Screening for macroprolactinaemia and pituitary imaging studies

Establishment of reference intervals of monomeric prolactin to identify macroprolactinemia in Chinese patients with increased total prolactin

BACKGROUND

Macroprolactin is responsible for pseudohyperprolactinemia and is a common pitfall of the prolactin immunoassay. We aimed to determine the frequency of macroprolactinemia in Chinese hyperprolactinemic patients using monomeric prolactin discriminated by precipitation with polyethylene glycol (PEG).

METHODS

Post-PEG monomeric prolactin gender-specific reference intervals were established for the Elecsys immunoassay method (Roche Diagnostics) using sera from healthy female (n = 120) and male (n = 120) donors. The reference intervals were validated using 20 macroprolactinemic (as assessed by gel filtration chromatography (GFC)) sera samples, and presence of monomeric prolactin was discriminated by GFC. Patients with high total prolactin were then screened by PEG precipitation to analyze macroprolactin. The demographic and biochemical details of patients with true hyperprolactinemia and macroprolactinemia were compared.

RESULTS

Reference intervals for monomeric prolactin in females and males were 3.4-18.5 and 2.7-13.1 ng/mL, respectively. Among 1140 hyperprolactinemic patients, macroprolactinemia was identified in 261 (22.9 %) patients while the other 879 (77.1 %) patients were diagnosed with true hyperprolactinemia. Menstrual disturbances were the most common clinical feature in both groups. Galactorrhea, amenorrhea, and visual disturbances occurred more frequently in true hyperprolactinemic patients (P < 0.05).

CONCLUSIONS

The prevalence of macroprolactin in Chinese patients with hyperprolactinemia was described for the first time. Monomeric prolactin concentration, along with a reference interval screening with PEG precipitation, provides a diagnostic approach for hyperprolactinemia with improved accuracy.

True hyperprolactinemia in men without visible pituitary adenoma

PURPOSE

Men with mild to moderate hyperprolactinemia rarely present with normal pituitary on MRI with no visible adenoma, a condition entitled also "idiopathic hyperprolactinemia" or "non-tumoral hyperprolactinemia". We have characterized a cohort of hyperprolactinemic men with normal pituitary imaging.

DESIGN

We have identified 13 men with true hyperprolactinemia and normal pituitary MRI. Baseline clinical and hormonal characteristics and response to medical treatment were retrospectively retrieved from medical records.

RESULTS

Mean age at diagnosis was 51 ± 16 years (range, 20-77); mean serum prolactin level at presentation was 91 ng/ml (range, 28-264), eight men presented with low baseline testosterone. Initial complaints leading to diagnosis included sexual dysfunction in ten men and gynecomastia in five. All patients were treated with cabergoline, except for one who was given bromocriptine; none required pituitary surgery. All patients normalized prolactin and testosterone with subsequent clinical improvement reported by most men. Currently, after a mean follow-up of 72 months, ten patients continue treatment with caborgoline (median weekly dose, 0.25 mg), whereas three men discontinued treatment.

CONCLUSIONS

Men with symptomatic hyperprolactinemia may rarely present with normal pituitary imaging. Medical treatment can lead to hormonal improvement with clinical benefit.

Global Prevalence of Macroprolactinemia among Patients with Hyperprolactinemia: A Systematic Review and Meta-Analysis

