Control of prolactin secretion

Pool vs single sample determination of serum prolactin to explore venipuncture associated stress induced variation

Stress is identified as a cause of transient hyperprolactinemia, whereas venipuncture is considered a source of stress for patient. The aim of this study was to investigate the association of venipuncture-induced stress with elevation of serum prolactin. This was a cross-sectional observational study conducted on a group of 150 outdoor patients visiting a tertiary care hospital. Serial sampling was performed by drawing venous blood at different time intervals (0, 30 and 60 min) by single venipuncture to measure serum prolactin to diagnose stress-induced hyperprolactinemia. The study was conducted in two phases, namely, Phase 1 and Phase 2, at different times. The Phase 1 results were divided into two groups: Group 1 (0 min) and Group 5 (pool prepared from samples collected at 0 + 30 + 60 min). Likewise, the results of Phase 2 were segregated into five groups; Group 1 (0 min), Group 2 (30 min), Group 3 (60 min), Group 4 (average of three groups), and Group 5 (pool from samples collected at 0 + 30 + 60 min). In both Phase 1 and Phase 2 of the study, there was a statistically significant (p = 0.0003 in Phase 1 and p = 0.02 in Phase 2) decrease in the mean prolactin (17.99 ± 24.76 ng/mL in Phase 1 and 19.61 ± 23.42 ng/mL in Phase 2) in the pooled samples (Group 5) in comparison to the mean prolactin (19.67 ± 27.69 ng/mL in Phase 1 and 21.06 ± 25.06 ng/mL in Phase 2) of the serum collected at 0 h (Group 1). There was no significant difference in the mean prolactin measured from the pooled samples and average prolactin calculated after individual testing from each sample collected at 0 h, 30 min and 60 min. Venipuncture-triggered fear and apprehension may result in transient hyperprolactinemia. In comparison to performing multiple testing on the samples collected at different time intervals and determining the mean, measurement of the analyte from the pooled serum is the better alternative as it can conserve both time and resources.

Increased Serum Prolactin and Excessive Daytime Sleepiness: An Attempt of Proof-of-Concept Study

The objectives of this study were: (1) to identify subjects with hyperprolactinemia in a clinical sample of patients; (2) to compare the neurologic, psychiatric, and sleep conditions found in patients subgrouped by excessive daytime sleepiness (EDS) and hyperprolactinemia; and (3) to identify patients with hyperprolactinemia and EDS not supported by the presence of any other neurologic, psychiatric, or sleep disorder, or substance/medication use. A retrospective chart review of inpatients was carried out in order to identify all patients in whom the prolactin (PRL) serum levels were determined. A total of 130 subjects were retrieved: 55 had increased levels of PRL, while the remaining 75 participants had normal PRL levels. EDS was reported by 32 (58.2%) participants with increased PRL and 34 (45.3%) with normal PRL. Obstructive sleep apnea or other sleep or neurologic/psychiatric conditions could explain EDS in all participants with normal PRL. Among subjects with increased PRL, eight had no other neurologic/psychiatric or sleep disorder (or drug) potentially causing EDS; these participants, at polysomnography, had time in bed, sleep period time, and total sleep time longer than those with EDS associated to another condition. These findings can be considered as a preliminary indication of a role of hyperprolactinemia in EDS and represent a basis for future controlled studies able to test this hypothesis in a reliable, objective, and methodologically more appropriate way.

Increased Serum Prolactin and Excessive Daytime Sleepiness: An Attempt of Proof-of-Concept Study

The objectives of this study were: (1) to identify subjects with hyperprolactinemia in a clinical sample of patients; (2) to compare the neurologic, psychiatric, and sleep conditions found in patients subgrouped by excessive daytime sleepiness (EDS) and hyperprolactinemia; and (3) to identify patients with hyperprolactinemia and EDS not supported by the presence of any other neurologic, psychiatric, or sleep disorder, or substance/medication use. A retrospective chart review of inpatients was carried out in order to identify all patients in whom the prolactin (PRL) serum levels were determined. A total of 130 subjects were retrieved: 55 had increased levels of PRL, while the remaining 75 participants had normal PRL levels. EDS was reported by 32 (58.2%) participants with increased PRL and 34 (45.3%) with normal PRL. Obstructive sleep apnea or other sleep or neurologic/psychiatric conditions could explain EDS in all participants with normal PRL. Among subjects with increased PRL, eight had no other neurologic/psychiatric or sleep disorder (or drug) potentially causing EDS; these participants, at polysomnography, had time in bed, sleep period time, and total sleep time longer than those with EDS associated to another condition. These findings can be considered as a preliminary indication of a role of hyperprolactinemia in EDS and represent a basis for future controlled studies able to test this hypothesis in a reliable, objective, and methodologically more appropriate way.

Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health

The sodium iodide symporter (NIS) is the plasma membrane glycoprotein that mediates active iodide transport in the thyroid and other tissues, such as the salivary, gastric mucosa, rectal mucosa, bronchial mucosa, placenta and mammary glands. In the thyroid, NIS mediates the uptake and accumulation of iodine and its activity is crucial for the development of the central nervous system and disease prevention. Since the discovery of NIS in 1996, research has further shown that NIS functionality and iodine transport is dependent on the activity of the sodium potassium activated adenosine 5'-triphosphatase pump (Na+, K+-ATPase). In this article, I review the molecular mechanisms by which F inhibits NIS expression and functionality which in turn contributes to impaired iodide absorption, diminished iodide-concentrating ability and iodine deficiency disorders. I discuss how NIS expression and activity is inhibited by thyroglobulin (Tg), tumour necrosis factor alpha (TNF-α), transforming growth factor beta 1 (TGF-β1), interleukin 6 (IL-6) and Interleukin 1 beta (IL-1β), interferon-γ (IFN-γ), insulin like growth factor 1 (IGF-1) and phosphoinositide 3-kinase (PI3K) and how fluoride upregulates expression and activity of these biomarkers. I further describe the crucial role of prolactin and megalin in regulation of NIS expression and iodine homeostasis and the effect of fluoride in down regulating prolactin and megalin expression. Among many other issues, I discuss the potential conflict between public health policies such as water fluoridation and its contribution to iodine deficiency, neurodevelopmental and pathological disorders. Further studies are warranted to examine these associations.

