Anti-prolactin (PRL) autoantibody-binding sites (epitopes) on PRL molecule in macroprolactinemia

Macroprolactinemia, in which serum prolactin (PRL) mainly consists of PRL with a molecular mass greater than 100 kDa, has been demonstrated to be associated with hyperprolactinemia. We previously reported that anti-PRL autoantibody is the major cause of macroprolactinemia. In this study, the autoantibody-binding sites (epitopes) on the PRL molecule were examined using deletion mutant PRL. The sera from 159 patients with hyperprolactinemia were screened for macroprolactinemia using the polyethylene glycol method and 18 patients (11%) were diagnosed with macroprolactinemia. The sera from these patients were incubated with glutathione S-transferase-human prolactin (hPRL) fragment fusion proteins immobilized on glutathione sepharose and the amounts of bound immunoglobulin G (IgG) were measured using ELISA. IgG was bound to full-length hPRL1-199 in significantly greater amounts in sera from 14 of 18 patients with macroprolactinemia than in controls. hPRL, but not PRL of other species such as bovine, porcine, rat, or human GH, dose-dependently displaced the binding, suggesting that these patients had hPRL-specific autoantibodies. Deletion of 34 amino acid residues from N-and/or C-terminals significantly reduced the binding and N- or C-terminal fragment alone showed partial but significant binding, suggesting that the major epitopes recognized by anti-PRL autoantibodies are located in both N- and C-terminal residues of the PRL molecule.     

Prevalence of macroprolactinemia among 115 patients with hyperprolactinemia

Macroprolactinemia is characterized by the predominance in the serum of macroprolactin, a prolactin (PRL) with high molecular mass and low biological activity that does not need treatment. The prevalence of macroprolactinemia was evaluated in 115 consecutive patients with hyperprolactinemia. Among them, 19 (16.5%) had solely macroprolactinemia, 4 (3.5%) polycystic ovary syndrome, 7 (6.1%) acromegaly, 8 (6.9%) idiopathic hyperprolactinemia, 10 (8.6%) primary hypothyroidism, 14 (12.2%) clinically non-functioning pituitary adenomas, 20 (17.4%) drug-induced hyperprolactinemia and 33 (28.7%) prolactinomas. The diagnosis of macroprolactinemia was established by the demonstration of a PRL recovery < 30% after treatment of sera with polyethylene glycol. Among the 19 patients with isolated macroprolactinemia, 16 (84.2%) were female and 12 (63.2%) were asymptomatic, while 4 (21%) presented with oligomenorrhea and 3 (15.8%) with galactorrhea. In contrast, only 11.5% of individuals with other causes of hyperprolactinemia were asymptomatic (p< 0.001). Prolactin levels in cases of macroprolactin ranged from 45.1 to 404 ng/mL (mean 113.3 +/- 94.5) but in 15 (78.9%) were < 100 ng/mL. Our findings demonstrate that macroprolactinemia is a common condition and, therefore, we suggest that it should be routinely screened in patients with hyperprolactinemia.     

Macroprolactinemia revisited: a study on 106 patients

The predominance of high molecular weight PRL, or macroprolactinemia, has long been known in hyperprolactinemic patients with maintained fertility. Among 1,106 consecutive patients investigated for hyperprolactinemia in our center over a 10-yr period, serum PRL chromatography was performed in 368 cases because of discordant clinical, biological, or neuroradiological findings. We prospectively studied the 106 patients with macroprolactinemia (96 women, 6 men, 4 children) and compared them with the 262 hyperprolactinemic patients with a normal PRL elution pattern. We concluded the following: 1) the incidence of macroprolactinemia in our hyperprolactinemic population was at least 10%; 2) despite preserved fertility with uneventful pregnancies, some of the usual symptoms of hyperprolactinemia were present; 3) mean PRL values were 61 +/- 66 microg/liter (range, 20-663) and exceeded 100 microg/liter in 8.5% of patients; 4) PRL levels usually remained stable over time; 5) on dopaminergic therapy, PRL returned to normal in 21 of 45 treated patients; 6) during follow-up of 7 pregnancies, PRL increased to supraphysiological levels in 5; and 7) pituitary magnetic resonance imaging was normal in 78% of patients or revealed diverse pituitary lesions, including adenomas (n = 5). A diagnostic method for macroprolactinemia should be available to all centers to avoid unnecessary hormonal or radiological investigations and treatments.     

