Treatment of pituitary tumors: dopamine agonists

How to manage intolerance to dopamine agonist in patients with prolactinoma

PURPOSE

Dopamine agonists (DA) are the gold-standard for prolactinoma and hyperprolactinemia treatment. Intolerance to DA leading to drug drop out occurs in 3 to 12% of cases. We provide here a review of published data about DA intolerance and present a case report concerning the use of intravaginal cabergoline.

METHODS

We review the literature on the definition, the pathogenesis, frequency and management of DA intolerance. In addition, the review provides strategies to enhance tolerability and avoid precocious clinical treatment withdrawal.

RESULTS

Cabergoline is often cited as the most tolerable DA and its side effects tend to ameliorate within days to weeks. Restarting the same drug at a lower dose or switching to another DA can be used in cases of intolerance. The vaginal route can be tried specifically if there are gastrointestinal side effects in the oral administration. Symptomatic treatment could be attempted, although mainly based on a strategy used in other diseases.

CONCLUSIONS

Due to limited data, no guidelines have been developed for the management of intolerance in DA treatment. The most frequent management is to perform transsphenoidal surgery. Nevertheless, this manuscript provides data derived from published literature and expert opinion, suggesting new approaches to this clinical issue.

Aptamer Applications in Neuroscience

Being the predominant cause of disability, neurological diseases have received much attention from the global health community. Over a billion people suffer from one of the following neurological disorders: dementia, epilepsy, stroke, migraine, meningitis, Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, Huntington's disease, prion disease, or brain tumors. The diagnosis and treatment options are limited for many of these diseases. Aptamers, being small and non-immunogenic nucleic acid molecules that are easy to chemically modify, offer potential diagnostic and theragnostic applications to meet these needs. This review covers pioneering studies in applying aptamers, which shows promise for future diagnostics and treatments of neurological disorders that pose increasingly dire worldwide health challenges.

Anatomical Basis of Clinical Manifestations Seen in Cavernous Sinus Syndrome: A Narrative Review

Pathology involving the Cavernous Sinus (CS), generally referred to as Cavernous Sinus Syndrome (CSS), can arise from vascular disorders, neoplasms, infections, and non-infectious inflammatory disorders. An acute understanding of the CS and its regional anatomical structures is therefore pertinent in expounding the highly variable clinical manifestations seen in CSS as well as laying the groundwork for surgical intervention. Though the neuroanatomy of the cavernous sinus has been substantially chronicled in literature, their correlation to clinical signs has only been minimally described. This narrative review serves to address this knowledge gap and aims to comprehensively correlate the clinical manifestations of CSS with the relevant neuroanatomy, thereby allowing medical practitioners to better navigate the diagnostic quandary. We conducted a scoping review of the literature concerning CS anatomy and CSS, complied through MEDLINE/OVID and cross-referencing of articles on PubMed and Google Scholar with the keywords cavernous sinus, cavernous sinus syndrome, clinical signs/manifestations, neuroanatomy, CS pathology, Cavernous Sinus Thrombus (CST) and cavernous sinus neoplasms/tumours.

Dopamine Prevents Ultraviolet B-induced Development and Progression of Premalignant Cutaneous Lesions through its D2 Receptors

Although the role of dopamine (DA) in malignant tumors has been reported, its function in premalignant lesions is unknown. Herein we report that the stimulation of DA D₂ receptors in endothelial cells in ultraviolet B (UVB)-induced cutaneous lesions in mice significantly reduced the tumor number, tumor burden, and malignant squamous cell carcinoma in these animals. DA D₂ receptor agonist inhibited VEGFA-dependent proangiogenic genes in vitro and in vivo. However, the mice pretreated with selective DA D₂ receptor antagonist inhibited the actions of the agonist, thereby suggesting that the action of DA was through its D₂ receptors in the endothelial cells. To our knowledge, this study is the first to report DA-mediated regulation of pathogenesis and progression of UVB-induced premalignant skin lesions. PREVENTION RELEVANCE: This investigation demonstrates the role of dopamine and its D₂ receptors in UVB induced premalignant squamous cell skin lesions and how DA through its D₂ receptors inhibits the development and progression of these lesions and subsequently prevents squamous cell carcinoma of the skin.

Sexual Functioning in Hyperprolactinemic Patients Treated With Cabergoline or Bromocriptine

BACKGROUND

Elevated prolactin levels were found to be associated with impaired sexuality.

STUDY QUESTION

The aim of the study was to compare the impact of bromocriptine and cabergoline on sexual functioning in both genders.

STUDY DESIGN

The study enrolled 39 young women and 18 young men receiving bromocriptine treatment. In 19 women and 8 men, because of poor tolerance, bromocriptine was replaced with cabergoline, whereas the remaining ones continued bromocriptine treatment.

