Drug Insight: cabergoline and bromocriptine in the treatment of hyperprolactinemia in men and women

Invasive Pituitary Macroprolactinoma with Spontaneous CSF Rhinorrhea- A Case Report with a Review of the Literature and a Strategical Plan of Management

Cerebrospinal fluid (CSF) rhinorrhea is a rare and unexpected initial presentation of untreated invasive pituitary macroprolactinoma. This article aims to better understand the management of invasive pituitary macroprolactinoma, especially in cases where the patient initially presents with a CSF leak. We describe a case of a 36-year-old male with untreated invasive macroprolactinoma with a CSF leak at the initial presentation. The role and timing of medical and surgical treatment in such a setting are outlined in detail. Medical therapy has shown both worsening and resolution of the CSF leak. We propose a ''Sandwich Therapy'' in Dopamine agonist (DA) responsive cases where the leak persists, which includes initial DA therapy, followed by endoscopic Transsphenoidal surgery (TSS) with DA therapy and then followed by the post-operative continuation of DA therapy.

A comprehensive review of the new FIGO classification of ovulatory disorders

BACKGROUND

The World Health Organization (WHO) system for the classification of disorders of ovulation was produced 50 years ago and, by international consensus, has been updated by the International Federation of Gynecology and Obstetrics (FIGO).

OBJECTIVE AND RATIONALE

This review outlines in detail each component of the FIGO HyPO-P (hypothalamic, pituitary, ovarian, PCOS) classification with a concise description of each cause, and thereby provides a systematic method for diagnosis and management.

SEARCH METHODS

We searched the published articles in the PubMed database in the English-language literature until October 2022, containing the keywords ovulatory disorders; ovulatory dysfunction; anovulation, and each subheading in the FIGO HyPO-P classification. We did not include abstracts or conference proceedings because the data are usually difficult to assess.

OUTCOMES

We present the most comprehensive review of all disorders of ovulation, published systematically according to the logical FIGO classification.

WIDER IMPLICATIONS

Improving the diagnosis of an individual's ovulatory dysfunction will significantly impact clinical practice by enabling healthcare practitioners to make a precise diagnosis and plan appropriate management.

Characterization of Leptin Secretion in Premenopausal Obese Women Treated with Bromocriptine

Leptin, a hormone secreted by adipose tissue, is primarily responsible for inhibiting hunger and maintaining energy balance. Improper leptin secretion may result in hyperleptinemia (excess secretion of leptin) or leptin resistance, both of which contribute to obesity. Diagnosing abnormal leptin secretion may help treat this underlying cause of obesity. Therefore, continuous monitoring of the level of leptin may help characterize its secretion dynamics and also help devise an appropriate treatment. In this research, we consider leptin hormone concentration data taken over a 24 hour time period from eighteen healthy premenopausal obese women before and after treatment with a dopamine agonist, bromocriptine, and deconvolve the observed leptin hormone levels to estimate the number, timing, and magnitude of the underlying leptin secretory pulses. We find that there is an overall decrease in leptin secretion, particularly during sleep, but the changes in the secretory and clearance rates, and the number of pulses underlying the secretion process are not statistically significant.Clinical relevance- This work seeks to understand the effect of bromocriptine on leptin secretory dynamics and will help further current understanding of the effect of bromocriptine in relation to obesity.

Multi-omics integration analysis of GPCRs in pan-cancer to uncover inter-omics relationships and potential driver genes

G protein-coupled receptors (GPCRs) are the largest drug target family. Unfortunately, applications of GPCRs in cancer therapy are scarce due to very limited knowledge regarding their correlations with cancers. Multi-omics data enables systematic investigations of GPCRs, yet their effective integration remains a challenge due to the complexity of the data. Here, we adopt two types of integration strategies, multi-staged and meta-dimensional approaches, to fully characterize somatic mutations, somatic copy number alterations (SCNAs), DNA methylations, and mRNA expressions of GPCRs in 33 cancers. Results from the multi-staged integration reveal that GPCR mutations cannot well predict expression dysregulation. The correlations between expressions and SCNAs are primarily positive, while correlations of the methylations with expressions and SCNAs are bimodal with negative correlations predominating. Based on these correlations, 32 and 144 potential cancer-related GPCRs driven by aberrant SCNA and methylation are identified, respectively. In addition, the meta-dimensional integration analysis is carried out by using deep learning models, which predict more than one hundred GPCRs as potential oncogenes. When comparing results between the two integration strategies, 165 cancer-related GPCRs are common in both, suggesting that they should be prioritized in future studies. However, 172 GPCRs emerge in only one, indicating that the two integration strategies should be considered concurrently to complement the information missed by the other such that obtain a more comprehensive understanding. Finally, correlation analysis further reveals that GPCRs, in particular for the class A and adhesion receptors, are generally immune-related. In a whole, the work is for the first time to reveal the associations between different omics layers and highlight the necessity of combing the two strategies in identifying cancer-related GPCRs.

Impaired Cardiometabolic Effects of Bromocriptine in Men With Early-Onset Androgenic Alopecia

Both hyperprolactinemia and early-onset androgenic alopecia are associated with increased cardiometabolic risk. The aim of this study was to assess whether early-onset male-pattern baldness modifies cardiometabolic effects of bromocriptine in men with prolactin excess. The study included 2 groups of men with prolactin excess: individuals with early-onset androgenic alopecia (group 1) and individuals with normal hair growth (group 2). Both groups were matched for age, smoking habits, body mass index, blood pressure, and prolactin levels. Over the entire study period (4 months), all participants were treated with bromocriptine (7.5 mg daily). Plasma levels of hormones (prolactin, total testosterone, and bioavailable testosterone), glucose homeostasis markers, lipids, uric acid, high-sensitivity C-reactive protein (hsCRP), fibrinogen, homocysteine, and the urinary albumin-to-creatinine ratio (UACR) were measured at the beginning and at the end of the study period. The two groups differed in total testosterone, bioavailable testosterone, insulin sensitivity, high-density lipoprotein (HDL) cholesterol, triglycerides, uric acid, hsCRP, fibrinogen, homocysteine, and UACR. In both groups, bromocriptine reduced prolactin, increased total and bioavailable testosterone, improved insulin sensitivity, and decreased uric acid, hsCRP, and homocysteine. The impact on prolactin, insulin sensitivity, uric acid, hsCRP, and homocysteine was stronger in group 2 than in group 1. Only in group 2 did the drug increase HDL cholesterol and decrease triglycerides, fibrinogen, and UACR. The impact on cardiometabolic risk factors correlated with a reduction in prolactin levels and an improvement in insulin sensitivity, and, in group 1, inversely correlated with testosterone levels. The obtained results suggest that men with early-onset androgenic alopecia are partially resistant to the cardiometabolic effects of bromocriptine.

11C-methionine PET aids localization of microprolactinomas in patients with intolerance or resistance to dopamine agonist therapy

PURPOSE

To assess the potential for ¹¹C-methionine PET (Met-PET) coregistered with volumetric magnetic resonance imaging (Met-PET/MR^CR) to inform clinical decision making in patients with poorly visualized or occult microprolactinomas and dopamine agonist intolerance or resistance.