Hyperprolactinemia (hPRL) often poses a diagnostic dilemma due to the presence of macroprolactin. Understanding the prevalence of macroprolactinemia (mPRL) has an important implication in managing patients with hPRL. The primary aim of this study was to determine the prevalence of mPRL globally and to explore selected factors influencing the prevalence estimate. Studies with original data related to the prevalence of mPRL among patients with hPRL from inception to March 2020 were identified, and a random effects meta-analysis was performed. Of the 3770 records identified, 67 eligible studies from 27 countries were included. The overall global prevalence estimate was 18.9% (95% CI: 15.8%, 22.1%) with a substantial statistical heterogeneity (I² = 95.7%). The highest random effects pooled prevalence was observed in the African region (30.3%), followed by Region of the Americas (29.1%), European (17.5%), Eastern Mediterranean (13.9%), South-East Asian (12.7%), and Western Pacific Region (12.6%). Lower prevalence was observed in studies involving both sexes as compared to studies involving only female participants (17.1% vs. 25.4%) and in more recent studies (16.4%, 20.4%, and 26.5% in studies conducted after 2009, between 2000 and 2009, and before 2000, respectively). The prevalence estimate does not vary according to the age group of study participants, sample size, and types of polyethylene glycol (PEG) used for detection of macroprolactin (PEG 6000 or PEG 8000). With macroprolactin causing nearly one-fifth of hPRL cases, screening for mPRL should be made a routine before an investigation of other causes of hPRL.

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.

Impact of Macroprolactinemia on Cardiometabolic Effects of Atorvastatin in Women With Hypercholesterolemia

Premenopausal women with macroprolactinemia are characterized by increased cardiometabolic risk. No previous study has investigated the impact of any lipid-lowering agent on circulating levels of cardiometabolic risk factors in patients with elevated macroprolactin content. We studied 2 groups of women matched for age, body mass index, plasma lipids, and blood pressure: 12 women with macroprolactinemia and 14 women with prolactin levels within the reference range. Because of coexistent isolated hypercholesterolemia, all subjects were then treated with atorvastatin (20 mg daily). Glucose homeostasis markers, plasma lipids, as well as circulating levels of uric acid, high-sensitivity C-reactive protein (hsCRP), fibrinogen, homocysteine, and 25-hydroxyvitamin D were measured before entering the study and 6 months later. The treatment arms differed in baseline values of hsCRP and 25-hydroxyvitamin D, as well as in insulin sensitivity. Atorvastatin decreased total and low-density lipoprotein cholesterol levels stronger in women without than in women with macroprolactinemia. In normoprolactinemic women, atorvastatin decreased circulating levels of uric acid, hsCRP, fibrinogen, homocysteine, and increased concentrations of 25-hydroxyvitamin D, whereas in women with macroprolactinemia the drug decreased levels of hsCRP and homocysteine, as well as impaired insulin sensitivity. Both study groups differed in post-treatment insulin sensitivity and post-treatment values of prolactin before polyethylene glycol precipitation, macroprolactin, total cholesterol, low-density lipoprotein cholesterol, glycated hemoglobin, uric acid, hsCRP, fibrinogen, homocysteine, and 25-hydroxyvitamin D. In conclusion, the obtained results suggest that macroprolactinemia may attenuate cardiometabolic effects of atorvastatin.

PCOS and Hyperprolactinemia: what do we know in 2019?

Polycystic ovary syndrome (PCOS) and hyperprolactinemia (HPRL) are the two most common etiologies of anovulation in women. Since the 1950s, some authors think that there is a pathophysiological link between PCOS and HPRL. Since then, many authors have speculated about the link between these two endocrine entities, but no hypothesis proposed so far could ever be confirmed. Furthermore, PCOS and HPRL are frequent endocrine diseases and a fortuitous association cannot be excluded. The evolution of knowledge about PCOS and HPRL shows that studies conducted before the 2000s are obsolete given current knowledge. Indeed, most of the studies were conducted before consensual diagnosis criteria of PCOS and included small numbers of patients. In addition, the investigation of HPRL in these studies relied on obsolete methods and did not look for the presence of macroprolactinemia. It is therefore possible that HPRL that has been attributed to PCOS corresponded in fact to macroprolactinemia or to pituitary microadenomas of small sizes that could not be detected with the imaging methods of the time. Recent studies that have conducted a rigorous etiological investigation show that HPRL found in PCOS correspond either to non-permanent increase of prolactin levels, to macroprolactinemia or to other etiologies. None of this recent study found HPRL related to PCOS in these patients. Thus, the link between PCOS and HPRL seems to be more of a myth than a well-established medical reality and we believe that the discovery of an HPRL in a PCOS patient needs a standard etiological investigation of HPRL.