MEASURES AND OUTCOMES

Apart from measuring serum levels of prolactin and insulin sensitivity, at the beginning of the study and 16 weeks later, all included patients completed questionnaires evaluating female or male sexual functioning (Female Sexual Function Index; International Index of Erectile Function-15).

RESULTS

Irrespective of the gender, posttreatment prolactin levels were lower in cabergoline-treated patients than in bromocriptine-treated patients. Baseline sexual functioning did not differ between patients well and poorly tolerating bromocriptine treatment. Neither in men nor in women receiving bromocriptine, posttreatment sexual functioning differed from baseline one. In both genders, cabergoline improved sexual desire. Moreover, in men, the drug improved erectile and orgasmic function, whereas in women, it improved sexual arousal. All these effects correlated with the impact of this drug on prolactin levels and on insulin sensitivity.

CONCLUSIONS

Cabergoline is superior to bromocriptine in affecting male and female sexual functioning and should be preferred in hyperprolactinemic men and women with sexual dysfunction.

Pharmacokinetics and pharmacodynamics of pergolide mesylate after oral administration in horses with pituitary pars intermedia dysfunction

Published information on the pharmacokinetic and pharmacodynamic properties of pergolide is limited. The aim of this study was to investigate the pharmacokinetic and pharmacodynamic properties of oral pergolide in horses with pituitary pars intermedia dysfunction (PPID). The study design was a nonrandomized clinical trial. Six horses with PPID diagnosed by thyrotropin-releasing hormone (TRH) stimulation tests received pergolide at 4 μg/kg for 18 d. Plasma samples for determination of pergolide and ACTH concentration were collected 0.5 h before and 2 and 12 h after each administration of pergolide. Maximum plasma concentrations after the first oral dose of pergolide (0.104-0.684 ng/mL; median 0.261 ng/mL; interquartile range [IQR] 0.184-0.416 ng/mL) were not significantly different to the maximum steady-state concentration at day 18 (0.197-0.628 ng/mL; median 0.274; IQR 0.232-0.458 ng/mL). Chronic administration was not associated with drug accumulation (R = 1.09) and pergolide concentration reached steady state within 3 d. Throughout, concentrations of pergolide fluctuated considerably, with median plasma peak concentrations more than four times higher than median trough concentrations. Plasma ACTH concentration reduced significantly within 12 h of administration with further reductions occurring up to 10 d after the initiation of treatment. Although there were parallel fluctuations in the concentrations of pergolide and ACTH, timing of ACTH measurement in relation to the administration of pergolide did not have a significant effect. Alterations in the response to TRH were identified at 8 d with no further change being identified at 18 d. A small number of horses were studied. Oral pergolide results in significant suppression of pars intermedia activity within hours. Pergolide and ACTH concentrations fluctuated in tandem although correlation was poor. Fluctuations in pergolide concentration were consistent with a terminal elimination half-life of less than 12 h. To reduce the level of fluctuation of ACTH, twice-daily dosing of pergolide may be more appropriate.

Facile preparation of a collagen-graphene oxide composite: A sensitive and robust electrochemical aptasensor for determining dopamine in biological samples

A sensitive and robust electrochemical aptasensor for determining dopamine (DA) was developed using a grass carp skin collagen-graphene oxide (GCSC-GO) composite as a transducer and a label-free aptamer as a biological recognition element for the first time. In order to fabricate this sensor, the GCSC-GO composite was firstly prepared by ultra-sonication method and characterized by atomic force microscope, infrared spectroscopy, Raman spectroscopy, and electrochemical impedance spectroscopy. Subsequently, a label-free DA-binding aptamer was immobilized through strong interaction between collagen and aptamer. The fabricated electrochemical aptasensor was used to determine DA by differential pulse voltammetry. The results indicated that the peak current changes of the developed aptasensor was linear relationship with the DA concentrations from 1 to 1000 nM, and the detection limit was 0.75 nM (S/N = 3). Moreover, the fabricated aptasensor showed high selectivity for DA. More importantly, the obtained aptasensor exhibited satisfactory recovery toward DA in human serum specimens with excellent stability.

The effect of bromocriptine treatment on sexual functioning and depressive symptoms in women with mild hyperprolactinemia

BACKGROUND

Elevated prolactin levels are associated with sexual dysfunction in women. No previous study has investigated the effect of dopamine agonists on sexual functioning in women.

METHODS

The study enrolled 30 young women with mild hyperprolactinemia (serum prolactin levels in the range between 25 and 50ng/mL), 15 of whom were later treated with bromocriptine (5-10mg daily), as well as 14 age- and weight-matched healthy women. All women completed a questionnaire evaluating female sexual function (Female Sexual Function Index - FSFI) and a questionnaire evaluating the presence and severity of depressive symptoms (Beck Depression Inventory Second Edition - BDI-II).