Development of anti-PRL (prolactin) autoantibodies by homologous PRL in rats: a model for macroprolactinemia

Macroprolactinemia is hyperprolactinemia in humans mainly due to anti-PRL (prolactin) autoantibodies and is a pitfall for the differential diagnosis of hyperprolactinemia. Despite its high prevalence, the pathogenesis remains unclear. In this study, we examined whether anti-PRL autoantibodies develop via immunization with homologous rat pituitary PRL in rats to elucidate what mechanisms are involved and whether they cause hyperprolactinemia with low PRL bioactivity, as seen in human macroprolactinemia. Anti-PRL antibodies were developed in 19 of 20 rats immunized with homologous rat pituitary PRL and 29 of 30 rats with heterogeneous bovine or porcine pituitary PRL but did not develop in 25 control rats. In rats with anti-PRL antibodies, the basal serum PRL levels were elevated, and a provocative test for PRL secretion using dopamine D2 receptor antagonist (metoclopramide) showed a normal rising response with a slower clearance of PRL because of the accumulation of macroprolactin in blood. Antibodies developed by porcine or rat pituitary PRL reduced the bioactivity of rat serum PRL, and gonadal functions in these rats were normal despite hyperprolactinemia. Anti-PRL antibodies were stable and persisted for at least 5 wk after the final injection of PRL. These findings suggest that pituitary PRL, even if homologous, has antigenicity, leading to the development of anti-PRL autoantibodies. We successfully produced an animal model of human macroprolactinemia, with which we can explain the mechanisms of its clinical characteristics, i.e. asymptomatic hyperprolactinemia.     

Prevalence of pituitary adenomas in macroprolactinemic patients may be higher than it is presumed

One form of prolactin (PRL) is macroprolactin with high molecular mass. Many macroprolactinemic patients have no pituitary adenomas and no clinical symptoms of hyperprolactinemia, it is controversial whether macroprolactinemia is a benign condition that does not need further investigation and treatment. In this study, we aimed to compare macroprolactinemic patients (group I) with the true hyperprolactinemic patients (group II) for the presence of pituitary adenoma. We investigated 161 patients with hyperprolactinemia, whose magnetic resonance imaging records of the pituitary were taken. All patients were questioned for irregular menses, infertility and examined for galactorrhea. Patients were screened for macroprolactinemia by polyethylene glycol precipitation, and a recovery of ≤40% and normal monomeric PRL level was taken as an indication of significant macroprolactinemia. Of 161 patients with hyperprolactinemia, 60 (37.26%) had macroprolactinemia. PRL levels of group II were lower than those of group I (P = 0.011), although monomeric PRL levels of group II were higher than those of group I (P = 0.0005). Of 60 macroprolactinemic patients, 16 (26.7%) had pituitary adenomas. The prevalence of pituitary adenomas was lower in group I, compared with group II (P = 0.0005). No significant differences were found between the prevalences of irregular menses and infertility of group I and II (P = 0.084, P = 0.361). Prevalence of galactorrhea in group I was lower than that in group II (P = 0.048). Prevalence of pituitary adenomas in macroprolactinemic patients is lower compared with the true hyperprolactinemic patients, but may be higher than that found in other recent studies and in the general population.     

