Immunomodulating Effects Depend on Prolactin Levels in Patients with Hyperprolactinemia.

Prolactin is known to have immune modulatory effects acting through the prolactin receptor, which is present on a variety of immune cells. Certain chemokines contribute to form the type of T helper (Th) preponderance in the immune response. The objective of this work was to assess if hyperprolactinemia not related to pregnancy is associated with changes in circulating levels of chemokines and other immunological markers. In this cross sectional study, 35 patients with hyperprolactinemia (5 men), and 102 healthy blood donors (19 men) were included. Serum levels of Th1- Th2- and Th17-associated chemokines, C-reactive protein, immunoglobulins, and the B cell attracting chemokine CXCL13 were assessed. The hyperprolactinemic group had significantly higher levels of Th2 associated CCL22 (p=0.022), Th17 associated CXCL1 (p=0.001), B cell attracting CXCL13 (p=0.003), and C-reactive protein (p<0.001) compared to controls, and these proteins were also positively correlated with prolactin levels. While differences in CCL22, CXCL1, CXCL13, and C-reactive protein were present in patients with low or moderate hyperprolactinemia, no differences were observed at high (>3600 mU/l) prolactin levels. To evaluate a possible dose-associated response to prolactin, an in vitro model was used, showing prolactin-induced increase in T-helper cell activation at moderate levels, while activation decreased at higher levels. Hyperprolactinemia seems to have several immunomodulatory effects and was associated with increased levels of chemokines associated with Th2 and Th17 responses and B cell attraction. However, patients with greatly increased prolactin had normal levels of chemokines, and in vitro, high levels of prolactin decreased T-helper cell activation.

Evaluation of autoantibodies and immunoglobulin G subclasses in women with suspected macroprolactinemia.

BACKGROUND: Macroprolactin mostly composed of an immunoglobulin G (IgG) and a monomeric prolactin (PRL) represents the major circulating PRL form in the patients with macroprolactinemia that are usually asymptomatic and may not require treatment. In this study, we aimed to evaluate the prevalence of antithyroid and antinuclear antibodies, as well as the IgG subclass distributions in the patients suspected for macroprolactinemia. METHODS: From January to July in 2018, totally 317 patients with elevated PRL were subjected to the polyethylene glycol (PEG) precipitation assay. The patients with recovery rates of ≤60% were subjected for IgG subclass determination and autoantibody testing including thyroid peroxidase antibody (aTPO), antithyroglobulin antibody (aTG), and antinuclear antibodies (ANA). RESULTS: The higher the post-PEG PRL recovery rates, the less typical hyperprolactinemia symptoms and the higher prevalence of autoantibodies were observed. The IgG1 and IgG3 were the predominant subclasses in the PRL-IgG complexes according to the immunoprecipitation experiments. CONCLUSION: The patients with post-PEG PRL recovery rates of <40% and 40%-60% were likely to represent two distinct populations of different clinical presentations. The prevalence of autoantibodies and IgG subclasses distribution suggested their pathogenic significance in the development of macroprolactinemia.

Short-Term Hyperprolactinemia Reduces the Expression of Purinergic P2X7 Receptors during Allergic Inflammatory Response of the Lungs.

PURPOSE: We have previously shown that domperidone-induced short-term hyperprolactinemia reduces the lung's allergic inflammatory response in an ovalbumin antigenic challenge model. Since purinergic receptor P2X7R activity leads to proinflammatory cytokine release and is possibly related to the pathogenesis of allergic respiratory conditions, the present study was designed to investigate a possible involvement of purinergic and prolactin receptors in this phenomenon. METHODS: To induce hyperprolactinemia, domperidone was injected intraperitoneally in rats at a dose of 5.1 mg × kg-1 per day for 5 days. P2X7 expression was evaluated by lung immunohistochemistry while prolactin receptor expression in bronchoalveolar lavage leukocytes was analyzed through flow cytometry. RESULTS: Previous reports demonstrated that rats subjected to short-term hyperprolactinemia exhibited a decrease in leukocyte counts in bronchoalveolar lavage, especially granulocytes. Here, it is revealed that hyperprolactinemia promotes an increased expression of prolactin receptors in granulocytes. Also, increased expression of purinergic P2X7R observed in allergic animals was significantly reduced by hyperprolactinemia. CONCLUSIONS: Both purinergic and prolactin receptor expression changes occur during the anti-asthmatic effect of hyperprolactinemia.