RESULTS

Women with mild hyperprolactinemia had a lower total FSFI score, lower scores in all domains of sexual functioning (desire, arousal, lubrication, and dyspareunia), as well as a lower total BDI-II score than control women. Bromocriptine increased the FSFI score and tended to reduce BDI-II score. Moreover, the drug normalized desire, arousal, lubrication and dyspareunia, as well as improved orgasm and sexual satisfaction and this action correlated with changes in prolactin levels and an improvement in insulin sensitivity. No changes in sexual functioning and depressive symptoms were observed in untreated women with mild hyperprolactinemia and healthy controls.

CONCLUSIONS

Bromocriptine treatment improves female sexual functioning and slightly affects depressive symptoms in women with elevated prolactin levels and this effect is related to its prolactin-lowering and metabolic effects.

Effect of Metformin on Hypothalamic-Pituitary-Thyroid Axis Activity in Elderly Antipsychotic-Treated Women With Type 2 Diabetes and Subclinical Hypothyroidism: A Preliminary Study

Metformin was found to reduce elevated serum thyrotropin levels, and this effect was partially determined by endogenous dopaminergic tone. The aim of this study was to compare the effect of metformin treatment on hypothalamic-pituitary-thyroid axis activity in elderly women with subclinical hypothyroidism treated with antipsychotic agents and not receiving this drug. The study population consisted of 34 elderly women with subclinical hypothyroidism, 16 of whom received antipsychotic drugs. Because of coexistent type 2 diabetes, these women were treated with metformin (2.55-3 g daily). Glucose homeostasis markers as well as serum levels of thyrotropin, free thyroid hormones and prolactin were measured at the beginning of the study and 6 months later. Thirty women completed the study. With the exception of prolactin, baseline serum levels of the assessed hormones were comparable in both study groups. Although metformin reduced serum thyrotropin levels in both groups, this effect was more pronounced in the antipsychotic-treated than in the antipsychotic-naive patients. The effect on serum prolactin was observed only in antipsychotic-treated patients. The impact on serum thyrotropin levels correlated with improvement in insulin sensitivity and with a reduction in prolactin levels. Free thyroxine and free triiodothyronine remained at a similar level throughout the study. The obtained results indicate that metformin reduces serum thyrotropin levels in elderly women, and this effect is particularly pronounced in women with diminished dopaminergic transmission.

The therapeutic effect of bromocriptine in combination with spironolactone in patients with primary aldosteronism: a hypothesis generating pilot study

Background

Dopamine D2-like receptors are attenuated in aldosterone producing adenoma, lead to overproduction of aldosterone in affected patients, and thus reported to serve as a potential treatment target for primary aldosteronism. The D2 dopamine receptor agonist bromocriptine has been used clinically for reducing tumor mass of pituitary adenomas of lactotroph origin. The aim of the present study was to assess the efficacy of adding bromocriptine to spironolactone in the biochemical control of primary aldosteronism.

Methods

Thirty patients (15 aldosterone producing adenoma) received bromocriptine treatment with dose titration to a daily dose of 7.5mg. Urine aldosterone and potassium excretion ratio of all patients were compared based on the result of metoclopramide test at baseline.

Results

On the basis of response to metoclopramide at baseline, the proportions of patients with lower urine aldosterone and urine potassium level after taking bromocriptine for six months were higher in the high metoclopramide response group. Initial aldosterone-renin ratio and high metoclopramide response at baseline were independent predictors of a decrease in aldosterone secretion after a six–month course of bromocriptine. The effects of bromocriptine added to spironolactone to reduce aldosterone secretion and potassium excretion in primary aldosteronism dissipated at 9 month after the initial treatment.

Conclusions

In this pilot study, we found that short-term addition of bromocriptine to spironolactone improved the biochemical control of primary aldosteronism. Dopamine agonist is more effective in patients with high baseline aldosterone-renin ratio and those sensitive to metoclopramide stimulation. However, this effect dissipated after 9 months.

Clinical trial registry information

ClinicalTrials. Gov number: NCT00451672; https://www.clinicaltrial.gov/ct2/show/NCT00451672?term=NCT00451672&rank =1; trial registry name: The Therapeutic Effect of Bromocriptin in Patients With Primary Aldosteronism.

Sex-dependent effect of metformin on hypothalamic-pituitary-thyroid axis activity in patients with subclinical hypothyroidism

BACKGROUND

Metformin was found to reduce elevated serum thyrotropin levels. No previous study has compared the effect of this drug on serum levels of thyrotropin and thyroid hormones between men and women.

METHODS

The study included 23 women and 12 men with subclinical hypothyroidism, who because of coexisting diabetes or impaired fasting glucose were treated with metformin (1.7-3.0g daily). Fasting plasma glucose levels, the homeostatic model assessment 1 of insulin resistance ratio (HOMA1-IR), glycated hemoglobin, serum levels of thyrotropin, free and total thyroid hormones and prolactin, as well as thyroid peroxidase and thyroglobulin antibodies were assessed at baseline and after 4 months of metformin treatment.