Detection of macroprolactinemia with the polyethylene glycol precipitation test in systemic lupus erythematosus patients with hyperprolactinemia

The objective of this study was to determine the diagnostic performance of the percentage of serum prolactin (PRL) precipitated with polyethylene glycol (PEG) for the detection of macroprolactinemia in systemic lupus erythematosus (SLE) patients with hyperprolactinemia. Serum samples from SLE patients were examined. Serum PRL was measured by immunoradiometric assay (IRMA) and samples with hyperprolactinemia (> 20 ng/ml) were submitted to PEG precipitation, gel filtration chromatography and affinity chromatography with protein-G sepharose. A comparative survey was used. Among 259 consecutive serum samples from SLE patients, PRL was > 20.1 ng/ml in 43 samples (16.6%). Gel filtration showed a predominant pattern of macroprolactinemia (> 100 kDa) in 14 (32.6%), a predominant pattern of monomeric PRL (23 kDa) in 27 (62.7%), and a variable pattern in two (4.7%). All sera with a predominant pattern of macroprolactinemia displayed anti-PRL autoantibodies by affinity chromatography for IgG. The best cut-off point for percentage of serum PRL precipitated with PEG for detection of macroprolactinemia was > or = 58.4%. Sensitivity and specificity were 100 and 96.6%, respectively. We can conclude that PEG precipitation is a convenient and simple procedure to screen for the presence of macroprolactinemia in sera from SLE patients. Precipitations > or = 58.4% are indicative of the presence of, and those < 50% the absence of, macroprolactinemia. However, samples with precipitations between 50 and 58.3% require gel filtration chromatography to characterize the predominant molecular form of PRL. Therefore, it is important to take these findings into account in future studies that aim to establish a relationship between PRL and disease activity in SLE.     

The importance of measuring macroprolactin in the differential diagnosis of hyperprolactinemic patients

This study investigated the differences in clinical and laboratory features as well as treatment response in 70 outpatients with macroprolactinemia and monomeric hyperprolactinemia treated with dopamine agonists. After precipitation of the patients' serum samples with poly-ethylene-glycol (PEG), serum prolactin (PRL) levels were measured. We also measured serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol for women and testosterone for men. Clinical symptoms and signs were recorded. All patients received brain magnetic resonance imaging (MRI). After excluding patients with macroadenoma, 66 patients were treated with the dopamine agonist cabergoline. After 1 year, the clinical responses to cabergoline were recorded and PRL levels measured. Of the initial 70 patients with hyperprolactinemia, 15 patients (21.4%) were found to have macroprolactinemia, while the rest had monomeric hyperprolactinemia. The two groups did not differ with regard to galactorrhea, menstrual disturbances or impotence. There were no significant group differences in serum LH, FSH, estradiol or testosterone levels. Patients with macroprolactinemia, however, had a significantly lower infertility rate than those with true hyperprolactinemia (6.7% vs. 32.7%, p=0.005). A greater percentage of macroprolactinemic patients had normal MRI pituitary images than those with hyperprolactinemia (73.3% vs. 34.5%, p=0.029). Compared to those with true hyperprolactinemia, patients with macroprolactinemia were found to have no significant changes in clinical features and PRL levels after 1 year of cabergoline therapy (after PEG precipitation, pre- and post-PRL levels: 59.3 ± 100.2 to 13.8 ± 9.5 ng/mL vs. 6.1 ± 5.3 to 5.1 ± 4.3 ng/mL, p=0.002). In conclusion, while macroprolactinemia is a common cause of hyperprolactinemia, many clinical and laboratory features cannot be used reliably to differentiate macroprolactinemia from true hyperprolactinemia. Routine screening for all hyperprolactinemic sera with PEG might prevent the unnecessary use of image studies and medical treatments for people with hyperprolactinemia.     

Macroprolactinemia: predictability on clinical basis and detection by PEG precipitation with two different immunometric methods