PATIENTS AND METHODS

Thirteen patients with pituitary microprolactinomas, and who were intolerant (n = 11) or resistant (n = 2) to dopamine agonist therapy, were referred to our specialist pituitary centre for Met-PET/MR^CR between 2016 and 2020. All patients had persistent hyperprolactinemia and were being considered for surgical intervention, but standard clinical MRI had shown either no visible adenoma or equivocal appearances.

RESULTS

In all 13 patients Met-PET/MR^CR demonstrated a single focus of avid tracer uptake. This was localized either to the right or left side of the sella in 12 subjects. In one patient, who had previously undergone surgery for a left-sided adenoma, recurrent tumor was unexpectedly identified in the left cavernous sinus. Five patients underwent endoscopic transsphenoidal selective adenomectomy, with subsequent complete remission of hyperprolactinaemia and normalization of other pituitary function; three patients are awaiting surgery. In the patient with inoperable cavernous sinus disease PET-guided stereotactic radiosurgery (SRS) was performed with subsequent near-normalization of serum prolactin. Two patients elected for a further trial of medical therapy, while two declined surgery or radiotherapy and chose to remain off medical treatment.

CONCLUSIONS

In patients with dopamine agonist intolerance or resistance, and indeterminate pituitary MRI, molecular (functional) imaging with Met-PET/MR^CR can allow precise localization of a microprolactinoma to facilitate selective surgical adenomectomy or SRS.

Therapeutic potential of dopamine agonists in the treatment of type 2 diabetes mellitus

Diabetes is a global health concern that has affected almost 415 million people globally. Bromocriptine is a dopamine D2 agonist, which is a Food and Drug Administration (FDA)-approved drug to treat type 2 diabetes mellitus (T2DM) patients. However, it is considered that a novel treatment therapy is required which can be used in the treatment of diabetes with or without other antidiabetic agents. Dopamine agonists are usually used in neurological disorders like Parkinson's disease (PD), restless leg syndrome, and hyperprolactinemia. However, dopamine agonists including bromocriptine and cabergoline are also effective in reducing the glycemic level in T2DM patients. Bromocriptine was formerly used for the treatment of PD, hyperprolactinemia, and restless leg syndrome, but now it is used for improving glycemic levels as well as reducing free fatty acids and triglycerides. In addition, cabergoline has been found to be effective in glycemic control, but this drug is yet to be approved by the FDA due to its limitations and lack of study. Findings of the clinical trials of bromocriptine have suggested that it reduces almost 0.4-0.8% glycated hemoglobin and cardiovascular risk by 40% in insulin-resistant patients. Moreover, the safe use of bromocriptine in obese T2DM patients makes it a more attractive option as it causes weight loss. Indeed, bromocriptine is a novel therapy for T2DM patients, as its mechanism of action is unique in T2DM patients with minimal adverse effects. This review summarizes the potential of dopamine agonists in the treatment of T2DM.

Current and Emerging Medical Therapies in Pituitary Tumors

Pituitary tumors (PT) represent in, the majority of cases, benign tumors for which surgical treatment still remains, except for prolactin-secreting PT, the first-line therapeutic option. Nonetheless, the role played by medical therapies for the management of such tumors, before or after surgery, has evolved considerably, due in part to the recent development of well-tolerated and highly efficient molecules. In this review, our aim was to present a state-of-the-art of the current medical therapies used in the field of PT and the benefits and caveats for each of them, and further specify their positioning in the therapeutic algorithm of each phenotype. Finally, we discuss the future of PT medical therapies, based on the most recent studies published in this field.

Efficacy and Cerebrospinal Fluid Rhinorrhea after Cabergoline Treatment in Patients with Bioactive Macroprolactinoma

Predicting dopamine agonist resistance in patients with macroprolactinoma is essential for clinicians to prevent treatment failure and subsequent complications such as medication-induced cerebrospinal fluid (CSF) rhinorrhea. We evaluated the features of patients with cabergoline resistance and CSF rhinorrhea in patients with prolactinomas with prolactin levels ≥1000 ng/mL. A total of 140 patients who were newly diagnosed with prolactinoma secreting only prolactin ≥1000 ng/mL and treated with cabergoline for the first time were included in this study. Based on the hormonal and radiologic response of the prolactinoma, the patients were divided into responders and non-responders. Non-responders (36/140, 25.8%) included a higher number of patients receiving hormone replacement than responders (responders, n (%) = 12(11.5) vs. non-responders = 13(36.1), p = 0.001). In propensity score matching analysis, patients who developed CSF rhinorrhea presented more frequent hormone deficiency than responders regardless of initial cabergoline dose. Hormone deficiency was associated with a greater odds ratio for the risk of non-responders (adjusted odds ratio = 5.13, 95% CI 1.96-13.46, p = 0.001). Cabergoline was effective in bioactive macroprolactinoma. Furthermore, initial cabergoline dose was not significantly associated with long-term responsiveness and development of CSF rhinorrhea but the hypopituitarism was independently associated with an increased risk of cabergoline resistance and CSF rhinorrhea.

Healthcare utilization and costs among prolactinoma patients: a cross-sectional study and analysis of determinants

PURPOSE

Prolactinomas are the most prevalent functioning pituitary adenomas. They affect gonadal function as well as health-related quality of life (HRQoL). This study aimed to report healthcare utilization and costs, including their determinants, for prolactinoma patients.

METHODS

Cross-sectional study of 116 adult prolactinoma patients in chronic care in a Dutch tertiary referral center. Patients completed four validated questionnaires, assessing healthcare utilization and costs over the previous 12 months (Medical Consumption Questionnaire), disease bother and needs (Leiden Bother and Needs Questionnaire Pituitary), HRQoL (Short Form-36), and self-reported health status (EuroQol 5D). Regression analyses were used to assess associations between disease-related characteristics and healthcare utilization and costs.

RESULTS

Mean age was 52.0 years (SD 13.7) and median follow-up was 15.0 years (IQR 7.6-26.1). Patients visited the endocrinologist (86.2%), general practitioner (37.9%), and ophthalmologist (25.0%) most frequently. Psychological care was used by 12.9% of patients and 5% were admitted to hospital. Mean annual healthcare costs were €1928 (SD 3319), mainly for pituitary-specific medication (37.6% of total costs), hospitalization (19.4%) and specialist care (16.1%). Determinants for higher healthcare utilization and costs were greater disease bother and needs for support, lower HRQoL, elevated prolactin, and longer disease duration, while tumor size, hypopituitarism and adrenal insufficiency were not significantly associated with healthcare utilization and costs.

CONCLUSION

Healthcare utilization and costs of prolactinoma patients are related to patient-reported HRQoL, bother by disease and needs for support. Therefore, addressing patients' HRQoL and needs is a way forward to improve efficiency of care and patients' health status.

Cabergoline in Treatment of Methamphetamine-Dependent Patients and Its Effect on Serum Level of Glial Cell-Derived Neurotrophic Factor: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

BACKGROUND

Methamphetamine use disorder is an important public health problem, especially in the younger generation, and associated with various psychiatric, cognitive, social, economic, and legal issues. Cabergoline, a drug with dopaminergic properties and long half-life, has been considered for the treatment of stimulant dependence. The systemic use of cabergoline has been shown to increase glial cell-derived neurotrophic factor (GDNF) expression.