Urine oligosaccharide pattern in patients with hyperprolactinaemia.

Free milk-type oligosaccharides are produced during pregnancy and lactation and may have an impact on several cells in the immune system. Our aim was to investigate if patients with isolated hyperprolactinaemia, not related to pregnancy, also have increased synthesis and urinary excretion of milk-type oligosaccharides and to compare the excretion pattern with that found during pregnancy. Urine samples were collected as morning sample from 18 patients with hyperprolactinaemia, 13 healthy controls with normal prolactin levels and four pregnant women. After purification, lactose and free oligosaccharides were analysed and quantified by high-performance anion-exchange chromatography with pulsed amperometric detection. The identity of peaks was confirmed by exoglycosidase treatment and comparison with oligosaccharide standards. Prolactin was measured in serum collected between 09 and 11 a.m. by a standardized immunochemical method. Patients with hyperprolactinaemia had higher urinary excretion of lactose than normoprolactinemic controls and urinary lactose correlated positively to prolactin levels (r = 0.51, p < 0.05). Increased levels of the fucosylated oligosaccharides 2-fucosyl lactose and lacto-di-fucotetraose were found in urine from three and two patients, respectively. The acidic oligosaccharide 3-sialyl lactose was found in high amount in urine from two patients with prolactin of >10,000 mU/l. However, pregnant women in their third trimester had the highest concentration of all these oligosaccharides and excretion increased during pregnancy. This study is first to show that both lactose and certain fucosylated and sialylated milk-type oligosaccharides are increased in some patients with hyperprolactinaemia. It remains to elucidate the functional importance of these findings.

Serum macroprolactin levels in pregnancy and association with thyroid autoimmunity.

BACGROUND: To assess the contribution of macroprolactin to high serum prolactin levels and their association with thyroid status and thyroid autoimmunity during pregnancy. METHODS: 138 pregnant women who suspected of having thyroid dysfunction were studied and divided into three groups according to the thyroid status; group 1; euthyroidism (n 40), group 2; hypothyroidism (n 54), and group 3; hyperthyroid (n 44). Polyethylene glycol (PEG) precipitation method was used for detection of macroprolactin. A percentage recovery of 40 % or less is considered as macroprolactinemia. If macroprolactin was negative, the percentage of monomeric prolactin recovery (monoPRL %) after PEG precipitation was used for comparison between the groups. RESULTS: Macroprolactinemia was found in two patients (1.4 %) one from hypothyroid and other from euthyroid group. Basal prolactin levels in these patients were 400 and 403 ng/mL respectively. Referring to all patients, there was no correlation between PRL, macroPRL or monoPRL % with thyroid hormone status and also with the serum levels of thyroid antibodies (p > 0.05). A positive correlation was observed between the serum levels of PRL with TSH (p = 0.014 and r = 0.219), while a negative correlation was found with FT4 (p = 0.011 and r = -0.227). CONCLUSIONS: Despite the fact that serum prolactin levels were found to be high during pregnancy, the contribution of macroprolactin was found to be insignificant in our study. Unlike other auto immune diseases, we could not find any relationship between thyroid autoimmunity and PRL, macroPRL or monoPRL %. These results confirmed that measured prolactin was quite homogeneous during pregnancy.

Prolactin rescues and primes autoreactive B cells directly and indirectly through dendritic cells in B6.Sle3 mice.