Prolactin (PRL) in human serum is present in three species: monomeric PRL (23 kDA), big PRL (50-60 kDa) and big, big PRL (bb-PRL or macroprolactinemia) of 150-170 kDa. Macroprolactin seems to be mainly composed of a molecule of monomeric PRL and an immunoglobulin G anti PRL. Its biological activity is considered low or absent, but it is measured, at various degrees, by the immunoassay method, thus causing diagnostic problems. Polyethylene Glycol (PEG) has been employed to precipitate macroprolactin, allowing its detection. This method is not applicable to all immunoassays for technical reasons. Our aim was to evaluate: 1) the predictability of macroprolactin on a clinical basis; 2) the possibility of applying PEG precipitation to Abbott AxSYM analyzer beside Roche Elecsys (already approved). We classified 34 hyperprolactinemic women, on a clinical and imaging basis, in four groups: A: functional hyperprolactinemia; B: pituitary lesions hyperprolactinemia; C: probably macroprolactinemia; D: unclassifiable hyperprolactinemia and a "control" group E of 19 healthy women. PRL was assayed, both with Elecsys and AxSYM, before and after PEG serum treatment. Eleven out of twelve group C, and 5/7 group D patients showed macroprolactinemia, against 1/7 in A and 1/8 in B. PEG was suitable for AxSYM only after the same treatment of the calibration standards, thus performing outcomes overlapping Elecsys. For clinical purposes, in the presence of macroprolactinemia, besides the recovery ratio, molar or ponderal monomeric PRL assay should be calculated.     

Analysis of anti-prolactin autoantibodies in systemic lupus erythematosus.

Evidence has shown that prolactin is an essential component of an effective immune response. In systemic lupus erythematosus, clinical trials have produced controversial information about the role of PRL. Some results find association between serum PRL levels and disease activity. In contrast, other authors did not find this. Recently, autoantibodies against prolactin in SLE patients have been described. One hundred percent of SLE patients with anti-PRL autoantibodies had hyperprolactinemia (hPRL) and 31.7% of the SLE patients classified with idiopathic hPRL had anti-prolactin antibodies. A similar result was found in 103 pediatric SLE patients. The patients with idiopathic hyperprolactinemia and anti-PRL autoantibodies had less clinical and serological lupus activity than the SLE patients with idiopathic hyperprolactinemia, but without anti-PRL autoantibodies. This evidence suggests that anti-PRL autoantibodies or the complex with any other molecule, like macroprolactinemia (big-big PRL) could have attenuated biological activity and this could explain why some clinical studies did not find any association between serum PRL levels and disease activity in SLE patients. However, studies in vitro have shown normal or elevated biological activity in Nb2 cell lines using PRL from serum with anti-PRL autoantibodies from patients with or without autoimmune diseases. Several conclusions could be drawn. One is that while a set of hyperprolactinemic SLE patients display autoantibodies against PRL, it is not clear what role these autoantibodies play in the whole system. However, until now, we knew that the patients with antibodies to PRL lacked the clinical symptoms of hyperprolactinemia such as menstrual disturbances and/or galactorrhea and show less clinical and serological lupus activity.     

Hyperprolactinemia due to big big prolactin is differently detected by commercially available immunoassays

Macroprolactinemia, i.e. sustained hyperprolactinemia where the predominant circulating form of prolactin (PRL) is of large molecular weight, is a common phenomenon comprising up to one-fourth of all cases of hyperprolactinemia. We measured serum PRL levels by four different immunoassay systems (PROL-CTK, RIAgnost, Delfia, ACS 180) and by the Nb2 bioassay in patients with prolactinomas/idiopathic hyperprolactinemias in whom monomeric PRL was the major species of PRL (n=11, group 1) and in patients with macroprolactinemia (n=12, group 2). In group 1, the results obtained with the different immunoassays and with the Nb2 assay were highly correlated (r=0.945-0.982). On the other hand, big big-PRL (bb-PRL) was differently recognized by the immunoassays, since measured serum PRL values from each patient were highly variable in group 2. RIA-gnost Prolactin and Delfia Prolactin detected bb-PRL similarly and they were highly correlated with each other (r=0.937, p<0.0001). ACS 180 detected bb-PRL somewhat differently from the RIA-gnost and Delfia systems, but likewise most of the patients of group 2 had PRL values above normal. PROL-CTK was the method less influenced by the presence of bb-PRL since most of the subjects with macroprolactinemia had PRL levels either within the normal range or only marginally elevated. From the immunoassays tested, PROL-CTK was the system which was less correlated with the Nb2 bioassay in group 2 (r=0.252; NS). Our experience is that macroprolactinemia is an asymptomatic condition in most of the cases. Therefore, we suggest that the routine measurement of PRL should be done with methods that are only minimally affected by the presence of macroprolactin. Such an approach would obviate the use of extensive, frequently expensive and ultimately useless diagnostic tests that are needed to determine the cause of the hyperprolactinemia.     

