma subtypes and in normal human pituitaries.

Methods

ZAC1 and SSTR mRNA expression levels were evaluated using real-time RT-PCR (TaqMan) in 20 NFPA and compared with the expression levels in 23 somatotropinomas and five normal pituitaries. The NFPA invasiveness was evaluated using magnetic resonance imaging with Hardy’s modified criteria. Ki-67 and p53 were evaluated using immunohistochemistry.

Results

A total of 20 patients with NFPA [6 males, median age 56 years (range: 30-78)], 23 with acromegaly [12 males, median age 43 years (range: 24–57)] and five normal pituitaries [4 males, median age 48 years (range: 36–54)] were included. Four of the patients (20%) had Hardy’s grade 2 tumors; all of the others had Hardy’s grade 3 tumors. The Ki-67 median expression was 2.35 (range: 0.2–9.23), and only four of the tumors (20%) were positive for p53. The ZAC1 mRNA expression was significantly lower in NFPA than in somatotropinomas and in normal pituitaries (p<0.001 for both), as well as the SSTR2 (p=0.001 and 0.01, respectively). The SSTR3 expression was higher in the NFPA than in the somatotropinomas and in the normal pituitaries (p=0.03 and 0.02, respectively). No correlation was found between the ZAC1 mRNA expression and the tumor invasiveness, Ki-67 and p53.

Conclusion

ZAC1 and SSTR2 are underexpressed and SSTR3 is overexpressed in NFPA compared to those in somatotropinomas and in normal pituitaries, which might explain the lack of tumor shrinkage that is observed in response to commercially available SA therapy in patients with NFPA.

Overexpression of the Notch3 receptor and its ligand Jagged1 in human clinically non-functioning pituitary adenomas

Human clinically non-functioning pituitary adenomas (NFPAs) primarily cause headaches, visual impairment and hypopituitarism due to the effect of the mass of the tumor. Surgery is the first-line treatment for these tumors. To date, no efficacious medical therapy exists for non-functioning adenomas. Previous studies have demonstrated that the Notch3 receptor is involved in the pathogenesis of various types of malignancies, including human NFPAs. The current study focused on the expression of the Notch3 receptor and its ligand Jagged1 in three types of pituitary adenomas and in the normal pituitary gland. Using quantitative real-time RT-PCR assays and western blot analyses, upregulated Notch3 and Jagged1 were observed in human NFPAs, but not in normal human pituitary glands or in hormone-secreting adenomas. Furthermore, Notch3 was positively correlated with Jagged1 at the mRNA and protein levels. These data indicate that Notch3 and Jagged1 may play an important role in the initiation and proliferation of human non-functioning adenomas, and there may be an interaction between Notch3 and Jagged1 in this process. Our study further elucidates the role of the Notch3 signaling pathway in the tumorigenesis of human NFPAs and provides a potential therapeutic target for the medical treatment of these tumors.

Management options for persistent postoperative acromegaly

This article presents management options for the patient with acromegaly after noncurative surgery. The current evidence for repeat surgery, adjuvant medical therapy with somatostatin analogues, dopamine agonists, the growth hormone receptor antagonist pegvisomant, combination medical therapy, and radiotherapy in the context of persistent postoperative disease are summarized. The relative advantages and disadvantages of each of these treatment modalities are explored, and a general treatment algorithm that integrates these modalities is proposed.

Cabergoline versus bromocriptine in the treatment of hyperprolactinemia: a systematic review of randomized controlled trials and meta-analysis

Cabergoline and bromocriptine are the most used drugs in the treatment of hyperprolactinemia, they are able to normalize the prolactin levels, restore gonadal function and promote tumor reduction in the majority of patients. We undertake a systematic review and meta-analysis of randomized controlled trials to compare cabergoline versus bromocriptine in the treatment of patients with idiopathic hyperprolactinemia and prolactinomas. The data sources were: Embase, Pubmed, Lilacs and Cochrane Central. The outcome measures were: normalization of prolactin secretion, restoration of gonadal function, reduction of tumoral volume, quality of life and adverse drug effects. Were identified 418 references and after screening by title and abstract, we obtained complete copies of 34 articles potentially eligible for inclusion in the review. From this total, 19 were selected to be included, but fifteen of them were excluded due to the following reasons: one randomized study compared cabergoline versus placebo and other randomized study compared different doses of cabergoline; five references were cases series; four were only controlled studies; three were retrospectives series and; one was a cohort study. Therefore, four publications were included in the review and in the final analysis. The meta-analysis of normalization of serum prolactin levels and menstruation with return of ovulatory cycle showed a significant difference in favor of cabergoline group (RR 0.67 [CI 95% 0.57, 0.80]) e (RR 0.74 [CI 95% 0.67, 0.83]), respectively. The number of adverse effects was significantly higher in the bromocriptine number than in cabergoline group (RR 1.43 [CI 95% 1.03, 1.98]). The meta-analysis showed new evidence favoring the use of cabergoline in comparison with bromocriptine for the treatment of prolactinomas and idiopathic hyperprolactinemia.