OBJECTIVE

In this study, we investigated the effects of cabergoline on the serum level of GDNF and its effect on abstaining from methamphetamine in individuals treated for methamphetamine use disorder.

METHOD

Sixty male subjects with methamphetamine use disorder were randomly assigned to 2 groups receiving cabergoline and placebo, respectively. During a 12-week follow-up, we compared the serum level of GDNF, urine test results for methamphetamine use, and depression scale between the 2 groups.

RESULTS

We found that serum GDNF was lower in subjects who used methamphetamine than healthy subjects (p < 0.0001). However, the serum level of GDNF was not associated with cabergoline use. The rising number of cases testing positive in the placebo group showed a trend resulting in no significant difference between cases testing positive and negative (p = 0.585) at the end of week 12. In the verum group, however, the significantly high number of cases who tested negative - sober - for substances observed in early stages (weeks 7-8) continued to remain significantly higher till the end of the study (p = 0.043), resembling an association between treatment with cabergoline and remaining sober. Although reduced during treatment, recovery from depression was not associated with cabergoline treatment.

CONCLUSION

The findings of this study confirmed the effect of cabergoline in reducing methamphetamine use. However, a serum level of the GDNF increase, as seen in animal studies, was not associated with cabergoline treatment of human subjects. This study was registered at the Iranian Registry of Clinical Trials (TRN:IRCT2015050422077N1, October 06, 2015, https://en.irct.ir/trial/19134).

Hyperprolactinaemia

Hyperprolactinaemia is one of the most common problems in clinical endocrinology. It relates with various aetiologies (physiological, pharmacological, pathological), the clarification of which requires careful history taking and clinical assessment. Analytical issues (presence of macroprolactin or of the hook effect) need to be taken into account when interpreting the prolactin values. Medications and sellar/parasellar masses (prolactin secreting or acting through “stalk effect”) are the most common causes of pathological hyperprolactinaemia. Hypogonadism and galactorrhoea are well-recognized manifestations of prolactin excess, although its implications on bone health, metabolism and immune system are also expanding. Treatment mainly aims at restoration and maintenance of normal gonadal function/fertility, and prevention of osteoporosis; further specific management strategies depend on the underlying cause. In this review, we provide an update on the diagnostic and management approaches for the patient with hyperprolactinaemia and on the current data looking at the impact of high prolactin on metabolism, cardiovascular and immune systems.

Tumor suppressor miR-145-5p sensitizes prolactinoma to bromocriptine by downregulating TPT1

PURPOSE

Prolactinoma is the most commonly seen secretory tumor of pituitary glands, which accounts for approximately up to 40% of total pituitary adenomas. Due to its high drug resistance, dopamine agonist, such as bromocriptine, has limited effect on the treatment of patients with prolactinoma. Recent discoveries have revealed that multiple miRNAs were involved in regulating drug resistance. In this research, we explored the relationship between miR-145-5p expression as well as bromocriptine sensitivity both in vitro and in vivo.

METHODS

To study the role of miR-145-5p in drug resistance of prolactinoma, the expression levels of miR-145-5p in bromocriptine-resistant prolactinoma cell line MMQ/BRC and its parental cell line MMQ cells, 24 bromocriptine-resistant as well as eight sensitive clinical samples were measured by qRT-PCR. Moreover, CCK8, flow cytometry and immunofluorescence were performed to identify the biological characteristics of MMQ/BRC and MMQ. TPT1 was predicted as a direct target gene of miR-145-5p by bioinformatic methods. In addition, qRT-PCR, western blot and immunohistochemistry were used to detect the expression level of TPT1 in clinical specimens and cell lines. Xenograft mouse model was constructed to analyze whether miR-145-5p could reverse bromocriptine resistance in prolactinoma in vivo.

RESULTS

In our study, bromocriptine-resistant prolactinoma clinical samples and cell line had decreased miR-145-5p levels and expressed high levels of TPT1 compared with their sensitive counterparts. Bioinformatic methods and our preliminary dual luciferase reporter assay were utilized to elucidate that TPT1 was a direct target gene of miR-145-5p. Furthermore, introducing miR-145-5p mimic into MMQ cells led to a decrease of IC50 along with upregulation of TPT1; nevertheless, transfecting the corresponding inhibitor into MMQ cells resulted in an upregulation of IC50 as well as reduction of TPT1.

CONCLUSIONS

Collectively, our findings elucidated the role of miR-145-5p as an important regulator of drug resistance in prolactinoma by controlling TPT1, and implicated the potential application of miR-145-5p in cancer therapy as well.

Beyond tribulus (Tribulus terrestris L.): The effects of phytotherapics on testosterone, sperm and prostate parameters

ETHNO-PHARMACOLOGICAL RELEVANCE

Phytotherapeutic approaches have been widely proposed to improve male health. Despite the well-touted effects of tribulus (Tribulus terrestris L) on men's health, an optimal phytotherapy remains an elusive challenge.

AIM OF THE REVIEW

We sought to critically analyze the evidence in the phytotherapic literature beyond the effects of tribulus on testosterone (T) concentration and sperm analysis to also include indications for prostate health.

MATERIALS AND METHODS

A focused literature search was conducted to include studies published in Cochrane, Pubmed, and Web of Science databases between the years 2002 and 2018.

RESULTS

The use of tribulus and maca (Lepidium meyenii Walp, Brassicaceae) were not scientifically supported to improve serum T levels in men. Moderate evidence supports the use of long Jack (Eurycoma longifolia Jack, Simaroubaceae), mucuna (Mucuna pruriens (L.) DC., Fabaceae), ashwagandha (Withania somnifera (L.) Dunal, Solanaceae), fenugreek (Trigonella foenum-graceum L., Fabaceae), and black seeds (Nigella sativa L., Ranunculaceae) to increase total T and improve seminal parameters. Data suggests an increase in total T with the use of 5000 mg/d of powdered mucuna seed and ashwagandha root (151 and 143 ng/dL, respectively) over a 12-week period in patients with oligozoospermia. The use of mucuna was supported for patients with oligozoospermia to improve sperm parameters, with an increase of 83.3 million/mL observed after use of 5000 mg/d of powdered mucuna seed over a 12-week period. Evidence supporting the use of saw palmetto (Serenoa repens, (W.Bartram) Small, Arecaceae) to improve prostate health remains equivocal; whereas, evidence supporting the use of Pygeum africanum Hook.f., Rosaceae, Urtica dioica L., Urticaceae, beta-sitosterols, pollen extract, onion, garlic, and tomato, appears favorable and promising.

CONCLUSION

Scientific evidence supports the use of mucuna and ashwagandha as phytotherapics for improving serum T concentrations and semen parameters. Despite inconclusive evidence for use of tribulus as a T booster, it may provide advantageous effects on sperm parameters in men with idiopathic infertility. Nutraceutical strategies and some phytotherapics may also be effective to promote prostate health. Popular foodstuffs (onion, garlic, and tomato), nutraceutical agents (pollen extract and beta-sitosterols), and herbal medicines (Pygeum africanum and Urtica dioica) are rational approaches.