RESULTS

Baseline serum levels of thyrotropin, free thyroxine and free triiodothyronine, as well as a percentage of patients with positive thyroid peroxidase and thyroglobulin antibodies were comparable in both sexes. Metformin treatment reduced plasma glucose and insulin resistance, irrespective of the gender. However, only in women, metformin decreased serum thyrotropin levels. Neither in men nor in women, metformin affected serum levels of thyroid hormone and prolactin, as well as in the subgroups of patients with thyroiditis thyroid antibody titers.

CONCLUSIONS

The obtained results suggest that sex may determine the effect of metformin on hypothalamic-pituitary-thyroid axis activity.

The effect of short-term metformin treatment on plasma prolactin levels in bromocriptine-treated patients with hyperprolactinaemia and impaired glucose tolerance: a pilot study

Metformin was found to affect plasma levels of some pituitary hormones. This study was aimed at investigating whether metformin treatment has an impact on plasma prolactin levels in bromocriptine-treated patients with hyperprolactinaemia and impaired glucose tolerance. The study included 27 patients with hyperprolactinaemia, who had been treated for at least 6 months with bromocriptine. Based on prolactin levels, bromocriptine-treated patients were divided into two groups: patients with elevated (group A, n = 12) and patients with normal (group B, n = 15) prolactin levels. The control group included 16 age-, sex- and weight-matched hyperprolactinaemia-free individuals with impaired glucose tolerance (group C).The lipid profile, fasting plasma glucose levels, the homeostatic model assessment of insulin resistance ratio (HOMA-IR), glycated haemoglobin, as well as plasma levels of prolactin, thyrotropin and insulin-like growth factor-1 (IGF-1) were assessed at baseline and after 4 months of metformin treatment (2.55-3 g daily). In all treatment groups, metformin reduced HOMA-IR, plasma triglycerides and 2-h postchallenge plasma glucose. In patients with hyperprolactinaemia, but not in the other groups of patients, metformin slightly reduced plasma levels of prolactin, and this effect correlated weakly with the metabolic effects of this drug. Our study shows that metformin decreases plasma prolactin levels only in patients with elevated levels of this hormone. The obtained results suggest that metformin treatment may bring some benefits to hyperprolactinaemic patients with coexisting glucose metabolism disturbances already receiving dopamine agonist therapy.

Pons herniation into skull base after cabergoline therapy of giant prolactinoma

INTRODUCTION

Pons herniation after cabergoline therapy for giant prolactinoma is a complication not documented in literature.

CASE REPORT

We report a medium aged patient who developed secondary hemiparesis after 18 months of medical treatment. MRI revealed pons herniation into the clivus. There was improvement with conservative treatment. Secuencial MRIs are presented showing the tumor at the moment of the diagnosis, tumor shrinkage and pons herniation.

DISCUSSION

Some studies have shown that a significant and rapid tumor shrinkage resulting from treatment with cabergoline can occur and it is thought that some complications are related with this tumor regression, as in the presented case.

The effect of metformin on the hypothalamic-pituitary-thyroid axis in women with polycystic ovary syndrome and subclinical hypothyroidism

The effect of metformin treatment on the hypothalamic-pituitary-thyroid axis is relatively weakly understood. This study included 24 prediabetic patients with polycystic ovary syndrome and untreated subclinical hypothyroidism, 12 of whom had already been treated with bromocriptine (5.0-7.5 mg daily). The included patients received metformin (2.55 g daily) for 6 months. Glucose homeostasis markers, serum prolactin, and thyroid function tests were determined before, after 3 months, and at the end of the treatment. Beyond improving glucose homeostasis, metformin administered for 6 months reduced serum levels of thyrotropin but did not affect serum levels of total and free thyroid hormones. Thyrotropin-lowering effect of this agent was stronger in patients not treated with bromocriptine than in patients receiving this drug, and weakly correlated with an improvement in insulin sensitivity. The obtained results indicate that metformin treatment may have an impact on thyrotrope function in hypothyroid patients, probably by enhancing the effect of thyroid hormone action in the pituitary.

Synthesis and characterization of 4-(2-aminoethyl)aniline imprinted polymer as a highly effective sorbent of dopamine

The aim of the study was to develop an efficient sorbent for the separation of dopamine. 4-(2-Aminoethyl)aniline was chosen as a pseudo-template to produce the imprinted polymers from seven different functional monomers in the presence of ethylene glycol dimethacrylate as a cross-linker. The binding capacity showed that the highest binding specificity towards dopamine was achieved when methacrylic acid was used as the monomer in methanol solution to form a polymer matrix. The imprinting factor value was equal to 22.96. Other biogenic amines were bound much more weakly. A simple theoretical model was used to give an insight into the imprinting process and the selectivity of polymer matrix. Two artificial urine samples were used as the complex matrices to show the usefulness of the new sorbent for bioanalysis.