Mild hyperprolactinemia in a couple: What impact on fertility?

Mild-to-moderate hyperprolactinemia is a frequent finding in young women presenting with infertility. Prolactin (PRL) concentration should be determined accurately, whether or not the patient has other symptoms suggestive of excess PRL such as galactorrhea or menstrual cycle disorder. After confirmation of persistent hyperprolactinemia on a second blood sample (avoiding conditions known to raise prolactin) and exclusion of macroprolactinemia, prolactinoma and other identifiable non-tumoral causes of hyperprolactinemia must be ruled out. Mildly elevated PRL levels may cause luteal insufficiency in cycling women and are associated with recurrent miscarriage. Any confirmed hyperprolactinemia should be treated in a woman who wishes or fails to become pregnant. Preference is given to cabergoline at the lowest possible dose that normalizes PRL, restoring fertility in the vast majority of cases.Evidence is much less robust in men, in whom PRL concentrations are less prone to increase and the reproductive system is less sensitive to the negative effects of hyperprolactinemia. Nevertheless, chronic and significant hyperprolactinemia in men may impair fertility or cause infertility (with or without hypogonadism) and must be treated, as in women. However, more clinical studies are clearly needed concerning male reproductive function.The significance of mild but persistent hyperprolactinemia in either member of a couple incidentally discovered during assisted reproductive technology (ART) procedures is unclear, and future evidence-based studies are needed to determine whether normalizing prolactin can improve ART outcome.     

Clinical and radiological findings in macroprolactinemia

Hyperprolactinemia is the most common abnormality of the hypothalamic-pituitary axis. The aim of this study was to investigate the clinical and radiological features of patients with macroprolactinemia. The study population consisted of patients with elevated serum prolactin (PRL) concentrations who presented to our Endocrinology outpatient clinic. Detection of macroprolactin (macroPRL) was performed using the polyethylene glycol precipitation method. Patients in which macroPRL made up more than 60% of total PRL levels were stratified into the macroPRL group, while the remaining patients were placed in the monomeric prolactin (monoPRL) group. A total of 337 patients were enrolled with a mean age of 33.8?±?10.8 (16-66) years and a male/female ratio of 29/308. Eighty-eight of the patients (26.1%) had an elevated macroPRL level. The mean age in the monoPRL group was higher than in the macroPRL group (35.0?±?10.1 vs. 30.7?±?9.8, P?=?0.016). The mean PRL levels (ng/ml) in the macroPRL and monoPRL groups were similar (168.0?±?347.0 vs. 238.8?±?584.9, P?=?0.239). Frequency of amenorrhea, infertility, irregular menses, gynecomastia, and erectile dysfunction were also similar in both groups. More patients in the macroPRL group were asymptomatic compared to the monoPRL group (30.2 vs. 12.0%, P?=?0.006). Compared to the macroPRL group, the monoPRL group had a higher frequency of galactorrhea (39.2 vs. 57.1%, P?=?0.04) and abnormal magnetic resonance imaging findings (65.3 vs. 81.1%, P?=?0.02). Elevated macroPRL levels should be considered a pathological biochemical variant of hyperprolactinemia that may present with any of the conventional symptoms and radiological findings generally associated with elevated PRL levels.     