Effects of Estradiol on Histological Parameters and Secretory Ability of Pituitary Mammotrophs in Ovariectomized Female Rats

Objective

Estrogen replacement therapy remains current as a therapeutic approach to treat menopausal symptoms and may significantly affect hormone-producing cells in the female pituitaries. The aim of this study was to examine the histological parameters of pituitary mammotrophs and prolactin secretion after chronic estradiol treatment in ovariectomized adult female rats, reflecting premature menopause.

Materials and Methods

In this experimental study, adult female Wistar rats were divided into non-ovariectomized (C), ovariectomized (OVX) and estradiol-treated ovariectomized (OVX+E) groups. Estradiol dipropionate [0.625 mg/kg body mass per day] was administered for four weeks, while the C and OVX groups received vehicle alone. Mammotrophs were identified by the peroxidase-antiperoxidase (PAP) immunohistochemical procedure, while prolactin concentrations were measured by the non-isotopic two-step assay (Delfia) method. Comparison of the differences between groups was performed using one-way analysis of variance (ANOVA) and Tukay (honest significant difference) HSD test.

Results

Ovariectomy caused significant (P<0.05) decreases in mammotroph optical density (OD), volume density (V_V) and number per mm² by 29, 27 and 34%, respectively, in comparison with the C females. In the OVX+E group, significant (P<0.05) increases in OD, cell volume, V_Vand number of mammotrophs per mm² by 181, 15%, 5.8-fold and 5.2-fold, respectively, were observed when compared to OVX animals. The serum prolactin concentration in OVX females was significantly (P<0.05) decreased by 14% in comparison to the C group, while in OVX+E females, prolactin levels were significantly (P<0.05) increased by 53% compared to the OVX controls.

Conclusion

Estradiol supplementation in ovariectomized females is followed by stimulatory histological and secretory changes of the mammotrophs. These results could serve as indicators of possible prolactinome development upon estradiol application in premature menopausal subjects.

Hyperprolactinaemia - a problem in patients from the reproductive period to the menopause

Hyperprolactinaemia especially affects women in reproductive age (90/100,000) but also often is diagnosed in menopause age and leads to disturbances in functioning of LH-RH neurons and, as a consequence, to a decrease of FSH and LH, which causes inhibition of oestradiol production. Prolactin is a peptide hormone, phylogenetically one of the oldest, stimulating cells of various organs, which is produced and secreted mainly by lactotrophic acidophilic cells of the anterior lobe of the pituitary. It influences the increase in the mass of the mammary glands, and stimulation and maintenance of lactation after delivery. There are a number of factors apart of pregnancy, delivery, and lactation than can influence secretion of the hormone in other physiological and pathological circumstances, like high-protein diet, stress, REM sleep, or neoplastic tumours, inflammatory diseases, chronic systematic diseases, thyroid hormonal changes, and drug intake. The purpose of this review is to summarise the current knowledge regarding the proper diagnosis and possible influence of hyperprolactinaemia on fertility and menopause symptoms and current treatment methods.

Spanish consensus on the risks and detection of antipsychotic drug-related hyperprolactinaemia

INTRODUCTION

Iatrogenic hyperprolactinaemia (IHPRL) has been more frequently related to some antipsychotic drugs that provoke an intense blockade of dopamine D2 receptors. There is a wide variation in clinical practice, and perhaps some more awareness between clinicians is needed. Due to the high frequency of chronic treatment in severe mental patients, careful attention is recommended on the physical risk. IHPRL symptoms could be underestimated without routine examination.

METHODOLOGY

An intense scientific literature search was performed in order to draw up a multidisciplinary consensus, including different specialists of psychiatry, endocrinology, oncology and internal medicine, and looking for a consensus about clinical risk and detection of IHPRL following evidence-based medicine criteria levels (EBM I- IV).

RESULTS

Short-term symptoms include amenorrhea, galactorrhoea, and sexual dysfunction with decrease of libido and erectile difficulties related to hypogonadism. Medium and long-term symptoms related to oestrogens are observed, including a decrease bone mass density, hypogonadism, early menopause, some types of cancer risk increase (breast and endometrial), cardiovascular risk increase, immune system disorders, lipids, and cognitive dysfunction. Prolactin level, gonadal hormones and vitamin D should be checked in all patients receiving antipsychotics at baseline although early symptoms (amenorrhea-galactorrhoea) may not be observed due to the risk of underestimating other delayed symptoms that may appear in the medium term. Routine examination of sexual dysfunction is recommended due to possible poor patient tolerance and low compliance. Special care is required in children and adolescents, as well as patients with PRL levels >50ng/ml (moderate hyperprolactinaemia). A possible prolactinoma should be investigated in patients with PRL levels >150ng/ml, with special attention to patients with breast/endometrial cancer history. Densitometry should be prescribed for males >50 years old, amenorrhea>6 months, or early menopause to avoid fracture risk.

Rotating night shift work, sleep quality, selected lifestyle factors and prolactin concentration in nurses and midwives

The pattern of secretion of many hormones, including prolactin, is dependent on the circadian rhythm. Night shift work involves exposure to artificial light at night and sleep deficiency, which in turn can affect prolactin synthesis. The aim of this study was to evaluate a possible association between night shift work characteristics, sleep quality, lifestyle factors and prolactin concentration, using data from a cross-sectional study of nurses and midwives. A cross-sectional study was conducted among 327 nurses and midwives currently working on rotating night shifts, and 330 nurses and midwives working during the day (aged 40-60 years) (388 premenopausal and 269 postmenopausal). Information about night shift work characteristics, lifestyle, reproductive factors, sleep pattern and other covariates was collected through a face-to-face interview, and from a one-week work and sleep diary completed by the subjects. Weight and height were measured. Prolactin concentration was measured in the morning blood sample using the electrochemiluminesence immunoassay method. Associations were analyzed using linear regression models adjusted for important confounders. Analyses were carried out separately in pre- and postmenopausal women. None of the night shift work or sleep characteristics was significantly associated with prolactin concentration. Prolactin concentration was significantly (p < 0.05) inversely associated with smoking and time of blood sample collection. These results were consistent among both pre- and postmenopausal women. Nulliparity was significantly positively associated with prolactin among premenopausal women, but inversely among postmenopausal. Age was related to prolactin among postmenopausal women only. Our study indicates that rotating night shift work is not associated with prolactin concentration. Smoking, parity, time of blood collection and age among postmenopausal women were significant determinants of prolactin.