Reversal of endogenous dopamine receptor silencing in pituitary cells augments receptor-mediated apoptosis

Dopamine (DA)-agonist targeting of the DA D(2) receptor (D2R) in prolactinomas is the first-line treatment choice for suppression of prolactin and induction of tumor shrinkage. Resistance to DA agonists seems to be related to receptor number. Using the MMQ and GH3 pituitary cell lines, that either do or do not express D2R, respectively, we explored the epigenetic profile associated with the presence or absence of D2R in these cells lines. These studies led us to explore pharmacological strategies designed to restore receptor expression and thereby potentially augment DA agonist-mediated apoptosis. We show in GH3 cells that the D2R harbors increased CpG island-associated methylation and enrichment for histone H3K27me3. Conversely, MMQ cells and normal pituitaries show enrichment for H3K9Ac and barely detectable H3K27me3. Coculture of GH3 cells with the demethylating agent zebularine and the histone deacetylase inhibitor trichostatin A was responsible for a decrease in CpG island methylation and enrichment for the histone H3K9Ac mark. In addition, challenge of GH3 cells with zebularine alone or coculture with both agents led to expression of endogenous D2R in these cells. Induced expression D2R in GH3 cells was associated with a significant increase in apoptosis indices to challenge with either DA or bromocriptine. Specificity of a receptor-mediated response was established in coincubations with specific D2R antagonist and siRNA approaches in GH3 cell and D2R expressing MMQ cell lines. These studies point to the potential efficacy of combined treatment with epigenetic drugs and DA agonists for the medical management of different pituitary tumor subtypes, resistant to conventional therapies.

Dopamine agonist-resistant prolactinomas

The authors' object in this paper was to review the definition, epidemiology, biology, resistance mechanisms, and treatment options for dopamine agonist-resistant prolactinomas (DARPs). Prolactinomas are relatively unique among primary brain tumors in that medical treatment alone using dopamine agonists carries a high probability of disease control or even radiographic and endocrine remission, and thus has replaced surgery as the first line of therapy. Unfortunately, slightly less than 10% of patients with prolactinomas do not experience normalization of their prolactin levels in response to dopamine agonists, and harbor tumors that are resistant to dopamine agonist therapy. A literature review underscores that in male patients these DARPs are more likely to be invasive macroadenomas than dopamine agonist-responsive prolactinomas and that they are also more angiogenic, more proliferative, and more likely to exhibit cellular atypia. Estrogen receptor antagonists and temozolomide are the most commonly applied medical therapies in cases in which resection and radiosurgery have not induced remission of the hyperprolactinemia. Dopamine agonist-resistant prolactinomas exhibit aggressive behavior and tend to be large, invasive, hyperangiogenic tumors with high mitotic indices, which makes their management via surgery, radiosurgery, or alternative medical therapies challenging, thus underscoring the need for novel medical therapies or treatment regimens that target these lesions.

Pituitary somatostatin receptor signaling

Somatotropin-release inhibitory factor (SRIF) is a major regulator of pituitary function, mostly inhibiting hormone secretion and to a lesser extent pituitary cell growth. Five SRIF receptor subtypes (SSTR1-5) are ubiquitously expressed G-protein coupled receptors. In the pituitary, SSTR1, 2, 3 and 5 are expressed, with SSTR2 and SSTR5 predominating. As new SRIF analogs have recently been introduced for treatment of pituitary disease, we evaluate the current knowledge of cell-specific pituitary SRIF receptor signaling and highlight areas of future research for comprehensive understanding of these mechanisms. Elucidating pituitary SRIF receptor signaling enables understanding of pituitary hormone secretion and cell growth, and also encourages future therapeutic development for pituitary disorders.

Nonfunctioning pituitary adenomas: the Oxford experience

Nonfunctioning adenomas are the second most common type of pituitary tumor. Over the past few years, our knowledge of the epidemiology, natural history, diagnosis, treatment, and recurrence rates of these tumors has improved. Here, we highlight some of these advances and speculate on future avenues of research. In addition, we describe our own experience in the clinical management of patients with nonfunctioning adenomas. Serum prolactin levels are generally <2,000 mU/l in patients with these tumors; we propose that this level be used as the cut-off to differentiate nonfunctioning from prolactin-secreting adenomas. Despite increases in size in 19% of the microadenomas we studied, none of the patients who received no intervention developed visual complications. By contrast, 50% of untreated macroadenomas enlarged and 67% of affected patients experienced worsened or new visual-field defects. Although most recurrences develop in the first 5 years, recurrence has been reported up 14 years after surgery.

Estimated age- and sex-specific incidence and prevalence of dopamine agonist-treated hyperprolactinemia

CONTEXT

Few data exist on sex- and age-specific incidence and prevalence of idiopathic hyperprolactinemia and prolactinomas.

OBJECTIVES

Our objective was to assess incidence and prevalence of dopamine agonist-treated hyperprolactinemia by age and sex.

DESIGN

From the PHARMO network, we identified an open cohort of patients who were ever dispensed dopamine agonists for hyperprolactinemia. The network includes complete medication histories for more than 2 million community-dwelling residents. Prolonged use of low-dose dopamine agonist is a reliable marker for hyperprolactinemia, provided that use for Parkinson's disease and lactation withdrawal is excluded. Diagnoses were verified by prolactin values in a random subsample using the same network.

RESULTS

We identified 11,314 subjects with at least one dispensing of dopamine agonist in the period 1996-2006, of whom 1607 subjects were considered to have dopamine agonist-treated hyperprolactinemia based on the prescribing pattern. The majority of patients were women (n = 1342, 84%). The diagnosis proved to be incorrect in only 1.5% of a random subsample. The estimated incidence rate of dopamine agonist-treated hyperprolactinemia for women was 8.7/100,000 person-years and for men 1.4/100,000 person-years. The highest incidence rate was found in women 25-34 yr of age: 23.9/100,000 person-years. The mean prevalence of ever treated female patients was almost five times higher (93.9/100,000) compared with male patients (19.6/100,000).

CONCLUSION

The incidence rates and the prevalence of dopamine agonist-treated hyperprolactinemia showed an overall preponderance in women, with a strong peak for women aged 25-34 yr. In men, no peak was found.