Frequency of macroprolactinemia due to autoantibodies against prolactin in pregnant women

The frequency of macroprolactinemia related to the presence of anti-PRL autoantibodies in the serum of 209 healthy women at different stages of pregnancy was studied. Measurements were taken of serum PRL concentrations before and after chromatographic separation (gel filtration and affinity with proteins A and G) and extraction of free PRL with polyethylene glycol (PEG). Sera from 8 of the 209 women (3.8%) were found to have a significantly high proportion of precipitated PRL by PEG (macroprolactinemia); in these patients, gel filtration showed that a substantial amount of big big PRL (molecular mass >100 kDa) was present (19.0--78.2% vs. 3.8-4.9%, P = 0.009 in normal pregnant women with a normal proportion of precipitated PRL by PEG). The presence of macroprolactinemia was attributable to anti-PRL autoantibodies in 5 of the 8 women. Comparison of serum levels of direct and free PRL between women with macroprolactinemia related to anti-PRL autoantibodies and women without macroprolactinemia showed significant differences (direct PRL: 270.2 +/- 86.9 vs. 203.4 +/- 69.0 microg/L, P = 0.04; and free PRL: 107.0 +/- 75.9 vs. 173.3 +/- 67.6 microg/L, P = 0.002). On the other hand, there was no difference between women with macroprolactinemia not related to anti-PRL autoantibodies and women with macroprolactinemia caused by anti-PRL autoantibodies, nor was there a difference between women with macroprolactinemia not related to anti-PRL autoantibodies and women without macroprolactinemia. There was a positive correlation between titers of the anti-PRL autoantibody and serum PRL levels (r = 0.82, P = 0.09). The presence of the anti-PRL autoantibody had no relation to the patient's age, stage of gestation, or number of previous pregnancies. We concluded that the frequency of macroprolactinemia was 3.8% among healthy, pregnant women, which was caused by a anti-PRL autoantibodies in 62.5% of the cases. The autoantibodies were found in the bloodstream, forming a PRL-IgG complex, in accordance with the following observations: 1) immunoreactive PRL on gel filtration was eluted in the fractions corresponding to the molecular mass of IgG (150 kDa); 2) a significantly high proportion of immunoreactive PRL was retained on an affinity gel for IgG (proteins A and G); and 3) a significantly high proportion of serum PRL bound to IgG was precipitated by protein A. There was a positive correlation between titers of anti-PRL autoantibodies and serum PRL levels. Serum levels of total PRL were higher, and serum levels of free PRL were lower, in pregnant women with anti-PRL autoantibodies than in pregnant women without macroprolactinemia.     

Macroprolactinemia: the consequences of a laboratory pitfall

The objective of this study was to assess the prevalence of macroprolactin, a macromolecule with reduced bioactivity, in hyperprolactinemic patients. Prolactin was measured before and after precipitation of macroprolactin by polyethylene glycol in 306 patients. Only patients with prolactin values >700 mIU/L (n = 270) entered the study. In 23% of the patients, macroprolactinemia was found. In women, the occurrence of macroprolactinemia increased with advancing age (< 30 yr: 16%; 30-45 yr: 28%; > 45 yr: 42%; p < 0.05). A priori clinical signs of hyperprolactinemia (morphological abnormalities in pituitary imaging, galactorrhea infertility) occurred significantly less frequently in macroprolactinemia than in true hyperprolactinemia. In eight females macroprolactinemia and true hyperprolactinemia appeared simultaneously. To avoid diagnostic and therapeutic pitfalls, the screening for macroprolactinemia of all patients with prolactin levels of > 700 mIU/ L is recommended.     