Phytoestrogens regulate the proliferation and expression of stem cell factors in cell lines of malignant testicular germ cell tumors

Phytoestrogens have been shown to exert anti-proliferative effects on different cancer cells. In addition it could be demonstrated that inhibition of proliferation is associated with downregulation of the known stem cell factors NANOG, POU5F1 and SOX2 in tumor cells. We demonstrate the potential of Belamcanda chinensis extract (BCE) and tectorigenin as anticancer drugs in cell lines of malignant testicular germ cell tumor cells (TGCT) by inhibition of proliferation and regulating the expression of stem cell factors. The TGCT cell lines TCam-2 and NTera-2 were treated with BCE or tectorigenin and MTT assay was used to measure the proliferation of tumor cells. In addition, the expression of stem cell factors was analyzed by quantitative PCR and western blot analysis. Furthermore, global expression analysis was performed by microarray technique. BCE and tectorigenin inhibited proliferation and downregulated the stem cell factors NANOG and POU5F1 in TGCT cells. In addition, gene expression profiling revealed induction of genes important for the differentiation and inhibition of oncogenes. Utilizing connectivity map in an attempt to elucidate mechanism underlying BCE treatments we found highly positive association to histone deacetylase inhibitors (HDACi) amongst others. Causing no histone deacetylase inhibition, the effects of BCE on proliferation and stem cell factors may be based on histone-independent mechanisms such as direct hyperacetylation of transcription factors. Based on these findings, phytoestrogens may be useful as new agents in the treatment of TGCT.

Prolactinomas and the eye: a clinical case and review

PURPOSE

Elevated prolactin levels may have several etiologies, one of which is a prolactinoma. Prolactinomas, the most prevalent pituitary tumors, may be more common than once described. These tumors can result in ocular complications such as vision loss and visual field defects. Prolactinomas are easily treated but need to be identified early in order to prevent more serious systemic complications.

CASE REPORT

A 24-year-old Pacific Islander male presented with sudden blurred vision and an associated visual field defect in the right eye for 4 to 6 months. After performing a magnetic resonance imaging and consultation with an endocrinologist, the patient was diagnosed with a prolactinoma. The patient was treated and demonstrated a complete recovery of visual acuity and visual field defect.

CONCLUSIONS

Prolactinomas are a common pituitary tumor characterized by an increase in prolactin levels. This review describes how prolactinomas are classified, their etiology, subsequent complications, and treatments.

Management of large aggressive nonfunctional pituitary tumors: experimental medical options when surgery and radiation fail

Pituitary adenomas are generally considered benign tumors; however, a subset of these tumors displays aggressive behavior and are not easily cured. The protocol for nonsurgical treatment of aggressive pituitary lesions is less standardized than that of other central nervous system tumors. Aggressive surgical treatment, radiation, dopamine agonists, antiangiogenic drugs, and other chemotherapeutics all have roles in the treatment of aggressive pituitary tumors. More studies are needed to improve outcomes for patients with aggressive pituitary tumors.

Effective separation of dopamine from bananas on 2-(3,4-dimethoxyphenyl)ethylamine imprinted polymer

A 2-(3,4-dimethoxyphenyl)ethylamine imprinted polymer (MIP(pt) ) was prepared via the precipitation polymerization together with a nonimprinted polymer (NIP). The morphology of particles was investigated by scanning electron microscopy and the specific surface areas were estimated by methylene blue adsorption (60.5 ± 3.5 and 36.9 ± 1.2 m(2)/g for MIP(pt) and NIP, respectively). The binding experiments were performed to determine the binding capacity of MIP(pt)/NIP particles toward dopamine. Next, the effects of solvents on loading, washing, and eluting steps were examined on solid-phase extraction (SPE). Methanol-water 85:15 v/v (loading step), methanol (washing step), and 0.04 M aqueous ammonium acetate-methanol 30:70 v/v (eluting step) were selected as the most effective systems. Described SPE protocol was successfully applied for separation of dopamine on 2-(3,4-dimethoxyphenyl)ethylamine imprinted particles. Finally, the molecularly imprinted polymer was used for determination of dopamine in spiked banana extract. The total recovery of dopamine from MIP(pt) was equal to 88.5 ± 4.6%, but from NIP was only 12.8 ± 2.3%. The developed material and method were demonstrated to be applicable for the separation of dopamine from bananas. The commercial sorbent C18 was not suitable to such application.

