Dopamine agonist therapy for hyperprolactinemia

Formal Synthesis of (-)-Quinagolide: Diastereoselective Ring Expansion via a Bicyclic Aziridinium Ion Strategy to Access the Octahydrobenzo[g]quinoline Architecture

The diastereoselective formal synthesis of (-)-quinagolide, a D₂ receptor agonist, has been achieved. The synthesis started from l-pyroglutamic acid and relied on utilization of (a) a stereospecific catalytic hydrogenation and diastereoselective Horner-Emmons-Michael cascade to obtain functionalized prolinate, (b) a Lewis acid mediated Pummerer cyclization to construct a tricyclic fused ring system, and (c) a diastereoselective ring expansion via a bicyclic aziridinium intermediate to access the required 3-substituted piperidine scaffold.

An assessment of serum prolactin levels among infertile women with galactorrhea attending a gynecological clinic North-West Nigeria

Background:

Galactorrhea is a common manifestation of hyperprolactinemia but may not always be present in women with hyperprolactinemia. This study was, therefore, undertaken to assess the serum prolactin levels of infertile women presenting with galactorrhea and to determine the prevalence of hyperprolactinemia among them.

Materials and Methods:

This was a retrospective study of serum prolactin levels of 63 female partners of infertile couples attending the gynecological clinic of Federal Medical Centre, Birnin Kudu, Jigawa State, Nigeria, who were found to have galactorrhea from January 1, 2012, to December 31, 2013. Ethical clearance was obtained. Solid phase enzyme-linked immunosorbent assay was used to measure serum prolactin. Sociodemographic characteristics were determined. The data obtained were analyzed using SPSS version 17.0 statistical software. Absolute numbers and simple percentages were used to describe categorical variables. Similarly, quantitative variables were described using measures of central tendency (mean, median) and measures of dispersion (range, standard deviation) as appropriate.

Results:

The average age of the women was 27.9 ± 5.6 years. In half of the cases (50%), galactorrhea was associated with menstrual disturbances, mainly amenorrhea (23.3%). Although most (63.3%) of the clients had normal serum prolactin level despite being galactorrheic, averagely there was a marked elevation in serum prolactin of as high as 40.3 ± 52.3 ng/mL.

Conclusion:

We conclude, therefore, that the prevalence of hyperprolactinemia in this study was low when compared with other studies and that galactorrhea does not always indicate raised serum prolactin levels.

Managing Prolactinomas during Pregnancy

Prolactinomas are the most prevalent functional benign pituitary tumors due to a pituitary micro- or macroadenoma. The majority of patients presents with infertility and gonadal dysfunction. A dopamine agonist (DA) (bromocriptine or cabergoline) is the treatment of choice that can normalize prolactin levels, reduce tumor size, and restore ovulation and fertility. Cabergoline generally preferred over bromocriptine because of its higher efficacy and tolerability. Managing prolactinomas during pregnancy may be challenging. During pregnancy, the pituitary gland undergoes global hyperplasia due to a progressive increase in serum estrogens level that may lead to increase of the tumor volume with potential mass effect and visual loss. The risk of tumor enlargement may occur in 3% of those with microadenomas, 32% in those with macroadenomas that were not previously operated on, and 4.8% of those with macroadenomas with prior ablative treatment. Though both drugs appear to be safe during pregnancy, the data on fetal exposure to DAs during pregnancy have been reported with bromocriptine far exceeds that of cabergoline with no association of increased risk of pregnancy loss and premature delivery. It is advisable to stop the use of DAs immediately once pregnancy is confirmed, except in the case of women with invasive macroprolactinomas or pressure symptoms. This review outlines the therapeutic approach to prolactinoma during pregnancy, with emphasis on the safety of available DA therapy.

Dopamine blocks stress-mediated ovarian carcinoma growth

PURPOSE

Increased adrenergic activity in response to chronic stress is known to promote tumor growth by stimulating the tumor microenvironment. The focus of the current study was to determine whether dopamine, an inhibitory catecholamine, could block the effects of chronic stress on tumor growth.

EXPERIMENTAL DESIGN

Expression of dopamine receptors (DR1-DR5) was analyzed by reverse transcriptase-PCR and by Western blotting. In vitro effects of dopamine on cell viability, apoptosis, and migration were examined. For in vivo therapy, murine and human DR2-siRNAs were incorporated into chitosan nanoparticles (CH-NP).

RESULTS

In this model of chronic stress, tumoral norepinephrine levels remained elevated whereas dopamine levels were significantly decreased compared with nonstressed animals. Daily restraint stress resulted in significantly increased tumor growth in both immunodeficient (SKOV3ip1 and HeyA8) and immunocompetent (ID8) ovarian cancer models. This increase was completely blocked with daily dopamine treatment. Dopamine treatment also blocked the stress-induced increase in angiogenesis. Endothelial and ovarian cancer cells expressed all dopamine receptors except for the lack of DR3 expression in ovarian cancer cells. DR2 was responsible for the inhibitory effects of dopamine on tumor growth and microvessel density as well as the stimulatory effect on apoptosis, as the DR2 antagonist eticlopride reversed these effects. Dopamine significantly inhibited cell viability and stimulated apoptosis in vitro. Moreover, dopamine reduced cyclic AMP levels and inhibited norepinephrine and vascular permeability factor/VEGF-induced Src kinase activation.