Pharmacological overview of galactogogues

Galactogogues are substances used to induce, maintain, and increase milk production, both in human clinical conditions (like noninfectious agalactias and hypogalactias) and in massification of production in the animal dairy industry. This paper aims to report the state of the art on the possible mechanisms of action, effectiveness, and side effects of galactogogues, including potential uses in veterinary and human medicine. The knowledge gaps in veterinary clinical practice use of galactogogues, especially in the standardization of the lactogenic dose in some pure drugs and herbal preparations, are reviewed.

Establishment of reference interval of serum prolactin in an Indian population

BACKGROUND

Reference data on serum prolactin levels based on a representative Indian sample are still lacking. The western normative laboratory values used for clinical diagnosis may not be applicable to Indian population. The objective of the study was to measure the serum prolactin levels in healthy Indian male and female in order to establish reference interval and to compare with the available reference intervals. It is a cross- sectional study done in West Bengal, India.

MATERIALS AND METHODS

Based on the history, clinical examination and laboratory investigations, serum prolactin levels of 1316 apparently healthy subjects were estimated by microplate immunoenzymometric assay using pooled serum. Statistical analysis was performed using SPSS software.

RESULTS

The serum prolactin levels for all ages were 10.7 ± 3 ng/ml in healthy male and 11.6 ± 2.8 ng/ml in healthy female. Decade-wise analysis of serum prolactin level in female showed a steady increase from 20-29 years to advancing decades until 4(th) decade and thereafter declines steadily although it was not same for male.

CONCLUSION

Our study will help each laboratory to formulate their own reference interval for prolactin. As of now they were dependent either on the values written on the kit-literature supplied by the reagent manufacturing company or the reference intervals of foreign population.

Hyperprolactinemia

Prolactin (PRL) is an anterior pituitary hormone which has its principle physiological action in initiation and maintenance of lactation. In human reproduction, pathological hyperprolactinemia most commonly presents as an ovulatory disorder and is often associated with secondary amenorrhea or oligomenorrhea. Galactorrhea, a typical symptom of hyperprolactinemia, occurs in less than half the cases. Out of the causes of hyperprolactinemia, pituitary tumors may be responsible for almost 50% of cases and need to be investigated especially in the absence of history of drug induced hyperprolactinemia. In women with hyperprolactinemic amenorrhea one important consequence of estrogen deficiency is osteoporosis, which deserves specific therapeutic consideration. Problem in diagnosing and treating hyperprolactinemia is the occurrence of the ‘big big molecule of prolactin’ that is biologically inactive (called macroprolactinemia), but detected by the same radioimmunoassay as the biologically active prolactin. This may explain many cases of very high prolactin levels sometimes found in normally ovulating women and do not require any treatment. Dopamine agonist is the mainstay of treatment. However, presence of a pituitary macroadenoma may require surgical or radiological management.

A new logical insight and putative mechanism behind fluoxetine-induced amenorrhea, hyperprolactinemia and galactorrhea in a case series

With the exception of fluoxetine, all selective serotonin reuptake inhibitors (SSRIs) commonly cause hyperprolactinemia through presynaptic mechanisms indirectly via 5-hydroxytryptamine (5-HT)-mediated inhibition of tuberoinfundibular dopaminergic neurons. However, there is little insight regarding the mechanisms by which fluoxetine causes hyperprolactinemia via the postsynaptic pathway. In this text, analysis of five spontaneously reported clinical cases of hyperprolactinemia resulting in overt symptoms of amenorrhea with or without galactorrhea, were scrupulously analyzed after meticulously correlating relevant literature and an attempt was made to explore the putative postsynaptic pathway of fluoxetine inducing hyperprolactinemia. Hypothetically, serotonin regulates prolactin release either by increasing oxytocin (OT) level via direct stimulation of vasoactitive intestinal protein (VIP) or indirectly through stimulation of GABAergic neurons. The pharmacodynamic exception and pharmacokinetic aspect of fluoxetine are highlighted to address the regulation of prolactin release via serotonergic pathway, either directly through stimulation of prolactin releasing factors (PRFs) VIP and OT via 5-HT2A receptors predominantly on PVN (neurosecretory magnocellular cell) or through induction of 5-HT1A-mediated direct and indirect GABAergic actions. Prospective molecular and pharmacogenetic studies are warranted to visualize how fluoxetine regulate neuroendocrine system and cause adverse consequences, which in turn may explore new ways of approach of drug development by targeting the respective metabolic pathways to mitigate these adverse impacts.

Decreased prolactin levels reduce parental commitment, egg temperatures, and breeding success of incubating male Adélie penguins

Hormones regulate many aspects of an individual's phenotype, including various physiological and behavioral traits. Two hormones have been described as important players in the regulation of parental investment in birds: the glucocorticoid hormone corticosterone and prolactin, a pituitary hormone, widely involved in mediating parental behavior. In comparison with corticosterone, the role of prolactin on parental investment remains poorly documented, and most studies so far have been correlative. In this study, the effects of an experimental decrease of prolactin levels on the incubation behavior of a long-lived seabird species were assessed. Male Adélie penguins were treated with self-degradable bromocriptine pellets, inhibiting prolactin secretion. Filming and subsequent video analysis allowed the determination of a behavioral time budget for birds and their position on the nest, while dummy eggs recorded incubation parameters. Incubation duration and breeding success at hatching were also monitored. As expected, bromocriptine-treatment significantly decreased plasma prolactin levels, but did not affect corticosterone levels. The behavioral time budget of penguins was not affected by the treatment. However, treated birds spent significantly more time in an upright position on the nest. These birds also incubated their eggs at lower temperatures and turned their eggs more frequently than controls, resulting in a lengthened incubation period. Despite this, the treatment was insufficient to trigger nest desertion and eggs of treated birds still hatched, indicating that several endocrine signals are required for the induction of nest abandonment. We suggest that the decreased prolactin levels in treated birds offset their timeline of breeding, so that birds displayed behavior typical of early incubation.