Spontaneous reduction of prolactinoma post cabergoline withdrawal

Prolactinomas are common pituitary tumors usually highly responsive to dopamine agonists. Around 70-90% of the prolactinomas exhibit decrease in tumor size, though variably with these agents. Uncommonly, there may be little or no shrinkage in pituitary tumor. In the absence of medical therapy, pituitary apoplexy may also result in tumor shrinkage, albeit rarely. We report here a case showing only modest reduction in prolactinoma with cabergoline given for a period of one and a half years. Surprisingly, this tumor showed a 40% reduction in the tumor size 3 months after cabergoline withdrawal in the absence of clinical or radiological evidence of apoplexy.

Brain and optic chiasmal herniations into sella after cabergoline therapy of giant prolactinoma

Optic chiasmal herniation following dopamine agonist therapy is a rare complication in patients with giant prolactinomas. But there are a few case reports of brain and chiasmal herniation following medical therapy in such cases. We report a young man who developed secondary visual loss and seizures after 6 months of medical treatment with cabergoline for giant prolactinoma. Magnetic resonance imaging of hypothalamic pituitary region revealed optic chiasmal and frontal lobe herniation into sella. There was marginal improvement in his vision after cabergoline dose reduction. The present case report highlights frontal lobe herniation in conjunction with optic chiasmal herniation as a very rare complication of medical therapy of giant prolactinoma. Different treatment options of this condition are being discussed.

Vertebral fractures in males with prolactinoma

Data on osteoporotic fractures in hyperprolactinemia are limited. An increased prevalence of radiological vertebral fractures was recently observed in women with prolactin (PRL)-secreting adenoma, whereas it is unknown whether this observation may reflect a more general increased risk of fractures in this disease and whether the prevalence of fractures in males is affected by gonadal status. Thirty-two males (median age 47 years, range: 22-79) with PRL-secreting pituitary adenoma (10 with microadenoma and 22 with macroadenoma) and 64 control males, with normal PRL values and with comparable age to patients with hyperprolactinemia, were evaluated for vertebral fractures by a morphometric approach and for bone mineral density (BMD) by a dual-energy X-ray absorptiometry at lumbar spine. Vertebral fractures were shown in 12 patients with PRL-secreting adenoma (37.5%) and in 5 controls (7.8%, P < 0.001). Fractured patients had lower BMD T-score (P = 0.007) and longer duration of disease (P < 0.001) as compared to patients who did not fracture. Fractures occurred more frequently (P = 0.03) in patients with untreated hyperprolactinemia versus patients treated with cabergoline whose frequency of vertebral fractures was still higher than control subjects. The prevalence of vertebral fractures was not significantly different between eugonadal and hypogonadal patients (33.3% vs. 38.5%; P = 0.8). Moreover, no significant (P = 0.4) difference in serum testosterone values was found between fractured and not fractured males. Hyperprolactinemia is associated with high prevalence of radiological vertebral fractures in men with PRL-secreting adenoma. These findings would also suggest that PRL excess may produce negative skeletal effects independently of hypogonadism.

Development of direct competitive enzyme-linked aptamer assay for determination of dopamine in serum

A rapid and cost-effective screening method based on a competitive enzyme-linked aptamer assay (ELAA) for dopamine (DA) in serum has been optimized and validated. In this paper, we report advantageous sensitivity and specificity of aptamer assays as compared to the existing antibody based-immunoassays. The RNA aptamer (67 mer) was immobilized via site-directed immobilization with biotin both at the 3'-end on aptamer and at neutravidin plate. Various factors such as incubation temperature, divalent ion - Mg(2+) ion and treatment of serum solution were evaluated for the performance of ELAA. The aptamer was incubated for 1h at 4°C in the assay buffer containing 5 mM Mg(2+) ion, and serum was diluted (1:9, serum:assay buffer) and filtrated through a 3 kDa dialysis membrane to extract the proteins present in the serum. Assay was performed with 0.01 μg mL(-1) of aptamer and 1.205×10(-7)M DA-HRP conjugate using the optimized method. A dose-response curve was constructed, and the limit of detection and a dynamic range for the DA were determined as 1.0×10(-12)M and four orders (1.0×10(-7)M to 5.0×10(-11) M) of magnitude, respectively. The correlation diagram of the absorbance obtained both in buffer and in serum has shown a good agreement with the correlation coefficient (R(2)=0.9872): Abs. (in serum)=0.9612×Abs. (in buffer)-0.0556. The cross-reactivity evaluation demonstrated that norepinephrine showed some cross-reactivity (3.68%) whereas 3-methoxytyramine, epinephrine, homovanillic acid and 3,4-dihydroxyphenylacetic acid showed almost no cross-reactivity (<1%). Percent recoveries of DA in serum were quite satisfactory (∼95%). This paper describes usefulness of the aptamer assay in monitoring DA in human serum.