CONCLUSIONS

Dopamine depletion under chronic stress conditions creates a permissive microenvironment for tumor growth that can be reversed by dopamine replacement.

Adverse endocrine and metabolic effects of psychotropic drugs: selective clinical review

The article critically reviews selected, clinically significant, adverse endocrine and metabolic effects associated with psychotropic drug treatments, including hyperprolactinaemia, hyponatraemia, diabetes insipidus, hypothyroidism, hyperparathyroidism, sexual dysfunction and virilization, weight loss, weight gain and metabolic syndrome (type 2 diabetes mellitus, dyslipidaemia and hypertension). Such effects are prevalent and complex, but can be managed clinically when recognized. They encourage continued critical assessment of benefits versus risks of psychotropic drugs and underscore the importance of close coordination of psychiatric and general medical care to improve long-term health of psychiatric patients. Options for management of hyperprolactinaemia include lowering doses, switching to agents such as aripiprazole, clozapine or quetiapine, managing associated osteoporosis, carefully considering the use of dopamine receptor agonists and ruling out stress, oral contraceptive use and hypothyroidism as contributing factors. Disorders of water homeostasis may include syndrome of inappropriate antidiuretic hormone (SIADH), managed by water restriction or slow replacement by hypertonic saline along with drug discontinuation. Safe management of diabetes insipidus, commonly associated with lithium, involves switching mood stabilizer and consideration of potassium-sparing diuretics. Clinical hypothyroidism may be a more useful marker than absolute cut-offs of hormone values, and may be associated with quetiapine, antidepressant and lithium use, and managed by thyroxine replacement. Hyper-parathyroidism requires comprehensive medical evaluation for occult tumours. Hypocalcaemia, along with multiple other psychiatric and medical causes, may result in decreased bone density and require evaluation and management. Strategies for reducing sexual dysfunction with psychotropics remain largely unsatisfactory. Finally, management strategies for obesity and metabolic syndrome are reviewed in light of the recent expert guidelines, including risk assessment and treatments, such as monoamine transport inhibitors, anticonvulsants and cannabinoid receptor antagonists, as well as lifestyle changes.

Current treatment issues in female hyperprolactinaemia

High prolactin levels can occur as a physiological condition in females who are pregnant or lactating. As a pathological condition, hyperprolactinaemia is associated with gonadal dysfunction, infertility and an increased risk of long-term complications including osteoporosis. The most frequent cause of persistent hyperprolactinaemia is the presence of a micro- (<10mm diameter) or macroprolactinoma (>/=10mm). These pituitary tumours may produce an excessive amount of prolactin or disrupt the normal delivery of dopamine from the hypothalamus to the pituitary; prolactin secretion from the pituitary is inhibited by dopamine released from neurones in the hypothalamus. Medications including anti-psychotics can induce hyperprolactinaemia, while idiopathic hyperprolactinaemia accounts for 30-40% of cases. The prevalence of hyperprolactinaemia is difficult to establish as not all sufferers are symptomatic or concerned by their symptoms and may remain undiagnosed. Symptoms of hyperprolactinaemia include signs of hypogonadism, with oligomenorrhoea, amenorrhoea and galactorrhoea frequently observed. Pharmacological intervention should be considered the first line therapy and involves the use of dopamine agonists to reduce tumour size and prolactin levels. Bromocriptine has the longest history of use and is a well-established, inexpensive, safe and effective therapy option. However, bromocriptine requires multiple daily dosing and some patients are resistant or intolerant to this therapy. The two newer dopamine agonists, quinagolide and cabergoline, provide more effective and better tolerated treatments compared with bromocriptine and may offer effective therapies for bromocriptine-resistant or intolerant patients. Quinagolide can be used until pregnancy is confirmed and may result in improved compliance in females wishing to become pregnant. For patients with hyperprolactinaemia, pregnancy is safe and can frequently be beneficial, inducing a decrease in prolactin levels. There does not appear to be any increased risk of abortion, malformations or multiple births in pregnancies achieved with bromocriptine and this dopamine agonist can be used safely during pregnancy. Surgery should be considered only in certain circumstances, and for the majority of patients, dopamine agonists will be sufficient to alleviate symptoms and restore normal prolactin levels.

Treatment of pituitary tumors: dopamine agonists

The neurotransmitter/neuromodulator dopamine plays an important role in both the central nervous system and the periphery. In the hypothalamopituitary system its function is a dominant and tonic inhibitory regulation of pituitary hormone secretion including prolactin- and proopiomelanocortin-derived hormones. It is well known that dopamine agonists, such as bromocriptine, pergolide, quinagolide, cabergoline, and lisuride, can inhibit PRL secretion by binding to the D(2) dopamine receptors located on normal as well as tumorous pituitary cells. Moreover, they can effectively decrease excessive PRL secretion as well as the size of the tumor in patients having prolactinoma. Furthermore, dopamine agonists can also be used in other pituitary tumors. The major requirement for its use is that the tumor cells should express D(2) receptors. Therefore, in addition to prolactinomas, targets of dopamine agonist therapy are somatotroph tumors, nonfunctioning pituitary tumors, corticotroph pituitary tumors, Nelson's syndrome, gonadotropinomas, and thyrotropin-secreting pituitary tumors. It is also an option for the treatment of pituitary disease during pregnancy. Differences between the effectiveness and the resistance of different dopaminergic agents as well as the future perspectives of them in the therapy of pituitary tumors are discussed.