Diabetic db/db mice exhibit central nervous system and peripheral molecular alterations as seen in neurological disorders

The db/db mouse is a widely used preclinical model in diabetes research. Recent studies have shown that these mice also display aspects of psychosis and depression-like behaviors as seen in some psychiatric disorders. Here, we have performed multiplex immunoassay and liquid chromatography mass spectrometry profiling of the plasma and brain samples from db/db and control mice to identify altered pathways, which could be related to these behavioral abnormalities. This is the first study to carry out profiling of the brain proteome in this model. Plasma from the db/db mice had increased levels of leptin and insulin, decreased levels of peptide YY, glucagon and prolactin and alterations in inflammation-related proteins, compared with control mice. Frontal cortex tissue from the db/db mice showed changes in proteins involved in energy metabolism, cellular structure and neural functioning, and the hippocampus had changes in proteins involved in the same pathways, with additional effects on cellular signalling proteins. The overlap of these findings with effects seen in type 2 diabetes, schizophrenia, major depressive disorder and Alzheimer's disease might contribute to a common endophenotype seen in metabolic and neurological disorders.

Prolactin in men's health and disease

PURPOSE OF REVIEW

To review physiology of prolactin (PRL), cause and managment of hyperprolactinemia, and discuss evolving diverse roles of PRL in men's health.

RECENT FINDINGS

Hyperprolactinemia can be physiologically found after sexual activities, exercise, lactation, during pregnancy, and after stressful venipuncture. Elevated PRL can be caused by medications use, renal failure, hypothyroidism, and by prolactinoma - PRL secreting tumors. Symptomatic hyperprolactinemia and prolactinomas should be treated to lower PRL levels, decrease tumor size, and restore gonadal function. Three modes of treatment are typically utilized: pharmacological, radiosurgery with gamma radiation, and external beam radiation. Pharmacological treatment of prolactinomas is mainly based on dopamine agonists. The most frequently used dopamine agonists are bromocriptine and cabergoline. Cabergoline becoming the preferred drug in the treatment of prolactinomas because of higher response rate and less side-effects. Bromocriptine has been recently approved to improve glycemic control in diabetes mellitus.

SUMMARY

PRL plays a diverse role in men's reproduction and health. Detecting and treating elevated PRL may not only improve infertility and hypogonadism but also have a positive effect on the metabolic profile of patient and control of glycemic control and metabolic profile - an important advantage considering dramatic and worldwide increase in obesity and diabetes.

Estrogen action and prostate cancer

Early work on the hormonal basis of prostate cancer focused on the role of androgens, but more recently estrogens have been implicated as potential agents in the development and progression of prostate cancer. In this article, we review the epidemiological, laboratory and clinical evidence that estrogen may play a causative role in human prostate cancer, as well as rodent and grafted in vivo models. We then review recent literature highlighting potential mechanisms by which estrogen may contribute to prostate cancer, including estrogenic imprinting and epigenetic modifications, direct genotoxicity, hyperprolactinemia, inflammation and immunologic changes, and receptor-mediated actions. We discuss the work performed so far separating the actions of the different known estrogen receptors (ERs), ERα and ERβ, as well as G-protein-coupled receptor 30 and their specific roles in prostate disease. Finally, we predict that future work in this field will involve more investigations into epigenetic changes, experiments using new models of hormonal dysregulation in developing human prostate tissue, and continued delineation of the roles of the different ER subtypes, as well as their downstream signaling pathways that may serve as therapeutic targets.

Early iron deficiency has brain and behavior effects consistent with dopaminergic dysfunction

To honor the late John Beard's many contributions regarding iron and dopamine biology, this review focuses on recent human studies that test specific hypotheses about effects of early iron deficiency on dopamine system functioning. Short- and long-term alterations associated with iron deficiency in infancy can be related to major dopamine pathways (mesocortical, mesolimbic, nigrostriatal, tuberohypophyseal). Children and young adults who had iron deficiency anemia in infancy show poorer inhibitory control and executive functioning as assessed by neurocognitive tasks where pharmacologic and neuroimaging studies implicate frontal-striatal circuits and the mesocortical dopamine pathway. Alterations in the mesolimbic pathway, where dopamine plays a major role in behavioral activation and inhibition, positive affect, and inherent reward, may help explain altered social-emotional behavior in iron-deficient infants, specifically wariness and hesitance, lack of positive affect, diminished social engagement, etc. Poorer motor sequencing and bimanual coordination and lower spontaneous eye blink rate in iron-deficient anemic infants are consistent with impaired function in the nigrostriatal pathway. Short- and long-term changes in serum prolactin point to dopamine dysfunction in the tuberohypophyseal pathway. These hypothesis-driven findings support the adverse effects of early iron deficiency on dopamine biology. Iron deficiency also has other effects, specifically on other neurotransmitters, myelination, dendritogenesis, neurometabolism in hippocampus and striatum, gene and protein profiles, and associated behaviors. The persistence of poorer cognitive, motor, affective, and sensory system functioning highlights the need to prevent iron deficiency in infancy and to find interventions that lessen the long-term effects of this widespread nutrient disorder.

Hyperprolactinemia associated with psychotropics--a review

INTRODUCTION

Different classes of psychotropics can cause hyperprolactinemia to varying degrees. Among antipsychotics, typical agents and risperidone are the most frequent and significant offenders. In this review we discuss the pathophysiology, offending medications, assessment and management of hyperprolactinemia.