The lupus susceptibility interval Sle3/5 confers responsiveness to prolactin in C57BL/6 (B6) mice and hyperprolactinaemia induces a lupus-like phenotype in B6.Sel3/5 mice. In this study, the immunostimulatory effects of prolactin in B6 mice containing the Sle3 portion of the Sel3/5 interval (B6.Sle3 mice) were dissected. Because of the Sle3 interval's involvement in activation of myeloid cells, the effect of dendritic cells (DCs) from prolactin-treated B6.Sle3 mice on the phenotype of B6 mice was also evaluated. B cells from prolactin-treated B6 and B6.Sle3 mice and from B6 recipients of prolactin-modulated DCs from B6.Sle3 mice were tested for DNA-reactivity and resistance to B cell receptor (BCR)-mediated apoptosis. The expression of co-stimulatory molecules on lymphocytes and myeloid cells was also evaluated. In prolactin-treated B6.Sle3 mice, transitional type 2 B cells increased while type 1 B cells decreased as a consequence of prolactin-induced resistance to BCR-mediated apoptosis leading to the survival of DNA-reactive B cells. Follicular B cells from prolactin-treated mice expressed increased levels of CD40, B7·2 and IA(b), and DCs and monocytes had higher levels of CD44 and B7·2 than placebo-treated mice. Adoptive transfer of DCs from prolactin-treated B6.Sle3 mice to B6 recipients demonstrated the intrinsic ability of prolactin-modulated DCs to induce a development of lupus-like characteristics in B6 mice. Based on these results, prolactin accelerates the breakdown of immune tolerance in B6.Sle3 mice by promoting the survival, maturation and activation of autoreactive B cells, DCs and macrophages.

Prolactin promotes normal liver growth, survival, and regeneration in rodents: effects on hepatic IL-6, suppressor of cytokine signaling-3, and angiogenesis.

Prolactin (PRL) is a potent liver mitogen and proangiogenic hormone. Here, we used hyperprolactinemic rats and PRL receptor-null mice (PRLR(-/-)) to study the effect of PRL on liver growth and angiogenesis before and after partial hepatectomy (PH). Liver-to-body weight ratio (LBW), hepatocyte and sinusoidal endothelial cell (SEC) proliferation, and hepatic expression of VEGF were measured before and after PH in hyperprolactinemic rats, generated by placing two anterior pituitary glands (AP) under the kidney capsule. Also, LBW and hepatic expression of IL-6, as well as suppressor of cytokine signaling-3 (SOCS-3), were evaluated in wild-type and PRLR(-/-) mice before and after PH. Hyperprolactinemia increased the LBW, the proliferation of hepatocytes and SECs, and VEGF hepatic expression. Also, liver regeneration was increased in AP-grafted rats and was accompanied by elevated hepatocyte and SEC proliferation, and VEGF expression compared with nongrafted controls. Lowering circulating PRL levels with CB-154, an inhibitor of AP PRL secretion, prevented AP-induced stimulation of liver growth. Relative to wild-type animals, PRLR(-/-) mice had smaller livers, and soon after PH, they displayed an approximately twofold increased mortality and elevated and reduced hepatic IL-6 and SOCS-3 expression, respectively. However, liver regeneration was improved in surviving PRLR(-/-) mice. PRL stimulates normal liver growth, promotes survival, and regulates liver regeneration by mechanisms that may include hepatic downregulation of IL-6 and upregulation of SOCS-3, increased hepatocyte proliferation, and angiogenesis. PRL contributes to physiological liver growth and has potential clinical utility for ensuring survival and regulating liver mass in diseases, injuries, or surgery of the liver.

Prolactin levels correlate with abnormal B cell maturation in MRL and MRL/lpr mouse models of systemic lupus erythematosus-like disease.