Etiological diagnosis of hyperprolactinemia

There are numerous etiologies of hyperprolactinemia, a common reason for consultation. Diagnostic measures must be capable of identifying the tumors, the most frequent of which are prolactin adenomas. Hypothalamic-pituitary MRI is the reference morphological examination. In clinical practice, it is usually performed very early, following the discovery of increased plasma concentrations of PRL. This approach is warranted for marked increase in PRL in the absence of drugs with hyperprolactinemic effects (>10 x upper limit of normal) since a diagnosis of PRL adenoma is extremely likely under such circumstances. When hyperprolactinemia is moderate, which is the most common finding in practice, all etiologies are possible in theory and it is important to follow a rational diagnostic plan (history-taking to identify use of any drugs with hyperprolactinemic effects paying attention to renal and hepatic history, investigation for endocrine diseases occasionally associated with hyperprolactinemia such as hypothyroidism or polycystic ovary syndrome (PCOS), confirmation of hyperprolactinemia by a second assay when the initial level is less than five times the upper normal limit, pregnancy testing for women of childbearing age) in order to rule out all non-tumoral causes of hyperprolactinemia before proceeding with imaging. Absence of any consequences of hyperprolactinemia on gonadic function or the existence of a concomitant disease that could account for the clinical signs, demonstration of wide variations in PRL from one assay to another in a single patient could prompt screening for macroprolactinemia before MRI is ordered. Macroprolactinoma could also occur in the case of normal or doubtful MRI or discrepancy in response to medical or surgical treatment. T1- and T2-weighted coronal sections (with or without T1 after gadolinium injection) are generally sufficient for diagnosis of microprolactinoma. Dynamic tests may be useful if MRI is normal or unclear. Gadolinium injection with sagittal and axial sections is essential for examination of large lesions. In this case, when the increase of PRL is moderate (<150 mg/ml), a non-lactotropic lesion may be suspected without misdiagnosing a hook effect. Careful analysis of the images allows differentiation between tumoral lesions and pituitary hyperplasia.     

From macroprolactinoma to concomitant ACTH-PRL hypersecretion with Cushing's disease

Multiple pituitary hormone hypersecretions have been already described, but the combination of PRL and ACTH excess is rare. This report deals with a 42-yr-old woman affected by macroprolactinoma (PRL 12,720 microg/l, huge tumor with extrasellar extension at imaging). After one year on dopaminergic treatment causing PRL normalization and tumor shrinkage, she developed hypercortisolism (UFC 1,000 microg/24 h, ACTH 200 ng/l). Cushing's disease was diagnosed. After neurosurgery (at immunocytochemistry mixed ACTH-PRL adenoma was shown) hypercortisolism remitted, whereas pathological hyperprolactinemia with tumor remnant in cavernous sinus persisted and hypopituitarism developed. The patient reported seems atypical for the following reasons: 1) the concomitant PRL and ACTH hypersecretions; 2) the clinical presentation with hypercortisolism following hyperprolactinemia; 3) the surgical cure of hypercortisolism with persisting hyperprolactinemia.     

Diagnostic étiologique d'une hyperprolactinémie

There are numerous etiologies of hyperprolactinemia, a common reason for consultation. Diagnostic measures must be capable of identifying the tumors, the most frequent of which are prolactin adenomas. Hypothalamic-pituitary MRI is the reference morphological examination. In clinical practice, it is usually performed very early, following the discovery of increased plasma concentrations of PRL. This approach is warranted for marked increase in PRL in the absence of drugs with hyperprolactinemic effects (> 10 x upper limit of normal) since a diagnosis of PRL adenoma is extremely likely under such circumstances. When hyperprolactinemia is moderate, which is the most common finding in practice, all etiologies are possible in theory and it is important to follow a rational diagnostic plan (history-taking to identify use of any drugs with hyperprolactinemic effects paying attention to renal and hepatic history, investigation for endocrine diseases occasionally associated with hyperprolactinemia such as hypothyroidism or polycystic ovary syndrome (PCOS), confirmation of hyperprolactinemia by a second assay when the initial level is less than 5 times the upper normal limit, pregnancy testing for women of childbearing age) in order to rule out all non-tumoral causes of hyperprolactinemia before proceeding with imaging. Absence of any consequences of hyperprolactinemia on gonadic function or the existence of a concomitant disease that could account for the clinical signs, demonstration of wide variations in PRL from one assay to another in a single patient could prompt screening for macroprolactinemia before MRI is ordered. Macroprolactinoma could also occur in the case of normal or doubtful MRI or discrepancy in response to medical or surgical treatment. T1- and T2-weighted coronal sections (with or without T1 after gadolinium injection) are generally sufficient for diagnosis of microprolactinoma. Dynamic tests may be useful if MRI is normal or unclear. Gadolinium injection with sagittal and axial sections is essential for examination of large lesions. In this case, when the increase of PRL is moderate (< 150 mg/ml), a non-lactotropic lesion may be suspected without misdiagnosing a hook effect. Careful analysis of the images allows differentiation between tumoral lesions and pituitary hyperplasia.     