Clinical management of difficult to treat macroprolactinomas

INTRODUCTION

Prolactinomas represent the most common pituitary adenomas encountered in the clinic. While a majority of these tumors will be successfully treated by dopamine agonist (DA) such as cabergoline, their management becomes problematic since a resistance to DA can occur and/or if the tumor displays features of aggressiveness, two conditions that are closely related.

AREAS COVERED

Epidemiology and medical treatment of prolactinomas; resistance to DA and molecular basis of DA-resistance; therapeutical alternatives in case of DA-resistant Prolactinomas and therapies in development; summarizing conclusions.

EXPERT OPINION

The management of DA-resistant prolactinomas requires a multidisciplinary approach by an expert team. Along with discussions about surgery with or without gamma knife radiosurgery, genetic screening for multiple endocrine neoplasia type 1 (MEN1) syndrome is actively discussed in a case-by-case approach. In case of surgery, a careful analysis of the tumor sample can provide information about its aggressivity potential according to recent criteria. Ultimately, temozolomide can be indicated if the tumor is rapidly growing and/or threatening for the patient.

Cabergoline for the treatment of bromocriptine-resistant invasive giant prolactinomas

PURPOSE

Few studies have specifically focused on the effect of cabergoline on invasive giant prolactinomas (IGPs) resistant to bromocriptine. This study aims to evaluate whether cabergoline could be used as an effective therapy for patients with bromocriptine-resistant IGPs.

METHODS

This retrospective study included 15 patients with bromocriptine-resistant IGPs who received treatment at our department during 2007-2015. Cabergoline was administered in all 15 patients, with the dose adjusted depending on the prolactin response of each patient. Parameters for outcome assessment included prolactin level, pituitary function, tumor size, improvement of the clinical symptoms, visual field defects, drug tolerance, and disease recurrence.

RESULTS

Cabergoline was effective for the treatment of the patients with bromocriptine -resistant IGPs as represented by normalization of the prolactin level in 12/15 patients; improvement or normalization of the pituitary function in 4/5 patients with hypopituitarism; significant reduction in tumor size in 14/15 patients; and relief of the clinical symptoms in 11/15 patients. All 15 patients showed good tolerance to cabergoline. In addition, no recurrence was observed during the mean follow-up period of 63.47 (range 30-145) months.

CONCLUSIONS

Data of this retrospective study demonstrate that cabergoline is an excellent option for the treatment of patients with bromocriptine-resistant IGPs.

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.

Optimal timing of dopamine agonist withdrawal in patients with hyperprolactinemia: a systematic review and meta-analysis

PURPOSE

Dopamine agonists (DAs) are recommended as first-line treatment for patients with hyperprolactinemia. Generally, it is accepted that patients with hyperprolactinemia do not need lifelong medication, but the optimal timing for DA withdrawal has not been determined. The aim of this systematic review and meta-analysis is to assess the impact of DA withdrawal on the clinical outcomes of patients with hyperprolactinemia, and to explore possible factors affecting successful DA withdrawal.

METHODS

The databases of PubMed, Cochrane and EMBASE were searched up to May 2016.

RESULTS

The proportion of patients with persisting normoprolactinemia after DA withdrawal reached 36.6% in a random effects model (95% CI, 29.4-44.2%; I-squared: 82.5%). Data of stratified analysis showed that the success rate of drug withdrawal was high in patients using cabergoline (CAB) as the only treatment (41.2%; 95% CI 32.3-50.4%) and those using CAB over 24 months (48.7%; 95% CI 38.9-58.5%), especially in patients with idiopathic hyperprolactinemia (73.2%; 95% CI 55.6-87.7%). In addition, patients who received a low maintenance dose of CAB, and had a significant reduction in tumor size (over 50%) before withdrawal, were more likely to achieve success (51.5 and 49.4%, respectively).

CONCLUSION

The success rate of DA withdrawal has increased in recent years. Further, the success rate of CAB withdrawal was higher than that of bromocriptine, especially in patients with a duration of treatment longer than 24 months. Conclusively, the probability of success was higher in patients who received low-dose CAB maintenance treatment and those who achieved a significant reduction in tumor size before withdrawal.

The Chance of Permanent Cure for Micro- and Macroprolactinomas, Medication or Surgery? A Systematic Review and Meta-Analysis

Background: This meta-analysis aims to evaluate the long-term efficacy of medication treatment vs. surgery treatment in patients with prolactinomas. Methods: An electronic literature search was performed using MEDLINE, EMBASE and Web of Science databases for studies dated before July in 2018. Patients with prolactinomas received primary dopamine agonists (DAs) treatment or primary surgical interventions were included in this study. A systematic review and meta-analysis were performed in pertinent studies meeting eligible criteria. The clinical outcome was measured by the long-term remission rate of prolactin (PRL) in each cohort. The pooled data was analyzed according to a random effect model. Results: Thirteen publications with total 809 patients were included in the final meta-analysis. In the overall patients with prolactinomas, long-term remission rate was achieved in 88% patients treated with surgeries and in 52% patients treated with DAs (P = 0.001). The long-term remission rates in surgery cohort were also significantly higher than medication cohort in both microprolactinomas and macroprolactinomas (91 vs. 60%, P = 0.002; 77 vs. 43%, P = 0.003). Conclusions: Patients with prolactinomas, especially microprolactinomas, can consider transsphenoidal surgery as an alternative first-line treatment strategy. After receiving primary surgical intervention, administration of DAs should be considered based on the postoperative PRL level to achieve the best long-term remission rate.

Time Course of Resolution of Hyperprolactinemia After Transsphenoidal Surgery Among Patients Presenting with Pituitary Stalk Compression

BACKGROUND

Primary lactotroph disinhibition, or stalk effect, occurs when mechanical compression of the pituitary stalk disrupts the tonic inhibition by dopamine released by the hypothalamus. The resolution of pituitary stalk effect-related hyperprolactinemia postoperatively has not been studied in a large cohort of patients. We performed a retrospective review to investigate the time course of recovery of lactotroph disinhibition after transsphenoidal surgery.

METHODS

Medical records were retrospectively reviewed for all patients undergoing transsphenoidal surgery with the senior author from April 2008 to November 2014.

RESULTS

Of 556 pituitary adenomas, 289 (52.0%) were eliminated: 77 (13.9%) had an immunohistochemically confirmed prolactinoma, 119 (21.4%) patients had previous surgery, 93 (16.7%) had incomplete medical records, leaving 267 patients (48.0%) for final analysis. Of these patients, 72 (27.0%) had increased serum prolactin levels (≥23.3 ng/mL), suggestive of pituitary stalk effect (maximum prolactin level = 148.0 ng/mL). Patients with stalk effect were more likely than those with normal serum prolactin levels to present with menstrual dysfunction (29.7% vs. 19.4%; P < 0.01) and galactorrhea (11.1% vs. 2.1%; P < 0.01). Patients with lactotroph disinhibition were more likely to harbor macroadenomas than were patients who did not show lactotroph disinhibition (81.9% vs. 70.2%; P = 0.06). Among patients with increased preoperative prolactin, 77.8% experienced normalization of serum prolactin postoperatively, galactorrhea improved in 100%, sexual dysfunction resolved in 66.6%, and menstrual dysfunction among premenopausal females normalized in 73.3% at last follow-up (mean, 5.35 years; range, 0.1-10 years).