Prolactin (PRL) plays an important role in modulating the immune response. In B cells, PRL enhances antibody production, including antibodies with self-specificity. In this study, our aims were to determine the level of PRL receptor expression during bone-marrow B-cell development and to assess whether the presence of high PRL serum concentrations influences absolute numbers of developing populations and disease outcome in lupus-prone murine models. We observed that the PRL-receptor is expressed in early bone-marrow B-cell; the expression in lupus-prone mice, which had the highest level of expression in pro-B cells and immature cells, differed from that in wild-type mice. These expression levels did not significantly change in response to hyperprolactinemia; however, populations of pro-B and immature cells from lupus-prone strains showed a decrease in the absolute numbers of cells with high PRL-receptor expression in response to PRL. Because immature self-reactive B cells are constantly being eliminated, we assessed the expression of survival factor BIRC5, which is more highly expressed in both pro-B and immature B-cells in response to PRL and correlates with the onset of disease. These results identify an important role of PRL in the early stages of the B-cell maturation process: PRL may promote the survival of self-reactive clones.

Increased levels of prolactin receptor expression correlate with the early onset of lupus symptoms and increased numbers of transitional-1 B cells after prolactin treatment.

BACKGROUND: Prolactin is secreted from the pituitary gland and other organs, as well as by cells such as lymphocytes. Prolactin has an immunostimulatory effect and is associated with autoimmune diseases that are characterised by abnormal B cell activation, such as systemic lupus erythematosus (SLE). Our aim was to determine if different splenic B cell subsets express the prolactin receptor and if the presence of prolactin influences these B cell subsets and correlates with development of lupus. RESULTS: Using real-time PCR and flow cytometry, we found that different subsets of immature (transitional) and mature (follicular, marginal zone) B cells express different levels of the prolactin receptor and are differentially affected by hyperprolactinaemia. We found that transitional B cells express the prolactin receptor at higher levels compared to mature B cells in C57BL/6 mice and the lupus-prone MRL/lpr and MRL mouse strains. Transitional-1 (T1) B cells showed a higher level of prolactin receptor expression in both MRL/lpr and MRL mice compared to C57BL/6 mice. Hyperprolactinaemia was induced using metoclopramide, which resulted in the development of early symptoms of SLE. We found that T1 B cells are the main targets of prolactin and that prolactin augments the absolute number of T1 B cells, which reflects the finding that this B cell subpopulation expresses the highest level of the prolactin receptor. CONCLUSIONS: We found that all B cell subsets express the prolactin receptor but that transitional B cells showed the highest prolactin receptor expression levels. Hyperprolactinaemia in mice susceptible to lupus accelerated the disease and increased the absolute numbers of T1 and T3 B cells but not of mature B cells, suggesting a primary effect of prolactin on the early stages of B cell maturation in the spleen and a role of prolactin in B cell differentiation, contributing to SLE onset.

Inhibitory effect of prolactin on Toxoplasma proliferation in peripheral blood mononuclear cells from patients with hyperprolactinemia.

Despite many years of studies on the mechanisms of immunological defence responses induced in host organisms by Toxoplasma, no satisfactory immunoprophylaxis or chemotherapy have yet been established for humans. Thus, alternative methods to prevent toxoplasmosis and to enhance the efficacy of currently used antitoxoplasmic drugs are under evaluation. In this work, we strove to determine the influence of human prolactin (endogenous present in serum--sPRL and recombinant--rhPRL) on the course of Toxoplasma infection of peripheral blood mononuclear cells (PBMC) originating from female hyperprolactinemia patients. This study revealed that exogenous rhPRL as well as autologous sPRL from inactivated sera significantly restricted intracellular growth of Toxoplasma in PBMC cultures. Moreover, analysis of IL-10 production by PBMC infected with Toxoplasma and cultured in the presence of sPRL showed a positive correlation between sPRL concentration and the level of IL-10. The obtained results could indicate the possible protective action of PRL in a host organism infected with Toxoplasma and suggest that a significant increase in the serum PRL level, during pregnancy for instance, might significantly limit the risk of Toxoplasma spreading and could play an important role in natural protection against toxoplasmosis. The mechanism of inhibitory effect of PRL needs further detailed study.