Biogenic amines serotonin and dopamine regulate cholangiocyte hyperplastic and neoplastic growth

Biogenic amines, such as serotonin and dopamine, regulate a multitude of cellular responses. A great deal of effort has been invested into understanding the effects of these molecules and their corresponding receptor systems on cholangiocyte and cholangiocarcinoma secretion, apoptosis and growth. This review summarizes the results of these efforts and highlights the importance of these regulatory molecules on the physiology and pathophysiology of cholangiocytes. Specifically we have focused on the recent findings into the effects of serotonin and dopamine on cholangiocyte hyperplasia and neoplastic growth.

Increased local dopamine secretion has growth-promoting effects in cholangiocarcinoma

Cholangiocarcinoma is a devastating cancer of biliary origin with limited treatment options. Symptoms are usually evident after blockage of the bile duct by the tumor, and at this late stage, they are relatively resistant to chemotherapy and radiation therapy. Therefore, it is imperative that alternative treatment options are explored. We have previously shown that serotonin metabolism is dysregulated in cholangiocarcinoma leading to an increased secretion of serotonin, which has growth-promoting effects. Because serotonin and dopamine share the degradation machinery, we evaluated the secretion of dopamine from cholangiocarcinoma and its effects on cell proliferation. Using 4 cholangiocarcinoma cell lines and human biopsy samples, we demonstrated that there was an increase in mRNA and protein expression of the dopamine synthesis enzymes tyrosine hydroxylase and dopa decarboxylase in cholangiocarcinoma. There was increased dopamine secretion from cholangiocarcinoma cell lines compared to H69 and HIBEC cholangiocytes and increased dopamine immunoreactivity in human biopsy samples. Furthermore, administration of dopamine to all cholangiocarcinoma cell lines studied increased proliferation by up to 30%, which could be blocked by the pretreatment of the D2 and D4 dopamine receptor antagonists, whereas blocking dopamine production by alpha-methyldopa administration suppressed growth by up to 25%. Administration of alpha-methyldopa to nude mice also suppressed cholangiocarcinoma tumor growth. The data presented here represent the first evidence that dopamine metabolism is dysregulated in cholangiocarcinoma and that modulation of dopamine synthesis may represent an alternative target for the development of therapeutic strategies.

[Therapeutic possibilities in patients with selective pituitary resistance to thyroid hormones]

Selective pituitary resistance to thyroid hormones (SPRTH) is a non-neoplastic form of inappropriate secretion of thyrotropin (TSH). The etiology of this hormonal resistance is linked to inactivating mutations in the thyroid hormone receptor beta (TR-beta) gene. These mutations affect critical portions of the receptor's triiodothyronine (T3)-binding domain. Clinically, SPRTH is characterized by hyperthyroidism with goiter and absence of pituitary mass in the morphologic study. Laboratory data show an elevation of free T3 and free thyroxine concentrations without suppression of TSH, with normal molar subunit alpha/TSH ratio. At this time, there is no specific therapy for SPRHT. Beta blockers, such as atenolol, and benzodiazepines have been used as a symptomatic therapy. Among the drugs with the capacity for reducing TSH secretion are TR agonists, such as triiodothyroacetic acid, D-thyroxine, triiodothyropropionic acid, and L-T3.

Correlation of in vitro and in vivo somatotropic adenoma responsiveness to somatostatin analogs and dopamine agonists with immunohistochemical evaluation of somatostatin and dopamine receptors and electron microscopy

OBJECTIVE AND PATIENTS

Twenty-four pituitary adenomas from acromegalic patients (13 females, 11 males; age range 19-65 yr) were characterized for somatostatin receptor subtype 2A (sst(2A)), dopamine D(2) receptor (D(2)R), GH, and prolactin (PRL) expression by immunohistochemistry, and results correlated with the in vitro and in vivo hormone responses to octreotide and quinagolide. In nine cases, GH and PRL content was further studied by immunoelectron microscopy.

RESULTS

Immunoreactivity was semiquantitatively scored as 2 (>50% stained cells), 1 (10-50% stained cells), and 0 (<10% stained cells). Sst(2A) was scored as 2 in 13 cases, 1 in 10, and 0 in one; D(2)R was scored as 2 in 13 cases, 1 in nine, and 0 in 2; GH was 2 in 15 cases and 1 in nine; PRL was 2 in six cases, 1 in 13, and 0 in 5. Sst(2A) was positively correlated with in vitro (P = 0.003) and in vivo (P = 0.006) percent GH suppression by octreotide and with the chronic suppression of IGF-I by somatostatin analogs (P =0.008). D(2)R was positively correlated with in vitro percent GH (P =0.000) and PRL (P =0.005) suppression by quinagolide. Electron microscopy revealed two pure somatotroph adenomas, five somatomammotrophs with a variable coexpression of GH and PRL in the same cells, and two tumors consisting of mixed cell types, which were less sensitive to quinagolide and octreotide.