CONCLUSIONS

Transsphenoidal surgery can provide durable normalization of serum prolactin levels and related symptoms caused by pituitary stalk compression-related lactotroph disinhibition.

Inhibition of SKP2 Sensitizes Bromocriptine-Induced Apoptosis in Human Prolactinoma Cells

PURPOSE

Prolactinoma (prolactin-secreting pituitary adenoma) is one of the most common estrogen-related functional pituitary tumors. As an agonist of the dopamine D2 receptor, bromocriptine is used widely to inhibit prolactinoma progression. On the other hand, it is not always effective in clinical application. Although a dopamine D2 receptor deficiency contributes to the impaired efficiency of bromocriptine therapy to some extent, it is unknown whether there some other underlying mechanisms leading to bromocriptine resistance in prolactinoma treatment. That is the main point addressed in this project.

MATERIALS AND METHODS

Human prolactinoma samples were used to analyze the S-phase kinase associated protein 2 (SKP2) expression level. Nutlin-3/adriamycin/cisplatin-treated GH3 and MMQ cells were used to analyze apoptosis in SKP2 overexpression or knockdown cells. SKP2 expression and the interaction partners of SKP2 were also detected after a bromocriptine treatment in 293T. Apoptosis was analyzed in C25 and bromocriptine-treated GH3 cells.

RESULTS

Compared to normal pituitary samples, most prolactinoma samples exhibit higher levels of SKP2 expression, which could inhibit apoptosis in a p53-dependent manner. In addition, the bromocriptine treatment prolonged the half-life of SKP2 and resulted in SKP2 overexpression to a greater extent, which in turn compromised its pro-apoptotic effect. As a result, the bromocriptine treatment combined with C25 (a SKP2 inhibitor) led to the maximal apoptosis of human prolactinoma cells.

CONCLUSION

These findings indicated that SKP2 inhibition sensitized the prolactinoma cells to bromocriptine and helped promote apoptosis. Moreover, a combined treatment of bromocriptine and C25 may contribute to the maximal apoptosis of human prolactinoma cells.

Male prolactinomas presenting with normal testosterone levels

In men harboring prolactinoma the most common symptoms are related to hypogonadism, including decreased libido, erectile dysfunction, and gynecomastia. These men characteristically present with elevated serum prolactin (PRL) levels, suppressed gonadotropins, and low testosterone levels. We studied a group of 11 unique men with prolactinomas presenting with testosterone levels within the normal range (≥2.6 ng/ml; cohort A), and compared them to 11 prolactinoma men with borderline baseline testosterone (2.1-2.5 ng/ml; cohort B) and to a cohort of 34 prolactinoma patients with low testosterone levels (≤2 ng/ml; cohort C). Mean testosterone levels at presentation were 3.91 ± 0.9 ng/ml in cohort A (range, 2.6-5.2 ng/ml), 2.44 ± 0.16 ng/ml in cohort B and 0.96 ± 0.6 in cohort C (p < 0.001). Mean baseline PRL levels were >20 times above normal in cohort A compared to >100 times above normal in cohorts B and C. Symptoms of hypogonadism were present in 55, 64 and 76% of men in groups A, B and C, respectively. There was a trend towards a larger tumor size in the low testosterone group (p = 0.06). Visual fields defects at presentation were more prevalent in this cohort (C). With cabergoline, testosterone level increased from 3.91 to 6.42 ng/ml (Δ = 2.51 ng/ml) in cohort A, from 2.44 to 5.63 ng/ml (Δ = 3.19 ng/ml) in cohort B, and from 0.96 to 3.30 ng/ml (Δ = 2.34 ng/ml) in cohort C (p < 0.05 for each group). Symptoms of hypogonadism improved following treatment in 83% of symptomatic men in cohort A. Normal testosterone does not exclude the likelihood of prolactinoma in men. When treated with cabergoline, testosterone levels in these men can increase higher within the normal range together with clinical improvement.

Recent advances in the discovery and preclinical testing of novel compounds for the prevention and/or treatment of alcohol use disorders

Alcohol abuse and dependence have a staggering socioeconomic impact, yet current therapeutic strategies are largely inadequate to treat these disorders. Thus, the development of new strategies that can effectively prevent alcohol use disorders (AUDs) is of paramount importance. Currently approved medications attempt to deter alcohol intake by blocking ethanol metabolism or by targeting the neurochemical systems downstream of the cascades leading to craving and dependence. Unfortunately, these medications have provided only limited success as indicated by the continued high rates of alcohol abuse and alcoholism. The lack of currently available effective treatment strategies is highlighted by the urgent call by the NIAAA to find new and paradigm-changing therapeutics to either prevent or treat alcohol-related problems. This mini-review highlights recent findings from 4 laboratories with a focus on compounds that have the potential to be novel therapeutic agents that can be developed for the prevention and/or treatment of AUDs.

Extralabel use of cabergoline in the treatment of a pituitary adenoma in a rat

CASE DESCRIPTION

A 0.65-kg (1.43-lb) 24-month-old sexually intact male albino pet rat was examined because of a 3-week history of hypodipsia, apparent blindness, and sudden change in behavior.

CLINICAL FINDINGS

The rat was able to move around its cage but appeared unaware of its surroundings, was visually unresponsive, and seemed unusually aggressive. The rat's hind limbs appeared mildly paretic, and it had sporadic difficulty placing its hind limbs on a flat surface. Given the rat's age, history, and physical examination findings, the primary differential diagnosis was a pituitary tumor. Magnetic resonance imaging (MRI) of the rat's brain was performed and revealed a large pituitary mass, which was indicative of a tumor.

TREATMENT AND OUTCOME

Cabergoline (0.6 mg/kg [0.27 mg/lb], PO, q 72 h) was administered. On follow-up MRI 2 months later, the pituitary mass had substantially decreased in size. For 6 months following the second MRI study, the rat continued to receive the same dosage of cabergoline and had no clinical signs of disease or unusual behavior. However, at 8.5 months after the start of the treatment, the rat was in poor condition and had clinical signs similar to those initially. A third MRI study was performed and revealed substantial regrowth of the mass. The rat was euthanized and a necropsy was performed; a histopathologic diagnosis of pituitary adenoma was made.

CLINICAL RELEVANCE

Pituitary adenomas have long been recognized as a common finding in geriatric rats (> 18 months old). Affected rats may respond favorably to oral administration of cabergoline.