METHODS

We did a literature review between 1976 and 2008 using PubMed, MEDLINE, PsychINFO and Cochrane database. Search terms used were prolactin, hyperprolactinemia, psychotropics, antipsychotics, typical antipsychotics, atypical antipsychotics, antidepressants and SSRIs.

RESULTS

Prolactin elevation is more common with antipsychotics than with other classes of drugs. Typical antipsychotics are more prone to cause hyperprolactinemia than atypical agents. Management options include discontinuation of offending medication, switching to another psychotropic, supplementing concurrent hormonal deficiencies and adding a dopamine agonist or aripiprazole.

CONCLUSION

Clinicians need to be alert about the potential for hyperprolactinemia and its manifestations with these medications. Prolactin levels need to be monitored and other causes of hyperprolactinemia ruled out in suspected cases.

Medical causes and consequences of hyperprolactinaemia. A context for psychiatrists

Hyperprolactinaemia is the commonest endocrine disorder of the hypothalamic-pituitary axis and can lead to both short-term sexual dysfunction and galactorrhoea, and long-term loss of bone mineral density. Prolactin is secreted from the anterior pituitary gland under the influence of dopamine, which exerts a tonic inhibitory effect on prolactin secretion. Physiological regulators of prolactin secretion include many different types of 'stress' and sleep. Disruption of the normal control of prolactin secretion results in hyperprolactinaemia from pathological and pharmacological causes. The administration of antipsychotic medication is responsible for the high prevalence of hyperprolactinaemia in people with severe mental illness. Physiological hyperprolactinaemia, such as pregnancy and lactation, should be distinguished from pathological causes to prevent unnecessary investigation and treatment. The causes, consequences and management of hyperprolactinaemia are discussed in this article.

Iron deficiency in infancy predicts altered serum prolactin response 10 years later

Serum prolactin may reflect CNS dopaminergic function. Because iron deficiency (ID) alters brain dopamine in rats, serum prolactin levels were previously investigated in infants with varied iron status. High serum prolactin levels correlated with behaviors typical of chronic ID. The objective of this study was to determine the effect of infant iron status on serum prolactin levels after a stressor in early adolescence. One hundred fifty-nine of 191 children enrolled in infancy (chronic ID, n = 46; good iron comparison group, n = 113) had serum prolactin measurements after catheter placement at 11-14 y of age. Serum prolactin levels were compared by sex, pubertal status and infant iron status and the pattern of change over time was compared by infant iron status controlling for pubertal stage and background factors. Males and less mature adolescents had lower serum prolactin concentrations than females and more mature adolescents. Controlling for these factors, the serum prolactin response pattern differed significantly by infant iron status. Serum prolactin declined earlier for the chronic ID group. In conclusion, an altered serum prolactin response pattern was observed 10 y after chronic ID in infancy and may suggest a long-lasting effect of ID on the regulation of prolactin.

Short-term effects of alcohol consumption on the hormonal milieu and mood states in nulliparous women

The present study was designed to determine the short-term effects of alcohol consumption on hormonal responses and mood states in nulliparous women who have regular menstrual cycles. To this aim, we conducted a within-subjects design study in which eight women consumed a 0.4-g/kg dose of alcohol in orange juice during one test session (alcohol condition) and an equal volume of orange juice (control condition) during the other. Changes in plasma prolactin, oxytocin and cortisol levels, blood alcohol concentrations (BACs), and mood states were compared. BAC peaked at approximately 36.7+5.4 min after the consumption of the alcoholic beverage and decreased thereafter. Alcohol consumption significantly increased the area under the concentration-time curve (AUC) of prolactin (P<.01) and decreased the oxytocin AUC (P=.04) when compared to the control condition. Cortisol AUCs were not different across the two experimental conditions. Similar to that previously observed in lactating women, changes in prolactin and oxytocin paralleled changes in feelings of drunkenness. The magnitude and persistence of the alcohol-induced hormonal changes in nulliparous women were significantly less pronounced than those observed in lactating women, further highlighting the dynamics of the system under study during lactation.

From galactorrhea to osteopenia: rethinking serotonin-prolactin interactions

The widespread use of the selective serotonin reuptake inhibitors (SSRIs) has been accompanied by numerous reports describing a potential association with hyperprolactinemia. Antipsychotics are commonly known to elevate serum prolactin (PRL) through blockade of dopamine receptors in the pituitary. However, there is little awareness of the mechanisms by which SSRIs stimulate PRL release. Hyperprolactinemia may result in overt symptoms such as galactorrhea, which may be accompanied by impaired fertility. Long-term clinical sequelae include decreased bone density and the possibility of an increased risk of breast cancer. Through literature review, we explore the possible pathways involved in serotonin-induced PRL release. While the classic mechanism of antipsychotic-induced hyperprolactinemia directly involves dopamine cells in the tuberoinfundibular pathway, SSRIs may act on this system indirectly through GABAergic neurons. Alternate pathways involve serotonin stimulation of vasoactive intestinal peptide (VIP) and oxytocin (OT) release. We conclude with a comprehensive review of clinical sequelae associated with hyperprolactinemia, and the potential role of SSRIs in this phenomenon.

Hormones and breathing

A number of hormones, including hypothalamic neuropeptides acting as neurotransmitters and neuromodulators in the CNS, are involved in the physiologic regulation of breathing and participate in adjustment of breathing in disease. In addition to central effects, some hormones also control breathing at peripheral chemoreceptors or have local effects on the lungs and airways. Estrogen and progesterone seem to protect from sleep-disordered breathing, whereas testosterone may predispose to it. Progesterone and thyroxine have long been known to stimulate respiration. More recently, several hormones such as corticotropin-releasing hormone and leptin have been suggested to act as respiratory stimulants. Somatostatin, dopamine, and neuropeptide Y have a depressing effect on breathing. Animal models and experimental human studies suggest that also many other hormones may be involved in respiratory control.