Macroprolactinemia: diagnostic, clinical, and pathogenic significance.

Macroprolactinemia is characterized by a large molecular mass of PRL (macroprolactin) as the main molecular form of PRL in sera, the frequent elevation of serum PRL (hyperprolactinemia), and the lack of symptoms. Macroprolactin is largely a complex of PRL with immunoglobulin G (IgG), especially anti-PRL autoantibodies. The prevalence of macroprolactinemia is 10-25% in patients with hyperprolactinemia and 3.7% in general population. There is no gender difference and a long-term followup demonstrates that macroprolactinemia develops before middle age and is likely a chronic condition. Polyethylene-glycol- (PEG-) precipitation method is widely used for screening macroprolactinemia, and gel filtration chromatography, protein A/G column, and I125-PRL binding studies are performed to confirm and clarify its nature. The cross-reactivity of macroprolactin varies widely according to the immunoassay systems. The epitope on PRL molecule recognized by the autoantibodies is located close to the binding site for PRL receptors, which may explain that macroprolactin has a lower biological activity. Hyperprolactinemia frequently seen in macroprolactinemic patients is due to the delayed clearance of autoantibody-bound PRL. When rats are immunized with rat pituitary PRL, anti-PRL autoantibodies are produced and hyperprolactinemia develops, mimicking macroprolactinemia in humans. Screening of macroprolactinemia is important for the differential diagnosis of hyperprolactinemia to avoid unnecessary examinations and treatments.

Unfavorable effects of hyperprolactinemia in autoimmune endocrine disorders.

Prolactin is a hormone with a multidirectional proinflammatory action. It has an anti-apoptotic effect, enhances proliferative response to antigens and mitogens, as well as enhances the production of immunoglobulins and autoantibodies. Increased prolactin levels are commonly observed in various organ and multi-organ specific autoimmune diseases. In our article, we report a case of a woman who developed progression of autoimmune thyroid disorder and developed insufficiency of the zona glomerulosa when her prolactin levels were increased. A normalization of plasma prolactin levels by quinagolide and replacement of risperidone with aripiprazole improved her clinical condition. Our study suggests that, in some patients, hyperprolactinemia may predispose to the development and progression of autoimmune disorders of endocrine glands.

Dual effects of hyperprolactinemia on carrageenan-induced inflammatory paw edema in rats.

OBJECTIVES: The effects of short-term 5-day and long-term 30-day hyperprolactinemia induced by domperidone (1.7 mg/kg/day, s.c.) or ectopic pituitary graft on the acute inflammatory response induced by carrageenan were evaluated in male rats. Both models of hyperprolactinemia effectively increased serum prolactin (PRL) levels. METHODS: The volume in milliliters of inflammatory edema was measured by plethysmography 1, 2, 3, 4, 6, 8 and 24 h after carrageenan injection. The areas under the inflammatory time-response curves were compared. Additionally, the effects of hyperprolactinemia on body weight and serum corticosterone levels were evaluated. RESULTS: In both domperidone-treated and pituitary graft-implanted animals, short-term 5-day hyperprolactinemia increased the inflammatory response, while long-term 30-day hyperprolactinemia had anti-inflammatory effects. Body weight was not affected by either short- or long-term hyperprolactinemia. CONCLUSION: These results show that PRL has biphasic effects on the carrageenan-induced inflammatory response.

Distribution of Myeloid and Plasmacytoid Dendritic Cell Subpopulations in Peripheral Blood of Hyperprolactinemic Women.