Prevalence and reproductive manifestations of macroprolactinemia

PURPOSE

Macroprolactinemia is characterized by predominance of macroprolactin molecules in circulation and generally has extra-pituitary origin. Macroprolactin is viewed as biologically inactive, therefore asymptomatic, and thus may not require any treatment or prolonged follow-up. In addition, data on prevalence of macroprolactinemia and its clinical manifestation are also rare. Therefore, the present study was aimed to find out prevalence of macroprolactinemia and its association, if any, with reproductive manifestations.

MATERIAL AND METHODS

Macroprolactin was measured in 102 hyperprolactinemia cases (>100 ng/ml prolactin level), 135 physiological hyperprolactinemia cases (50 pregnant and 85 lactating females; >100 ng/ml prolactin level) and 24 controls. Poly ethylene glycol (PEG) precipitation method was carried out to screen macroprolactin. Prolactin recovery of <25% was considered overt macroprolactinemia. Detailed clinical data was recorded which included complete medical history, physical examination and hormone measurements besides CT/MRI for pituitary abnormalities.

RESULTS

Prevalence of macroprolactinemia was 21.57% (22/102) in hyperprolactinemia (prolactin >100 ng/ml). There was no case of macroprolactinemia in physiological hyperprolactinemia, or healthy control females. Reproductive manifestations were present in 72.73% (16/22) macroprolactinemia cases, out of which macroprolactinemia was the sole cause of associated reproductive manifestations in 68.7% (11/16) cases. Reversal of reproductive dysfunction/s was observed in five cases with appropriate treatment for high macroprolactin.

CONCLUSION

Macroprolactinemia prevalence was found to be 21.5%, out of which 72.73% cases had associated reproductive dysfunctions.

Pitfalls in the Diagnostic Evaluation of Hyperprolactinemia

An appropriate diagnostic evaluation is essential for the most appropriate treatment to be performed. Currently, macroprolactinemia is the third most frequent cause of nonphysiological hyperprolactinemia after drugs and prolactinomas. Up to 40% of macroprolactinemic patients may present with hypogonadism symptoms, infertility, and/or galactorrhea. Thus, the screening for macroprolactin is indicated not only for asymptomatic subjects but also for those without an obvious cause for their prolactin (PRL) elevation. Before submitting patients to macroprolactin screening and pituitary magnetic resonance imaging, one should rule out pregnancy, drug-induced hyperprolactinemia, primary hypothyroidism, and renal failure. The magnitude of PRL elevation can be useful in determining the etiology of hyperprolactinemia. PRL values >250 ng/mL are highly suggestive of prolactinomas and virtually exclude nonfunctioning pituitary adenomas (NFPAs) and other sellar masses as the etiology of hyperprolactinemia. However, they can also be found in subjects with macroprolactinemia, drug-induced hyper-prolactinemia or chronic renal failure. By contrast, most patients with NFPAs, drug-induced hyperprolactinemia, macroprolactinemia, or systemic diseases present with PRL levels <100 ng/mL. However, exceptions to these rules are not rare. Indeed, up to 25% of patients harboring a microprolactinoma or a cystic macroprolactinoma may also have PRL <100 ng/mL. Falsely low PRL levels may result from the so-called "hook effect," which should be considered in all cases of large (≥3 cm) pituitary adenomas associated with normal or mildly elevated PRL levels (≤250 ng/mL). The hook effect may be unmasked by repeating PRL measurement after a 1:100 serum sample dilution.