Circadian aspects in the pathophysiology of the restless legs syndrome

Several pieces of evidence suggest that a dopaminergic dysfunction might play a key role in the pathophysiology of restless legs syndrome (RLS), including the therapeutic effects of dopaminergic drugs and the results of several positron emission tomography and single photon emission computed tomography studies. However, RLS symptoms display a distinct circadian pattern, with an increase of both sensorial and motor symptoms in the evening and at night. Although the latter could also be caused by homeostatic mechanisms such as a linkage to the previous amount of wakefulness, several studies performed over the last few years under semiconstant, routine conditions have suggested the existence of a 'true' circadian mechanism modulating the severity of RLS symptoms across the day-night cycle. Thus, both periodic leg movements of sleep and restlessness show a maximal severity in timely coincidence with the falling phase of the core temperature circadian cycle. The present article reviews the evidence showing circadian oscillation of dopaminergic function and postulates that the amplitude of circadian rhythm of dopaminergic function is increased in RLS, with a hypofunction at night.

Reference ranges for serum concentrations of lutropin (LH), follitropin (FSH), estradiol (E2), prolactin, progesterone, sex hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), cortisol and ferritin in neonates, children and young adults

The aim of this study was to establish reference ranges for children (neonates to young adults), for serum lutropin (LH), follitropin (FSH), estradiol (E2), progesterone, prolactin, sex hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), cortisol and ferritin, using the nonisotopic, automated chemiluminescence immunoassay system, Immulite (DPC). Serum samples from 762 children (369 female; age 1 day to 19 years) were examined. Of these, 381 were classified as pubertal. Due to non-normal distribution, the 2.5th, 50th and 97.5th percentiles (central 95% interval) were calculated for each group. Statistical differences between the reference ranges were analyzed with respect to age, sex and the stage of sexual maturation. The median concentrations of E2, prolactin, progesterone, DHEAS, cortisol and ferritin were higher during the first 2 weeks post-partum than thereafter. The largest difference was seen with prolactin, which showed up to 27-fold higher values during this period. In contrast, before the onset of puberty, hardly any sex difference was observed and all analyte concentrations remained relatively constant, apart from SHBG which increased steadily after the neonatal period. The increase of gonadal activity in females with the onset of sexual maturation included an increase in LH and FSH, which was accompanied by a strong increase in E2, progesterone and prolactin. Cortisol increased to a lesser extent during puberty. In males, the increase in the median concentrations of the hormones was smaller, except for DHEAS. The concentration of ferritin was high in the neonatal period but did not change during sexual maturation. Our findings agree with earlier studies. The calculated reference intervals can be used to assess the development of children, particularly for measurements performed by the Immulite and Immulite 2000 chemiluminescence assay systems.

Stress-induced hormonal and mood responses in scuba divers

The majority of injuries in scuba-divers are attributable to inappropriate behavior under stressful diving conditions, predominantly involving panic reactions emerging from elevated levels of anxiety. Divers with an elevated level of anxiety and poor coping are at higher risk of developing panic reactions than those possessing more adequate stress-coping-mechanisms. In the comparison of two extreme groups of seven divers each with opposite stress coping strategies, prolactin was found to be a hormonal marker with a significant increase in the sub-group of the stress-controllers. This hormonal response was observed in a recreational and a stressful dive, and in the latter with a more distinct elevation. Along with the self-reported emotional conditions under immersion, these data suggest that an increased prolactin level reflects a state of elevated physical and mental activation and vigilance. Facing a stressful situation subjects with more emotional concern and the tendency to surrender react by "blunted responses" and show significantly lower elevations of the prolactin levels in contrast to subjects with the very opposite psychological features. The other observed somatic parameters (epinephrine, norepinephrine) showed significant increases during and after dives (with the exception of saliva cortisol), however without any significant group difference.

Absence of prolactin gene expression in colorectal cancer

AIMS

Previous studies documenting hyperprolactinaemia in patients with colorectal cancer have suggested that the tumour is the source of hormone production. The aim of this study was to determine the frequency of hyperprolactinaemia in patients with colorectal cancer before, during, and after surgery, and also to determine whether prolactin is produced by these tumours.

METHODS

Serum prolactin concentrations were measured in 20 patients with colorectal cancer before, during, and after surgical resection of their tumours. Samples taken during surgery included peripheral venous blood and blood taken from the main veins draining the tumour. To determine whether the tumour was responsible for the production of prolactin in these patients, paraffin wax embedded sections of tumour specimens were subjected to immunohistochemistry and western blotting using a monoclonal antibody to prolactin.

RESULTS

Five patients (three women, two men) had preoperative prolactin concentrations above the normal reference range, although this increase was of clinical importance in only two. After surgical resection of their tumours, prolactin concentrations remained high in both patients. All 20 patients had greatly raised prolactin values at the time of surgery, irrespective of whether this was measured in peripheral blood or in blood taken from veins draining the tumour. All 20 colorectal cancer tissue samples, including those with raised preoperative and/or postoperative prolactin concentrations, were negative for prolactin staining. Frozen tissue was also available in four cases. The absence of prolactin gene expression in these four tumours was confirmed both by repeat immunohistochemistry and by western blotting. A further 50 colorectal cancer cases examined by immunohistochemistry alone were also unreactive for prolactin.

CONCLUSIONS

The results of this study suggest that serum prolactin concentrations may occasionally be raised in colorectal cancer patients, but that the tumour is not the source of hormone production.