Dendritic cells (DCs) play key roles in regulating the immune response using the specialized function of processing and presenting antigens. Prolactin (PRL), a hormone produced by the pituitary gland, participates in DC maturation and function. The present study was aimed to determine the frequencies of peripheral blood DC subpopulations of myeloid DC (MDC) and plasmacytoid DC (PDC) in hyperprolactinemic (HPRL) women compared to normal healthy volunteers. This study was conducted on 70 women, including 35 HPRL patients and 35 matched healthy controls, whose PRL serum levels were in the normal range (lower than 25 ng/mL). Serum thyroid-stimulating hormone (TSH) levels were measured in both groups as an indicator of normal thyroid function. The electrochemiluminescence immunoassay method was applied to measure the serum levels of TSH and PRL. The frequencies of MDC and PDC in the peripheral blood samples of both groups were determined by flow cytometry. The mean serum PRL levels in the HPRL patients and healthy individuals were 46.41±21.96 and 13.75±11.19, respectively (p<0.0001); however TSH levels in both groups were similar and within the normal range (0.4-4.5 mIU/mL) (p=0.2). The frequencies of both MDC and PDC subpopulations in the peripheral blood of HPRL patients were significantly lower than they were in the healthy controls. However, the ratio of MDCs/PDCs in HPRL patients was not significantly different between the two groups (p=0.8). Our study revealed that an increased level of serum PRL may lead to a reduction in the number of MDC and PDC subpopulations. These results could help clarify the complex relationship between the immune system and the neuroendocrine axis and may be of potential use in understanding the pathogenesis of endocrine and immune disorders.

Prolactin, metabolic and immune parameters in naïve subjects with a first episode of psychosis.

BACKGROUND: Prolactin (Prl) is a pleiotropic hormone initially described for its regulation of lactation in mammals but later associated with metabolic and immune homeostasis, stress, inflammatory response and human behavior. Its regulation through dopamine receptors highlights its importance in psychiatry mostly because hyperprolactinemia is a common secondary side effect of dopamine antagonists. Despite its undeciphered patho-physiological mechanisms, hyperprolactinemia in naïve psychosis patients has been widely described. Its consequences might underlie the increased morbidity and early mortality found in naïve subjects as described in the general population where prolactin values have been correlated with inflammatory, immune and metabolic parameters. METHODS: We aimed to evaluate the correlation between prolactin values and other biochemical parameters (C-reactive Protein-CrP, blood cell count, lipid and hepatic profile, fasting glucose) in a cohort of first episode psychosis naïve subjects (N = 491) stratified by sex. Regression analyses with confounders were performed to evaluate the association. FINDINGS: Prl displayed significant correlations with C-Reactive Protein (CrP), Low-Density Lipoprotein (LDL), Aspartate Transaminase (AST) for females and High-Density Lipoprotein (HDL) and eosinophil count for males. However, and despite previous specific sex correlations, significant associations were described for CrP, HDL, LDL, AST and ALT without sex interaction and despite confounders such as age, Body Mass Index or smoking status. CONCLUSIONS: Our results show a specific relation of Prl with immune and metabolic parameters describing a heterogeneous pattern. Our results suggest that prolactin might underlie the excess of morbidity and early mortality in naïve patients through a specific pathway.

Acute and chronic stress and the inflammatory response in hyperprolactinemic rats.

BACKGROUND/AIM: Prolactin (PRL), a hormone produced by the pituitary gland, has multiple physiological functions, including immunoregulation. PRL can also be secreted in response to stressful stimuli. During stress, PRL has been suggested to oppose the immunosuppressive effects of inflammatory mediators. Therefore, the aim of the present study was to analyze the effects of short- and long-term hyperprolactinemia on the inflammatory response in rats subjected to acute or chronic cold stress. METHODS: Inflammatory edema was induced by carrageenan in male rats, and hyperprolactinemia was induced by injections of the dopamine receptor antagonist domperidone. The volume of inflammatory edema was measured by plethysmography after carrageenan injection. Additionally, the effects of hyperprolactinemia on body weight and serum corticosterone levels were evaluated. RESULTS AND CONCLUSION: Five days of domperidone-induced hyperprolactinemia increased the volume of inflammatory edema. No differences in serum corticosterone levels were observed between groups. No significant differences were found among 30 days domperidone-induced hyperprolactinemic animals subjected to acute stress and the inflammatory response observed in chronic hyperprolactinemic animals subjected to chronic stress. The results suggest that short-term hyperprolactinemia has pro-inflammatory effects. Because such an effect was not observed in long-term hyperprolactinemic animals, PRL-induced tolerance seems likely. We suggest that short-term hyperprolactinemia may act as a protective factor in rats subjected to acute stress. These data suggest that hyperprolactinemia and stress interact differentially according to the time period.