CONCLUSION

Sst(2A) and D(2)R are frequently coexpressed in adenomas from acromegalic patients, and immunohistochemistry may be helpful in characterizing receptor expression in pituitary adenomas to select patients responsive to different treatments.

D2 dopamine receptor-mediated antiproliferation in a small cell lung cancer cell line, NCI-H69

The D2 dopamine receptor agonist bromocriptine has been used clinically for reducing tumor mass of pituitary adenomas arising from lactotroph origins. As well, bromocriptine has been shown to have an antiproliferative effect on primary lactotrophs and lactotroph-derived cell lines. The presence of D2 dopamine-like receptors on NCI-H69 cells was previously established by the use of [(125)I]iodosulpride binding and has been confirmed in this study by use of reverse transcription PCR with receptor-specific primers. The reverse transcription PCR analysis of NCI-H69 cells demonstrates that both the D2s and D2l are expressed in NCI-H69 cells, with D2s having the higher relative expression. The activation of the D2R results in an inhibition of growth of NCI-H69 cells as assessed by the incorporation of [(3)H]thymidine; a process not sensitive to pertussis toxin. In NCI-H69 cells, the D2 dopamine-like receptor is coupled to the inhibition of forskolin-stimulated cAMP accumulation and to the stimulation of phospholipase D. The receptor-mediated inhibition of cAMP accumulation is ablated by overnight treatment with pertussis toxin but the stimulation of phospholipase D mediated by dopaminergic agonists is not. These data suggest that the phospholipase D pathway is responsible for the antiproliferative effects of D2 dopamine-like receptors agonists in small cell lung cancer cells. In support of this hypothesis, the inhibition of [(3)H]thymidine incorporation mediated by dopaminergic agonists was shown to be sensitive to the presence of ethanol. Taken together, these data suggest that the D2 dopamine-like receptor activates phospholipase D, which ultimately leads to an inhibition of growth of this small cell lung cancer cell line.

Preclinical and clinical experiences with the role of dopamine receptors in the treatment of pituitary adenomas

Pituitary tumors can cause symptoms of mass effect and hormonal hypersecretion that can be reversed with surgical resection or debulking of the adenoma, radiotherapy, or medical treatment. Medical treatment is the primary choice for prolactinomas because dopamine agonists are very effective in the treatment of these tumors, with rates of control (tumor size reduction and hormone suppression) as high as 80-90% for microprolactinomas and 60-75% for macroprolactinomas. The function of dopamine receptors in other histotypes of pituitary adenoma is still debated. However, new insights into receptor physiology and the introduction of new clinically available, as well as experimental, compounds have reopened a potential role of dopaminergic drugs in the medical treatment of pituitary tumors. The differences between the effectiveness and the resistance to different dopaminergic agents, the new challenging results from clinical and experimental studies, as well as the future of dopamine agonists in the therapy of pituitary tumors are discussed.

Temozolomide therapy in a man with an aggressive prolactin-secreting pituitary neoplasm: Morphological findings

Administration of temozolomide to a 46-year-old man with an invasive aggressive prolactin (PRL)-secreting pituitary neoplasm resulted in improvement of the clinical condition and significant decrease of blood PRL levels. Histologic, immunohistochemical, and electron microscopic study demonstrated marked morphological differences in the tumor exposed to temozolomide compared with the unexposed tumor. Necrosis, hemorrhagic areas, accumulation of connective tissue, focal inflammatory infiltration, and neuronal transformation were seen. Immunohistochemical prognostic indicators showed a reduction in growth potential. Based on the clinical, laboratory, and morphological findings, we recommend temozolomide therapy in patients with pituitary tumors not responding adequately to other treatment options.

Brain & chiasmal herniations into sella after medical treatment of prolactinoma

BACKGROUND

Dopamine agonists are widely used in the treatment of pituitary prolactinomas. We report a case of inferior mesial frontal lobe (gyrus rectus) and chiasmal herniations into an enlarged sella following successful medical treatment of a pituitary macroadenoma.

METHOD

A 71-year-old healthy man presented to medical attention with visual complaints. On examination, he was found to have bitemporal hemianopsia. Endocrine evaluation revealed an elevated prolactin level. He was treated medically with a dopamine agonist (bromocriptine).

RESULTS

Evaluation after one year of medical treatment revealed stabilization of the patient's vision, with a significant bitemporal field loss. Serum prolactin levels normalized (5.16 ng/ml). The MRI of the sella showed almost complete disappearance of the tumor, resulting in right mesial frontal lobe herniation inferiorly into an enlarged sella with associated chiasmal deformation.

CONCLUSIONS

We report a case where successful medical treatment of a large pituitary prolactinoma has resulted in inferior frontal lobe and chiasmal herniatons into an enlarged sella.