Blood oxygen partial pressure affects plasma prolactin concentration in humans

Responses of plasma prolactin (PRL) concentration to acute and repeated changes in blood oxygen partial pressure (PO2a) at rest were investigated in two studies (A; B), with special reference to possible effects mediated via serotonin (5-HT) synthesis. In A, nine male subjects inhaled for 105 min gas containing different oxygen fractions for 6 days. Gas concentrations consisted of 14% (A14), 21 % (A21), 40% (A40), 60% (A60) and 80% (A80) O2 mixed with N2 as well as 100% O2 (A100). Venous and capillary blood samples were drawn before and every 15 min during gas inhalation for analysis of plasma PRL and PO2a. In B, two groups of subjects (B I; B II) were exposed to 30 min day(-1) of gas inhalation over 14 consecutive days. Gas concentration consisted for B I of 14% O2/86% N2 and for B II of 100% O2. During pre- and post-examination a baseline blood sample was drawn, followed by a neuroendocrine test of serotonergic function using a partial 5-HT1A receptor agonist (60 mg of buspirone hydrochloride). In A, each increase of inhaled oxygen fraction also resulted in higher blood POb2a. In A14, A21 and A40, plasma PRL concentrations did not change from basal level. Increases in plasma PRL concentration were found in A60 after 30 min as well as in A80 and A100 after 15 min. A higher blood PO2a induced a higher plasma PRL secretion but also an earlier decline from peak plasma PRL value despite continued inhalation of the respective oxygen concentration. During post-examination in B, basal plasma PRL concentrations were increased in B I and decreased in B II. Plasma PRL response to stimulation challenge was not affected by treatments. Thus, chronic adaptations of basal plasma PRL concentrations to decreased/increased blood PO2a were not related to up/down-regulation, respectively, of central serotonergic receptor function.

Prolactin response to D-fenfluramine challenge test as a predictor of treatment response to haloperidol in acute schizophrenia

D-fenfluramine has been identified as a highly selective serotonin (5-HT) releaser and re-uptake inhibitor. The objective of our study was to investigate prolactin response to D-fenfluramine challenge in non-medicated, first episode schizophrenics. We hypothesized that 5-HT reactivity can predict a response to the neuroleptic treatment. Twenty-three inpatients, 11 males and 12 females, at the Prague Psychiatric Center participated in the study. Inclusion criteria were: ICD-10 diagnosis of schizophrenia, first episode or duration of illness shorter than 36 months. D-fenfluramine challenge test was performed before 4 weeks of the haloperidol treatment. During the test, prolactin plasma levels were measured. The Brief Psychiatric Rating Scale (BPRS) was administered before and after the treatment. A statistically significant negative correlation was found between prolactin response to the D-fenfluramine challenge and improvement of psychopathology measured by the change in total BPRS score (p = 0.0004), in positive (p = 0.0403), negative (p = 0.0267), and anxiety-depression symptoms of BPRS (p = 0.0014). Our data support the original hypothesis that there is a relationship between 5-HT system activity and treatment response. The higher responsiveness of the 5-HT system in first episode, non-medicated schizophrenics, was associated with a poorer treatment response to haloperidol, an antidopaminergic neuroleptic.

Persistent endocrine stress response in patients undergoing cardiac surgery

To investigate the endocrine stress response in patients undergoing major surgery with general anesthesia using a balanced technique with sufentanil, isoflurane and midazolam up to the second postoperative day, blood levels of cortisol, epinephrine, norepinephrine, prolactin and growth hormone were determined in 68 males for elective coronary artery bypass grafting (CABG) surgery. Intraoperatively, during extracorporeal circulation none of the measured parameters were significantly increased compared to preoperative values. The endocrine response of patients with perioperative epinephrine medication (n = 32) was not significant different to patients that did not receive exogenous epinephrine (n = 36). On the evening of the day of surgery, levels of cortisol (3 fold), epinephrine (4.7 fold), norepinephrine (1.7 fold) and growth hormone (16.5 fold) were significantly increased. Compared to preoperative values levels of cortisol (3.3 fold), growth hormone (5.5 fold) and norepinephrine (1.8 fold) remained elevated up to the evening of the second postoperative day. In conclusion, the endocrine stress response in patients undergoing CABG-surgery under general anesthesia with sufentanil, midazolam, isoflurane is intraoperatively prevented by anesthesia. Although hemodilution or hormone degradation might be responsible for the lack of an increase in endocrine parameters during CPB, this study indicates that a balanced technique with isoflurane, sufentanil and midazolam is more effective in blocking the endocrine stress response than previously described anesthetic techniques. In the early postoperative period, a sharp increase in cortisol, epinephrine, norepinephrine and growth hormone occurred suggesting that the predominant endocrine stress response begins in the intensive care unit with end of anesthesia. The postoperative elevated levels of cortisol, growth hormone and norepinephrine indicate a persisting stress-response for more than two days after surgical trauma.

Effect of O2 availability on neuroendocrine variables at rest and during exercise: O2 breathing increases plasma prolactin

Neuroendrocrine and substrate responses were investigated in eight male athletes during inhalation of either 100% O2 (HE), 14% O2 (HO) or normoxio gas (NO) before, during and after 60 min of cycle ergometry at the same absolute work rate. Concentrations of prolactin (PRL), growth hormone (GH), testosterone (T), adrenocorticotropic hormone (ACTH), cortisol (COR), adrenalin (A), noradrenalin (NA), insulin (INS), ammonia (NH3), free fatty acids, serotonin (5-HT), total protein, branched-chain amino acids (BCAA) and free tryptophan (free TRP) were determined in venous blood and lactate concentration [LA-], partial pressure of oxygen (PO2), oxygen saturation (SO2), partial pressure of carbon dioxide and pH in capillary blood. The PO2 and SO2 were augmented in HE and decreased in HO (P < or = 0.01). In HO and NO no significant changes were found for any other parameter during 30 min of rest prior to exercise. In HE, PRL increased by about 400% during this time, while NA declined (P < or = 0.01). Heart rate (HR) and [LA-] were higher during exercise in HO (P < or = 0.01). In all trials, NH3, NA, A, T, GH and ACTH increased during exercise (P < or = 0.01), while BCAA and INS declined. In comparison to NO and HE, increases of NA, A, GH, COR and ACTH were higher in HO (P < or = 0.01). The PRL in NO and COR in NO and HE did not change significantly. In HE, after the initial increase at rest, PRL declined during exercise but remained higher than in HO. Higher values for NA, A, GH, COR and ACTH in HO were likely to have reflected an augmented relative exercise intensity. Our results showed that PRL but no other hormone increased during acute exposure to hyperoxia. This PRL release was independent of exercise stress and greater than PRL augmentation during hypoxia, which was related to a higher relative exercise intensity as indicated by [LA-] and HR. Responses of plasma NH3, BCAA, free TRP and 5-HT could not explain PRL augmentation induced by the increment in blood SO2 during hyperoxia.