[Antipituitary antibodies in patients with suspected autoimmune hypophysitis]. / Anticuerpos antihipófisis en pacientes con sospecha de hipofisitis autoimmune.

INTRODUCTION: Definitive diagnosis of autoimmune hypophysitis (AH) is histological. However, a presumptive diagnosis can be made through clinical, biochemical and imaging data. OBJECTIVE: The objective of this study was to review the presence of antipituitary antibodies (APA) and antithyroid antibodies (ATA) in patients with suspected AH in order to determinate the utility of APA in the diagnosis of AH. MATERIAL AND METHODS: We studied 36 patients divided into seven groups according to the data suggesting AH (isolated corticotropin deficiency, other idiopathic pituitary deficiencies, idiopathic hyperprolactinemia, empty sella, sellar mass with thickened stalk, proven histological hypophysitis) or because of previous autoimmune endocrine diseases. Twenty-four controls without endocrinological disease were also included. In all subjects, APA were determined by immunofluorescence over primate pituitary gland and ATA by an agglutination technique. RESULTS: None of the controls and only 9 patients, all of them women, were APA-positive. Of the 9 APA-positive patients, 43% belonged to the group of patients with isolated ACTH deficiency. In 8 patients, APA were determined again during the follow-up; 6 remained APA-negative, but one patient became APA-positive and another became APA-negative. ATA were positive in 12 patients, 22.2% of whom were also APA-positive, and in one control. CONCLUSIONS: The prevalence of APA positivity among the study patients was low. These antibodies were found only in women, mostly with isolated corticotropin deficiency. APA and ATA coexisted in only 22% of the patients studied.

Characterization of macroprolactin and assessment of markers of autoimmunity in macroprolactinaemic patients.

OBJECTIVE: It has been reported that macroprolactin is a complex of PRL and an immunoglobulin G (IgG). This study further characterizes macroprolactin and evaluates for other markers of autoimmunity using a cohort of macroprolactinaemic sera. PATIENTS AND NORMAL SUBJECTS: Following treatment of hyperprolactinaemic sera (n = 58) with polyethylene glycol (PEG), PRL values fell from 524-13 546 mU/l (Range) to 452-8455 mU/l, while in macroprolactinaemic sera (n = 41), PRL concentration fell from 525-5747 to 98-378 mU/l (PEG treated normoprolactinaemic reference range, 68-230 mU/l in males, 70-390 mU/l in females). DESIGN: PRL was measured in sera prior to and following gel filtration chromatography, ultrafiltration, treatment with protein A-sepharose, protein G-sepharose, antihuman IgG-agarose and sodium thiocyanate (NaSCN). The binding of radio-labelled PRL in macroprolactinaemic sera was also measured. Sera were assayed for antithyroid and antinuclear antibodies. C-reactive protein (CRP) and CD5 positive B cells were also measured. Comparisons were made between values obtained in normal, hyperprolactinaemic and macroprolactinaemic sera. Results Macroprolactinaemic sera indicated the presence of an IgG molecule and/or IgG fragments with one or more molecules of PRL. In 97% of the sera macroprolactin had a molecular weight of 204 kDa. Treatment of macroprolactinaemic sera with NaSCN caused dissociation of macroprolactin, releasing monomeric PRL. Macroprolactinaemic sera did not yield evidence of an increase in markers of autoimmunity when compared with hyperprolactinaemic or normal sera. CONCLUSIONS: Comprehensive analysis of macroprolactin confirmed its composition as an IgG molecule or fragment with a PRL molecule. The occurrence of macroprolactin does not appear to be associated with autoimmunity.