Laboratory and clinical significance of macroprolactinemia in women with hyperprolactinemia

The role of macroprolactinemia in women with hyperprolactinemia is currently controversial and can lead to clinical dilemmas, depending upon the origin of macroprolactin, the presence of hyperprolactinemic symptoms and monomeric prolactin (PRL) levels. Macroprolactinemia is mostly considered an extrapituitary phenomenon of mild and asymptomatic hyperprolactinemia associated with normal concentrations of monomeric PRL and a predominance of macroprolactin confined to the vascular system, which is biologically inactive. Patients can therefore be reassured that macroprolactinemia should be considered a benign clinical condition, resistant to antiprolactinemic drugs, and that no diagnostic investigations or prolonged follow-up should be necessary. However, a significant proportion of macroprolactinemic patients appears to suffer from hyperprolactinemia-related symptoms and radiological pituitary findings commonly associated with true hyperprolactinemia. The symptoms of hyperprolactinemia are correlated to the levels of monomeric PRL excess, which may be explained as coincidental, by dissociation of macroprolactin, or by physiological, pharmacological and pathological causes. The excess of monomeric PRL levels in such cases is of primarily importance and the diagnosis of macroprolactinemia is misleading or inadequate. However, macroprolactinemia of pituitary origin associated with radiological findings of pituitary adenomas may rarely occur with similar hyperprolactinemic manifestations, exclusively due to bioactivity of macroprolactin. Therefore, in such cases with hyperprolactinemic signs and pituitary findings, macroprolactinemia should be considered a pathological biochemical condition of hyperprolactinemia. Accordingly, individualized diagnostic investigations with the introduction of dopamine agonists, or other treatment with prolonged follow-up, should be mandatory. The review analyses the laboratory and clinical significance of macroprolactinemia in hyperprolactinemic women suggesting clinically useful diagnostic and treatment strategies.

Controversial issues in the management of hyperprolactinemia and prolactinomas - An overview by the Neuroendocrinology Department of the Brazilian Society of Endocrinology and Metabolism

Prolactinomas are the most common pituitary adenomas (approximately 40% of cases), and they represent an important cause of hypogonadism and infertility in both sexes. The magnitude of prolactin (PRL) elevation can be useful in determining the etiology of hyperprolactinemia. Indeed, PRL levels > 250 ng/mL are highly suggestive of the presence of a prolactinoma. In contrast, most patients with stalk dysfunction, drug-induced hyperprolactinemia or systemic diseases present with PRL levels < 100 ng/mL. However, exceptions to these rules are not rare. On the other hand, among patients with macroprolactinomas (MACs), artificially low PRL levels may result from the so-called "hook effect". Patients harboring cystic MACs may also present with a mild PRL elevation. The screening for macroprolactin is mostly indicated for asymptomatic patients and those with apparent idiopathic hyperprolactinemia. Dopamine agonists (DAs) are the treatment of choice for prolactinomas, particularly cabergoline, which is more effective and better tolerated than bromocriptine. After 2 years of successful treatment, DA withdrawal should be considered in all cases of microprolactinomas and in selected cases of MACs. In this publication, the goal of the Neuroendocrinology Department of the Brazilian Society of Endocrinology and Metabolism (SBEM) is to provide a review of the diagnosis and treatment of hyperprolactinemia and prolactinomas, emphasizing controversial issues regarding these topics. This review is based on data published in the literature and the authors' experience.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS, AMERICAN COLLEGE OF ENDOCRINOLOGY DISEASE STATE CLINICAL REVIEW: CLINICAL RELEVANCE OF MACROPROLACTIN IN THE ABSENCE OR PRESENCE OF TRUE HYPERPROLACTINEMIA

OBJECTIVE

To review the current literature regarding the prevalence of macroprolactin (macroPRL) in hyperprolactinemic patients and determine recommendations for testing.

METHODS

An electronic United States National Library of Medicine PubMed search (through October, 2014) was conducted for search term "macroprolactin." Only English-language articles were considered.

RESULTS

MacroPRL is an under-recognized cause of elevated prolactin (PRL) and is present in approximately 4% to 40% of hyperprolactinemic patients depending on the referral population. Clinical findings which could be due to hyperprolactinemia are the impetus for testing for PRL. Because of this there is significant overlap in the clinical presentation of patients with true hyperprolactinemia and those with macroPRL, differentiation cannot always be made on the basis of symptoms. A lack of recognition of the presence of macroPRL can lead to unnecessary laboratory investigations, imaging, and pharmacologic or surgical treatment.