Serum prolactin levels and behavior in infants

This study examined the relationship between serum prolactin levels and behavior in infants and toddlers who experienced two potentially stressful experiences (developmental testing and venipuncture). Serum prolactin levels showed considerable consistency over a 3-month period (r = 0.64 between study entry and three months, p < 0.001, n = 50). There was also stability in having either a normal or a high value (> or = 25 ng/ml). Among children who had a normal value on initial testing, 97% also has a normal value after 3 months; 55% of those with initial high values continued to have high values (chi 2 = 19.26, p < 0.001). Children with high serum prolactin levels were more likely to be rated as unusually hesitant and unhappy during developmental testing. Overall, 53% of the children with serum prolactin levels > or = 25 ng/ml were considered abnormal in affect, compared to 20% of those with lower serum prolactin values (total n = 138, chi 2 = 13.56, p < 0.001). These results suggest that, even in early life, serum prolactin levels may reflect characteristic individual behavioral and neuroendocrine responses to stress.

The influence of calcium infusion on serum prolactin in hyperprolactinemic women

This study investigated the influence of calcium on serum prolactin (PRL) in hyperprolactinemic and healthy women. Previous studies have shown an inhibitory effect of Ca2+ on serum PRL, related to the degree of hypercalcemia. Serum PRL levels were measured by immunoradiometric assay (IRMA) in subjects before and one hour after 1375 mg Ca2+ injection. Serum PRL level was significantly decreased by calcium injection in hyperprolactinemic women (89.2 +/- 29.1 and 63.3 +/- 35.8 ng/ml; p < 0.01) while it was not significant (p > 0.05) in women with normal PRL levels (12.6 +/- 5.1 ng/ml and 11.3 +/- 4.0 ng/ml). These results indicate that acute alterations in serum calcium levels affect PRL secretion in hyperprolactinemic women.

Control of prolactin-secreting macroadenomas with parenteral, long-acting bromocriptine in 30 patients treated for up to 3 years

OBJECTIVE

We investigated the effect of intramuscular injections of long-acting bromocriptine in patients with macroadenomas.

STUDY DESIGN AND PATIENTS

Thirty patients with PRL-secreting pituitary macroadenomas were treated with repeated 4-weekly intramuscular injections of 50 or 100 mg of a long-acting, repeatable bromocriptine formulation for six to 37 injections, amounting to a total of 473 injections. Twenty patients received parenteral bromocriptine as primary therapy, ten had persisting hyperprolactinemia after previous therapies including pituitary surgery (n = 7), oral bromocriptine (7), and pituitary irradiation (2).

MEASUREMENTS

A PRL day profile was obtained and the patients' clinical status and history were documented, at intervals. Detailed clinical, laboratory, and radiological (pituitary nuclear magnetic resonance or computed tomography scan) evaluations were performed at baseline, after 1 injection and every 6th injection thereafter.

RESULTS

In all patients PRL was suppressed from a mean +/- SEM pretreatment level of 32,620 +/- 8680 to 4480 +/- 1140 mU/I on the third day after the first injection. In 12 patients PRL levels normalized (< 400 mU/I) with the first to fourth injection, in three additional patients PRL levels normalized after 8-15 months. In 19 patients PRL was suppressed to less than 1000 mU/l. In three patients PRL did not decrease to less than 50% of pretreatment; in two of them on oral bromocriptine prior to this study there had been a comparable low efficacy. Of 28 patients with macroadenomas (median height 22 mm) tumour shrinkage was evident in 15 by nuclear magnetic resonance or computed tomography scan 28 days after the first injection, and in three additional patients after 6 months. There was further regression in seven cases after 12, 18 or 24 injections. Adenoma size (mean +/- SEM) decreased to 66 +/- 7% of the pretreatment value. The 40 adverse events noted in 20 of 30 patients during 24 hours after the first injection were similar to known side-effects of oral bromocriptine, nausea and postural hypotension being the most frequent. With repeated injections, on average 0.6 adverse events were noted per injection (mostly mild asthenia). There were no local adverse reactions at the injection site.

CONCLUSION

We conclude that long-acting repeatable bromocriptine in patients with macroprolactinomas offers a safe and efficacious primary treatment that ensures compliance and gives long-term control. Adverse reactions are comparable to oral bromocriptine but subside with repeated injections.

Effects of central and peripheral type benzodiazepine ligands on thyrotropin and prolactin secretion

The cold-stimulated thyrotropin (TSH) levels in the rat were decreased by clonazepam (a central type benzodiazepine agonist), diazepam (a mixed agonist), FG 7142 (an inverse central type agonist) and Ro 5-4864 (a peripheral type agonist), clonazepam being the most potent and Ro 5-4864 the least active. Clonazepam and diazepam also decreased while FG 7142 increased prolactin (PRL) levels. Ro 5-4864 did not have any significant action. Clonazepam (1 and 5 mg/kg) and diazepam (15 mg/kg but not 25 mg/kg) decreased even the TRH-induced PRL levels. Only Ro 5-4864 (25 mg/kg) decreased TRH-induced TSH secretion but not significantly. The actions of central type compounds were antagonized by flumazenil but not by PK 11195. The weak effects of Ro 5-4864 were not antagonized by either antagonists. While the peripheral type benzodiazepine agonist only weakly affected the secretion of anterior pituitary hormones, the central type inhibition of TSH appears to be mediated through the hypothalamic TRH and that of PRL rather through the anterior pituitary gland. The sedating (or agitating in case of FG 7142) effect of high doses of benzodiazepine ligands may contribute to the changes in TSH and PRL levels.