Endogenous prolactin generated during peripheral inflammation contributes to thermal hyperalgesia

Prolactin (PRL) is a hormone and a neuromodulator. It sensitizes TRPV1 (transient receptor potential cation channel subfamily V member 1) responses in sensory neurons, but it is not clear whether peripheral inflammation results in the release of endogenous PRL, or whether endogenous PRL is capable of acting as an inflammatory mediator in a sex-dependent manner. To address these questions, we examined inflammation-induced release of endogenous PRL, and its regulation of thermal hyperalgesia in female and male rats. PRL is expressed in several types of peripheral neuronal and non-neuronal cells, including TRPV1-positive nerve fibers, preadipocytes and activated macrophages/monocytes localized in the vicinity of nerves. Evaluation of PRL levels in hindpaws and plasma indicated that complete Freund's adjuvant (CFA) stimulates release of peripheral, but not systemic, PRL within 6-48 h in both ovariectomized females with estradiol replacement (OVX-E) and intact male rats. The time course of release varies in OVX-E and intact male rats. We next employed the prolactin receptor (PRL-R) antagonist Δ1-9-G129R-hPRL to assess the role of locally produced PRL in nociception. Applied at a ratio of 1 : 1 (PRL:Δ1-9-G129R-hPRL; 40 nm each), this antagonist was able to nearly (≈ 80%) reverse PRL-induced sensitization of capsaicin responses in rat sensory neurons. CFA-induced inflammatory thermal hyperalgesia in OVX-E rat hindpaws was significantly reduced in a dose-dependent manner by the PRL-R antagonist at 6 h but not at 24 h. In contrast, PRL contributed to inflammatory thermal hyperalgesia in intact male rats at 24, but not at 6 h. These findings indicate that inflammation leads to accumulation of endogenous PRL in female and male rats. Furthermore, PRL acts as an inflammatory mediator at different time points for female and intact male rats.

Effect of dopaminergic drug treatment on surgical findings in prolactinomas

It has been reported that prolactinomas treated with Bromocriptine (BROM) show fibrosis that may interfere with complete surgical resection. The same has not been reported for Cabergoline (CAB). We retrospectively studied 24 consecutive patients (13 females, mean age 40 years, range 16-60) with histopathologically confirmed prolactinomas undergoing surgical resection at Johns Hopkins Hospital between 1992 and 2009. We compared these prolactinomas to 34 patients (22 females, mean age 42.9 years, range 15-75) with GH-secreting adenoma. The operative notes from 7 different neurosurgeons were reviewed to catalog the tumors as fibrous or not fibrous. Of the 24 prolactinomas, 21 (87.5%) were previously treated with DA. Indication for surgery was: DA resistance (n.5), DA intolerance (n.6), persistent mass effect (n.7) and CSF leak (n.3). Five (14.7%) of GH-secreting adenomas, were exposed to DA and/or somatostatin analogs. We found that 54% of prolactinomas and only 6% of GH-secreting adenomas were described as fibrous. 10/12 (77%) of prolactinomas exposed to BROM for at least 1 month, 2/9 (22%) exposed to CAB only, and 1/3 (33%) not previously treated were fibrous (P < 0.05). The mean BROM cumulative dose was 406 mg (range 75-1,375), while CAB dose was 28 mg (range 6-70). Only 18% of non-fibrous prolactinomas had been exposed to BROM. Only 3 patients had persistent biochemical remission (2 treated with CAB and 1 not treated). Patients exposed to BROM for at least 1 month are more likely to have tumor fibrosis than patients that are untreated or treated with CAB.

The physiology, signaling, and pharmacology of dopamine receptors

G protein-coupled dopamine receptors (D1, D2, D3, D4, and D5) mediate all of the physiological functions of the catecholaminergic neurotransmitter dopamine, ranging from voluntary movement and reward to hormonal regulation and hypertension. Pharmacological agents targeting dopaminergic neurotransmission have been clinically used in the management of several neurological and psychiatric disorders, including Parkinson's disease, schizophrenia, bipolar disorder, Huntington's disease, attention deficit hyperactivity disorder (ADHD(1)), and Tourette's syndrome. Numerous advances have occurred in understanding the general structural, biochemical, and functional properties of dopamine receptors that have led to the development of multiple pharmacologically active compounds that directly target dopamine receptors, such as antiparkinson drugs and antipsychotics. Recent progress in understanding the complex biology of dopamine receptor-related signal transduction mechanisms has revealed that, in addition to their primary action on cAMP-mediated signaling, dopamine receptors can act through diverse signaling mechanisms that involve alternative G protein coupling or through G protein-independent mechanisms via interactions with ion channels or proteins that are characteristically implicated in receptor desensitization, such as β-arrestins. One of the future directions in managing dopamine-related pathologic conditions may involve a transition from the approaches that directly affect receptor function to a precise targeting of postreceptor intracellular signaling modalities either directly or through ligand-biased signaling pharmacology. In this comprehensive review, we discuss dopamine receptor classification, their basic structural and genetic organization, their distribution and functions in the brain and the periphery, and their regulation and signal transduction mechanisms. In addition, we discuss the abnormalities of dopamine receptor expression, function, and signaling that are documented in human disorders and the current pharmacology and emerging trends in the development of novel therapeutic agents that act at dopamine receptors and/or on related signaling events.

Prolactinoma and hyperprolactinaemia: a transcultural comparative study between Germany as a western, liberal, industrialised country and Syria as an oriental society with a strong Islamic tradition

OBJECTIVE

Prolactinomas and hyperprolactinaemia cause hypogonadism and impairment of sexual and reproductive function. In this transcultural study, clinical characteristics of prolactinoma/hyperprolactinaemia were compared between a liberal, western, industrialised country and a more traditional, Islamic, oriental society.

METHODS

Sixty-two Syrian patients with hyperprolactinaemia were compared to 62 German patients with hyperprolactinaemia.

RESULTS

In Syria and Germany, prolactinoma and hyperprolactinaemia were more frequent in females than in males (Syria 87% females; Germany 63% females). Prolactinomas were larger in males, males were older at diagnosis in both countries. Recorded clinical symptoms were comparable, even if culturally determined differences in spontaneous reporting of and asking for symptoms might be considered. The average age of the Syrian patients at diagnosis of hyperprolactinaemia was more than 6 years lower than in the German cohort (33.4 ± 10.4 vs. 39.7 ± 17.6 years). In Germany, a variety of therapeutic regimens were applied. In Syria, bromocriptine was prescribed exclusively.

DISCUSSION AND CONCLUSION

The differences may be attributed to culturally determined differences in sexual and reproductive behaviour, i.e. sexual intercourses of young, unmarried girls and women in association to the use of oral contraceptives regulating the menstrual cycle, maternal age at first delivery and birth frequency. Exclusive prescription of bromocriptine in Syria may be associated to limited resources and the safety of bromocriptine during pregnancy.

A double pituitary adenoma presenting as a prolactin-secreting tumor with partial response to medical therapy. Case report

Double pituitary adenomas are difficult to recognize pre-operatively as only a single mass may be appreciated on imaging. We present herein a giant prolactin-secreting pituitary adenoma in a middle-aged man that had responded partially to dopamine agonist therapy. The excised specimen demonstrated a double adenoma. The prolactin-producing one displayed the expected morphological changes resulting from medical therapy, while the other, a gonadotroph adenoma, did not. The failure of tumor shrinkage can be attributed to the presence of a double adenoma, a previously unreported cause of failure of medical therapy in prolactinoma.