CONCLUSION

Until there is a commercially available PRL assay that is not subject to interference by macroPRL, clinicians should consider the possibility of macroPRL, especially if the clinical presentation, imaging findings, and/or response to therapy reveal inconsistencies.

Chronic cluster headache and the pituitary gland

BACKGROUND

Cluster headache is classified as a primary headache by definition not caused by an underlying pathology. However, symptomatic cases of otherwise typical cluster headache have been reported.

CASE PRESENTATION

A 47-year-old male suffered from primary chronic cluster headache (CCH, ICHD-3 beta criteria fulfilled) since the age of 35 years. A magnetic resonance imaging (MRI) study of the brain in 2006 came back normal. He tried several prophylactic treatments but was never longer than 1 month without attacks. He was under chronic treatment with verapamil with only a limited effect on the attack frequency. Subcutaneous sumatriptan 6 mg injections were very effective in aborting attacks. By February 2014 the patient developed a continuous interictal pain ipsilateral to the right-sided cluster headache attacks. An indomethacin test (up to 225 mg/day orally) was negative. Because of the change in headache pattern we performed a new brain MRI, which showed a cystic structure in the pituitary gland. The differential diagnosis was between a Rathke cleft cyst and a cystic adenoma. Pituitary function tests showed an elevated serum prolactin level. A dopamine agonist (cabergoline) was started and the headache subsided completely. Potential pathophysiological mechanisms of pituitary tumor-associated headache are discussed.

CONCLUSION

Neuroimaging should be considered in all patients with CCH, especially those with an atypical presentation or evolution. Response to acute treatment does not exclude a secondary form of cluster headache. There may be shared pathophysiological mechanisms of primary and secondary cluster headache.

Coexistence of macroprolactinaemia and hyperprolactinaemia in women with oligo-/amenorrhoea is associated with high risk of pituitary adenomas

Macroprolactin may cause elevation of prolactin (PRL) concentrations measured by standard assays. In our study, we assessed the prevalence of pituitary lesions in women with macroprolactinaemia and either oligomenorrhoea or secondary amenorrhoea. Pituitary MRI scans were performed in 61 women aged 31.0  ±  6.7 years (mean  ±  SD), with raised PRL concentrations due to macroprolactinaemia, detected by 25% polyethylene glycol (PEG) precipitation method (PRL recovery <40%). After PEG precipitation of macroprolactin, free PRL concentrations were still raised in 36 (59%) women. Microadenomas were detected in 10 patients out of 61 (16.4%), with raised free PRL in 9 of these cases, while macroadenomas were detected in 4 out of 61 (6.6%) women, all of whom also had raised free PRL. In case of coexistence of macroprolactinaemia and raised free PRL after PEG precipitation of macroprolactin, the chance of finding of either a micro- or a macroadenoma was 36% (13 cases out of 36). We conclude that hyperprolactinaemia and macroprolactinaemia may coexist in the same patient. Furthermore, if free PRL is raised after PEG precipitation of macroprolactin, then the chance of finding either a pituitary micro- or macroadenoma in women with oligo-/amenorrhoea is over 30%. Therefore pituitary magnetic resonance imaging is mandatory in all such cases.

Serum prolactin and macroprolactin levels among outpatients with major depressive disorder following the administration of selective serotonin-reuptake inhibitors: a cross-sectional pilot study

Clinical trials evaluating the rate of short-term selective serotonin-reuptake inhibitor (SSRI)-induced hyperprolactinemia have produced conflicting results. Thus, the aim of this study was to clarify whether SSRI therapy can induce hyperprolactinemia and macroprolactinemia. Fifty-five patients with major depressive disorder (MDD) were enrolled in this study. Serum prolactin and macroprolactin levels were measured at a single time point (i.e., in a cross-sectional design). All patients had received SSRI monotherapy (escitalopram, paroxetine, or sertraline) for a mean of 14.75 months. Their mean prolactin level was 15.26 ng/ml. The prevalence of patients with hyperprolactinemia was 10.9% for 6/55, while that of patients with macroprolactinemia was 3.6% for 2/55. The mean prolactin levels were 51.36 and 10.84 ng/ml among those with hyperprolactinemia and a normal prolactin level, respectively. The prolactin level and prevalence of hyperprolactinemia did not differ significantly within each SSRI group. Correlation analysis revealed that there was no correlation between the dosage of each SSRI and prolactin level. These findings suggest that SSRI therapy can induce hyperprolactinemia in patients with MDD. Clinicians should measure and monitor serum prolactin levels, even when both SSRIs and antipsychotics are administered.