Macroprolactinaemia: prevalence and aetiologies in a large group of hospital workers.

OBJECTIVE: Macroprolactinaemia is one of the causes of hyperprolactinaemia and often leads to misdiagnosis and inappropriate treatment, but the aetiologies are unclear. The objective of the study was to determine the prevalence of macroprolactinaemia in a healthy population and to investigate the mechanisms underlying the development of macroprolactin. DESIGN: Observational study of the prevalence, causes, mechanisms and diagnosis of disease using excess sera after hepatitis B virus screening tests at a hospital in Japan. PARTICIPANTS: A total of 1330 hospital workers (1010 women and 320 men) participated in this study. MEASUREMENTS: Macroprolactinaemia was screened using the polyethylene glycol (PEG) precipitation method. Sera containing macroprolactin were further examined by binding studies for possible aetiologies. RESULTS: Of the 1330 subjects, 49 (3.68%) were diagnosed with macroprolactinaemia. The frequency of hyperprolactinaemia in untreated samples in subjects with macroprolactinaemia (30.6%) was significantly higher than in individuals without macroprolactinaemia (2.26%). Of the 49 subjects with macroprolactinaemia, all had a normal monomeric PRL concentration following PEG removal of macroprolactin. Of 44 hyperprolactinaemias found, 15 (34.1%) had macroprolactinaemia. IgG-bound prolactin was detected in all sera containing macroprolactin. The levels of IgG-bound prolactin positively correlated with those of macroprolactin, suggesting that IgG-bound prolactin forms macroprolactin. Approximately three quarters of the subjects with macroprolactinaemia had anti-prolactin autoantibodies. Glycosylation, aggregation and covalent/noncovalent binding were also involved in the formation of macroprolactin. CONCLUSIONS: Macroprolactinaemia is a common disorder and causes hyperprolactinaemia in a healthy population. The major aetiology of macroprolactin in our subjects was complexes of prolactin-IgG comprising mainly anti-prolactin autoantibodies, and other minor complex prolactin species.

Hyperprolactinemia is associated with a high prevalence of serum autoantibodies, high levels of inflammatory cytokines and an abnormal distribution of peripheral B-cell subsets.

PURPOSE: Hyperprolactinemia (HPRL) has been reported in many autoimmune diseases. However, the serum autoantibody profile and peripheral B-cell subset distribution in women with HPRL are largely unknown. The current study aimed to investigate the autoantibody prevalence and cytokine levels as well as to further explore the B-cell subset distribution in women with HPRL. METHODS: Sera from 202 women with HPRL and 97 healthy women were included in this study. All sera were examined for prolactin (PRL), anti-nuclear antibody (ANA), rheumatoid factor, anticardiolipin (ACL), immunoglobulin G, immunoglobulin M, complement 3, complement 4, interleukin 4 (IL-4) and interleukin 6 (IL-6). Peripheral blood was collected from 22 women with HPRL and 19 healthy women, and B-cell subsets were measured by flow cytometry. RESULTS: At least one autoantibody was found in 47 out of 202 women with HPRL compared with 9 of 97 healthy women (p < 0.001). The levels of IL-4 (p < 0.0001) and IL-6 (p < 0.0001) were significantly higher in women with HPRL than in healthy women. The percentages of naive IgD+IgM- B cells (BND cells, p < 0.0001), antibody-secreting cells (p = 0.007) and unswitched memory B cells (p = 0.004) among the total B cells from HPRL women were significantly higher than those from healthy women. CONCLUSIONS: Women with HPRL had a higher prevalence of autoantibodies, higher serum levels of IL-4 and IL-6, and more BND cells, antibody-secreting B cells and unswitched memory B cells than healthy women. These data imply that a high level of PRL is associated with autoimmune diseases.