Bromocriptine approved as the first medication to target dopamine activity to improve glycemic control in patients with type 2 diabetes

Type 2 diabetes mellitus (T2DM) continues to rise in prevalence in the United States and worldwide. Despite advances in medical treatments for T2DM, many patients remain uncontrolled. By targeting centrally mediated pathways of glucose metabolism, bromocriptine represents a novel therapeutic option in T2DM. Several small clinical trials demonstrate improvements in insulin resistance and glycemic control. After the submission of data from four recent, large clinical trials, the US Food and Drug Administration has approved the use of bromocriptine in T2DM. We review the available data from these four trials and other published studies. Bromocriptine is a promising therapy for diabetes patients and demonstrates modest improvements in glycemic control.

Analysis of hypertrophic thyrotrophs in pituitaries of athyroid Pax8-/- mice

Thyroid hormone is important for pituitary development and maintenance. We previously reported that in the Pax8(-/-) mouse model of congenital hypothyroidism, lactotrophs are almost undetectable, whereas the thyrotrophs exhibit hyperplasia and hypertrophy. Because the latter might be caused by an overstimulation of thyrotrophs with TRH, we analyzed TRH-R1(-/-)Pax8(-/-) double-knockout mice, which miss a functional thyroid gland and the TRH transducing receptor-1 at pituitary target sites. Interestingly, in these double mutants, the hypertrophy and hyperplasia of the thyrotrophs still persist, suggesting that the phenotype is rather a direct consequence of the athyroidism of the animals. The increased expression of TSH in the Pax8(-/-) mice was paralleled by a strongly up-regulated expression of deiodinase type 2 (Dio2) in thyrotrophic cells. Moreover, coexpression of TSH and Dio2 could also be demonstrated in the pituitary of wild-type mice, underlining the important role of this enzyme in the negative feedback regulation of TSH by thyroid hormone. As another consequence of the athyroidism in the mutant mice, tyrosine hydroxylase mRNA expression was found to be also highly up-regulated in thyrotrophic cells of the pituitaries from Pax8(-/-) mice, whereas the transcript levels in the hypothalamus were not affected. Accordingly, tyrosine hydroxylase protein levels, enzyme activities, and ultimately dopamine concentrations were found to be strongly increased in the pituitaries of Pax8(-/-) mice compared with wild-type animals. These findings may explain in part the reduced number of lactotrophs found in the pituitary of athyroid Pax8(-/-) mice and suggest a novel paracrine regulatory mechanism of lactotroph activity.

Cabergoline decreases alcohol drinking and seeking behaviors via glial cell line-derived neurotrophic factor

BACKGROUND

Cabergoline is an ergotamine derivative that increases the expression of glial cell line-derived neurotrophic factor (GDNF) in vitro. We recently showed that GDNF in the ventral tegmental area (VTA) reduces the motivation to consume alcohol. We therefore set out to determine whether cabergoline administration decreases alcohol-drinking and -seeking behaviors via GDNF.

METHODS

Reverse transcription polymerase chain reaction (RT-PCR) and Enzyme-Linked ImmunoSorbent Assay (ELISA) were used to measure GDNF levels. Western blot analysis was used for phosphorylation experiments. Operant self-administration in rats and a two-bottle choice procedure in mice were used to assess alcohol-drinking behaviors. Instrumental performance tested during extinction was used to measure alcohol-seeking behavior. The [35S]GTPgammaS binding assay was used to assess the expression and function of the dopamine D2 receptor (D2R).

RESULTS

We found that treatment of the dopaminergic-like cell line SH-SY5Y with cabergoline and systemic administration of cabergoline in rats resulted in an increase in GDNF level and in the activation of the GDNF pathway. Cabergoline treatment decreased alcohol-drinking and -seeking behaviors including relapse, and its action to reduce alcohol consumption was localized to the VTA. Finally, the increase in GDNF expression and the decrease in alcohol consumption by cabergoline were abolished in GDNF heterozygous knockout mice.

CONCLUSIONS

Together, these findings suggest that cabergoline-mediated upregulation of the GDNF pathway attenuates alcohol-drinking behaviors and relapse. Alcohol abuse and addiction are devastating and costly problems worldwide. This study puts forward the possibility that cabergoline might be an effective treatment for these disorders.

GDNF--a potential target to treat addiction

The glial cell line-derived neurotrophic factor (GDNF) is a secreted protein, best known for its role in the development of the central and peripheral nervous systems and the survival of adult dopaminergic neurons. More recently, accumulating evidence suggests that GDNF plays a unique role in negatively regulating the actions of drugs of abuse. In this article, we review these data and highlight the possibility that the GDNF pathway may be a promising target for the treatment of addiction.

Treatment with low doses of cabergoline is not associated with increased prevalence of cardiac valve regurgitation in patients with hyperprolactinaemia

INTRODUCTION AND AIM

Dopamine agonists have been reported to increase the risk of cardiac valve regurgitation in patients with Parkinson's disease. However, it is unknown whether these drugs might be harmful for patients with hyperprolactinaemia (HyperPRL). The aim of the study was to evaluate whether HyperPRL patients treated with dopamine agonists had a higher prevalence of cardiac valves regurgitation than that of general population.

METHODS AND PATIENTS

One hundred consecutive patients (79 women, 21 men, mean age 41 +/- 13 years) with HyperPRL during treatment with cabergoline were enrolled in an observational case-control study and compared with 100 matched normal subjects (controls). Valve regurgitation was assessed by echocardiography according to the American Society of Echocardiography recommendations.

RESULTS

Seven HyperPRL patients (7%) and six controls (6%) had moderate (grade 3) regurgitation in any valve (p = 0.980). All were asymptomatic and had no signs of cardiac disease. Mean duration of cabergoline treatment was 67 +/- 39 months (range: 3-199 months). Mean cumulative dose of cabergoline was 279 +/- 301 mg (range: 15-1327 mg). Moderate valve regurgitation was not associated with the duration of treatment (p = 0.359), with cumulative dose of cabergoline (p = 0.173), with age (p = 0.281), with previous treatment with bromocriptine (p = 0.673) or previous adenomectomy (p = 0.497) in patients with HyperPRL.

DISCUSSION

In conclusion, treatment with cabergoline was not associated with increased prevalence of cardiac valves regurgitation in patients with HyperPRL. Mean cumulative dose of cabergoline was lower in patients with HyperPRL than that reported to be deleterious for patients with Parkinson's disease: hence, longer follow-up is necessary, particularly in patients receiving weekly doses > 3 mg.