Approach to the patient with persistent hyperprolactinemia and negative sellar imaging

Hyperprolactinemia is a common cause of menstrual disturbances affecting young women. There is a diversity of causes, from physiological, such as pregnancy, to pharmacological and pathological, such as hypothyroidism. Renal and hepatic failure, intercostal nerve stimulation by trauma or surgery, prolactinomas, other tumors in the hypothalamus-pituitary region, as well as macroprolactinemia can also be considered. Identifying the correct cause is important to establish the correct treatment. Should all these causes be ruled out and pituitary imaging revealed as negative, idiopathic hyperprolactinemia is therefore diagnosed. In symptomatic patients, treatment with dopaminergic agonists is indicated. As for the asymptomatic hyperprolactinemic individuals, macroprolactinemia should be screened, and once it is detected, there is no need for pituitary imaging study or for dopaminergic agonist use.     

The prevalence of hyperprolactinemia in patients with primary Sj?gren's syndrome.

OBJECTIVE: To assess the prevalence of hyperprolactinemia in 55 patients with primary Sj?gren's syndrome (SS), and its clinical significance. METHODS: Concentrations of serum prolactin (PRL) were determined in 55 consecutive patients with primary SS and 110 controls by a fluoroimmunometric assay in a prospective case-control design. RESULTS: The 55 patients with primary SS had higher serum PRL than 110 matching controls (271.5 vs 205.9 mIU/l; p < 0.02), and this difference was most evident in patients diagnosed before the age of 45 years (374.8 vs 245.5 mIU/l; p < 0.05), a patient population characterized by active immunological disease. Serum PRL did not correlate to disease duration, serum immunoglobulin, autoantibodies, or focus score in biopsies from minor salivary glands, but did correlate to score for internal organ disease (r = 0.33, p < 0.05). Two patients were diagnosed as having primary SS 12 years after hyperprolactinemia was first detected, and both patients had aggressive primary SS as indicated by extraglandular manifestations. One of the patients developed primary SS after being treated with bromocriptine, an inhibitor of PRL synthesis, for 12 years. CONCLUSION: Patients with primary SS have moderately increased levels of serum PRL, especially evident in patients diagnosed at a young age with active immunological disease. Serum PRL is correlated to index for internal organ disease, and primary SS may be preceded by hyperprolactinemia for many years.     

Immunoglobulin G subclasses and prolactin (PRL) isoforms in macroprolactinemia due to anti-PRL autoantibodies

Although macroprolactinemia due to antiprolactin (anti-PRL) autoantibodies is not uncommon among hyperprolactinemic patients, the pathogenesis of such macroprolactinemia is still unknown. We examined IgG subclasses of anti-PRL autoantibodies by enzyme immunoassay, and PRL phosphorylation and isoforms by Western blotting, mass spectrometry, and two-dimensional electrophoresis in six patients with anti-PRL autoantibodies and in 29 controls. PRL-specific IgG subclasses in patients with anti-PRL autoantibodies were heterogeneous, but five of six patients showed IgG4 predominance, which is known to be produced by chronic antigen stimulation. Western blot and mass spectrometric analyses revealed that human pituitary PRL was phosphorylated at serine 194 and serine 163, whereas serine 163 in serum PRL was dephosphorylated. On two-dimensional electrophoresis, serum PRL mainly consisted of isoform with isoelectric point (pI) 6.58 in control hyperprolactinemic patients, whereas acidic isoforms (pIs 6.43 and 6.29) were also observed in patients with anti-PRL autoantibodies. Our data first demonstrate that human pituitary PRL is serine phosphorylated and partially dephosphorylated in serum, and suggest that the acidic isoforms may give rise to chronic antigen stimulation in patients with anti-PRL autoantibodies.