Cabergoline therapy and the risk of cardiac valve regurgitation in patients with hyperprolactinemia: a meta-analysis from clinical studies

Dopamine agonists have been associated with increased risk of cardiac valve regurgitation in patients with Parkinson's disease. Whether these drugs might be harmful for patients with hyperprolactinemia is still unsettled. Occasional case reports and 7 studies on the relationship between cabergoline and cardiac valve regurgitation have been published so far. Overall, cabergoline has been considered a safe therapy, although some studies suggested an increased prevalence of cardiac valve regurgitation. The aim of this meta-analysis was to assess the effects of cabergoline on cardiac valve regurgitation. Eligible studies were all trials using cabergoline in patients with either tumor or non-tumor hyperprolactinemia. Our search was updated to October 2008. Pooled data from the 6 selected studies showed that treatment with cabergoline was associated with increased risk of tricuspid valve regurgitation (fixed effects: prevalence ratio=1.40; 95% confidence interval: 1.17-1.67); on the contrary, patients treated with cabergoline and control subjects did not differ in prevalence of aortic or mitral valve regurgitation. This meta-analysis shows that patients with hyperprolactinemia treated with cabergoline are at increased risk of regurgitation of the tricuspid valve. However, regurgitation was only an echocardiographic finding since no patient had symptoms of valvular disease. This meta-analysis underscores that echocardiography is recommended in all patients with hyperprolactinemia who are candidate to be treated with or are under cabergoline therapy; monitoring cardiac valves is also recommended although precise follow- up for these patients will be likely provided by future longitudinal studies.

Cabergoline: Pharmacology, ocular hypotensive studies in multiple species, and aqueous humor dynamic modulation in the Cynomolgus monkey eyes

The aims of the current studies were to determine the in vitro and in vivo ocular and non-ocular pharmacological properties of cabergoline using well documented receptor binding, cell-based functional assays, and in vivo models. Cabergoline bound to native and/or human cloned serotonin-2A/B/C (5HT(2A/B/C)), 5HT(1A), 5HT(7), alpha(2B), and dopamine-2/3 (D(2/3)) receptor subtypes with nanomolar affinity. Cabergoline was an agonist at human recombinant 5HT(2), 5HT(1A) and D(2/3) receptors but an antagonist at 5HT(7) and alpha(2) receptors. In primary human ciliary muscle (h-CM) and trabecular meshwork (h-TM) cells, cabergoline stimulated phosphoinositide (PI) hydrolysis (EC(50)=19+/-7 nM in TM; 76 nM in h-CM) and intracellular Ca(2+) ([Ca(2+)](i)) mobilization (EC(50)=570+/-83 nM in h-TM; EC(50)=900+/-320 nM in h-CM). Cabergoline-induced [Ca(2+)](i) mobilization in h-TM and h-CM cells was potently antagonized by a 5HT(2A)-selective antagonist (M-100907, K(i)=0.29-0.53 nM). Cabergoline also stimulated [Ca(2+)](i) mobilization more potently via human cloned 5HT(2A) (EC(50)=63.4+/-10.3 nM) than via 5HT(2B) and 5HT(2C) receptors. In h-CM cells, cabergoline (1 microM) stimulated production of pro-matrix metalloproteinases-1 and -3 and synergized with forskolin to enhance cAMP production. Cabergoline (1 microM) perfused through anterior segments of porcine eyes caused a significant (27%) increase in outflow facility. Topically administered cabergoline (300-500 microg) in Dutch-belted rabbit eyes yielded 4.5 microMM and 1.97 microM levels in the aqueous humor 30 min and 90 min post-dose but failed to modulate intraocular pressure (IOP). However, cabergoline was an efficacious IOP-lowering agent in normotensive Brown Norway rats (25% IOP decrease with 6 microg at 4h post-dose) and in conscious ocular hypertensive cynomolgus monkeys (peak reduction of 30.6+/-3.6% with 50 microg at 3h post-dose; 30.4+/-4.5% with 500 microg at 7h post-dose). In ketamine-sedated monkeys, IOP was significantly lowered at 2.5h after the second topical ocular dose (300 microg) of cabergoline by 23% (p<0.02) and 35% (p<0.004) in normotensive and ocular hypertensive eyes, respectively. In normotensive eyes, cabergoline increased uveoscleral outflow (0.69+/-0.7 microL/min-1.61+/-0.97 microL/min, n=13; p<0.01). However, only seven of the eleven ocular hypertensive monkeys showed significantly increased uveoscleral outflow. These data indicate that cabergoline's most prominent agonist activity involves activation of 5HT(2), 5HT(1A), and D(2/3) receptors. Since 5HT(1A) agonists, 5HT(7) antagonists, and alpha(2) antagonists do not lower IOP in conscious ocular hypertensive monkeys, the 5HT(2) and dopaminergic agonist activities of cabergoline probably mediated the IOP reduction observed with this compound in this species.

Relevance of coexpression of somatostatin and dopamine D2 receptors in pituitary adenomas

Dopamine and somatostatin are both involved in the negative control of normal pituitary cells. Dopamine subtype 2 receptor (D2DR) and somatostatin receptor (sst) agonists, mainly directed to sst2, are used in the treatment of pituitary adenomas. Nevertheless, a majority of corticotroph and gonadotroph adenomas and a third of somatotroph adenomas are still not sufficiently controlled by these treatments. D2DR and sst1, 2, 3 and 5 are present in most pituitary adenomas. These receptors may interact by heterodimerization as shown for sst1-sst5, sst5-D2DR, sst2-sst3 and sst2-D2DR suggesting possible additive effects. D2DR and sst2 agonist cotreatment showed limited additivity on GH secretion in acromegaly. Moreover, new chimeric compounds with sst2, D2DR and sst5 affinity have shown an increased control of secretion and/or proliferation of different types of pituitary adenomas in cell culture. Together with the multi-sst ligand drugs recently developed, these dopamine-somatostatin ligands represent a new opportunity in the combinatory treatment of pituitary adenomas.

Caveolin-1 sensitizes rat pituitary adenoma GH3 cells to bromocriptine induced apoptosis

BACKGROUND

Prolactinoma is the most frequent pituitary tumor in humans. The dopamine D2 receptor agonist bromocriptine has been widely used clinically to treat human breast tumor and prolactinoma through inhibition of hyperprolactinemia and induction of tumor cell apoptosis, respectively, but the molecular mechanism of bromocriptine induction of pituitary tumor apoptosis remains unclear. Caveolin-1 is a membrane-anchored protein enriched on caveolae, inverted flask-shaped invaginations on plasma membranes where signal transduction molecules are concentrated. Currently, caveolin-1 is thought to be a negative regulator of cellular proliferation and an enhancer of apoptosis by blocking signal transduction between cell surface membrane receptors and intracellular signaling protein cascades. Rat pituitary adenoma GH3 cells, which express endogenous caveolin-1, exhibit increased apoptosis and shrinkage after exposure to bromocriptine. Hence, the GH3 cell line is an ideal model for studying the molecular action of bromocriptine on prolactinoma.

RESULTS

The expression of endogenous caveolin-1 in GH3 cells was elevated after bromocriptine treatment. Transiently expressed mouse recombinant caveolin-1 induced apoptosis in GH3 cells by enhancing the activity of caspase 8. Significantly, caveolin-1 induction of GH3 cell apoptosis was sensitized by the administration of bromocriptine. Phosphorylation of caveolin-1 at tyrosine 14 was enhanced after bromocriptine treatment, suggesting that bromocriptine-induced phosphorylation of caveolin-1 may contribute to sensitization of apoptosis in GH3 cells exposed to bromocriptine.

CONCLUSION

Our results reveal that caveolin-1 increases sensitivity for apoptosis induction in pituitary adenoma GH3 cells and may contribute to tumor shrinkage after clinical bromocriptine treatment.