Determination of prolactin: the macroprolactin problem

Serum prolactin is frequently measured when investigating patients with reproductive disorders and elevated concentrations are found in up to 17% of such cases. Clinical laboratories rely predominantly on automated analysers to quantify prolactin levels using sandwich immunometric methodologies. Though generally robust and reliable, such immunoassays are susceptible to interference from a high molecular mass prolactin/IgG autoantibody complex termed macroprolactin. While macroprolactin remains reactive to varying degrees in all prolactin immunoassays, it exhibits little if any biological activity in vivo and consequently its presence is considered clinically irrelevant. Macroprolactinaemia, defined as hyperprolactinaemia due to excess macroprolactin with normal concentrations of bioactive monomeric prolactin, may lead to misdiagnosis and mismanagement of hyperprolactinemic patients if not recognised. Current best practice recommends that all sera with elevated total prolactin concentrations are sub-fractionated using polyethylene glycol precipitation to provide a more meaningful clinical measurement of the bioactive monomeric prolactin content. Manufacturers of prolactin assays should strive to minimise interference from macroprolactin in their assays. Clinical laboratories should introduce screening procedures to exclude macroprolactinaemia in all patients identified as having hyperprolactinaemia. Clinicians should be aware of this potential diagnostic pit fall and insist on PEG screening of all hyperprolactinaemic sera.

Frequency of Macroprolactinemia in Hyperprolactinemic Women Presenting with Menstrual Irregularities, Galactorrhea, and/or Infertility: Etiology and Clinical Manifestations

Aim. To determine the frequency of macroprolactinemia, its etiology, and the clinical manifestations in patients with hyperprolactinemia presenting with menstrual irregularities, galactorrhea, and/or infertility who were attended by the gynecology-endocrinology service. Methods. In a cross-sectional study, 326 hyperprolactinemic women were tested for serum prolactin (PRL) concentrations before and after chromatographic separation (gel filtration and affinity with protein G) and extraction of free PRL with polyethylene glycol (PEG). Results. Sera from 57 patients (17.5%) were found to have macroprolactinemia. The presence of macroprolactinemia was attributable to anti-PRL autoantibodies in 54 (94.7%) patients. The median serum PRL levels were similar in patients with or without macroprolactinemia (42.0 versus 38.1 ng/mL). In contrast, patients with macroprolactinemia had lower serum-free PRL levels (median 9.2 versus 31.7 ng/mL, P < 0.001). Patients without macroprolactinemia had a higher frequency of galactorrhea and abnormal pituitary imagine findings (P < 0.002). Conclusions. We can conclude that macroprolactinemia should be considered as a benign variant, and it must be ruled out in women presenting with menstrual irregularities, galactorrhea, and/or infertility in order to investigate other causes different than hyperprolactinemia. Serum PRL precipitated with PEG is a convenient and simple procedure to screen for the presence of macroprolactinemia.

Macroprolactinemia: new insights in hyperprolactinemia

Hypersecretion of prolactin by lactotroph cells of the anterior pituitary may lead to hyperprolactinemia in physiological, pathological and idiopathic conditions. Most patients with idiopathic hyperprolactinemia may have radiologically undetected microprolactinomas, but some may present other causes of hyperprolactinemia described as macroprolactinemia. This condition corresponds to the predominance of higher molecular mass prolactin forms (big-big prolactin, MW > 150 kDa), that have been postulated to represent prolactin monomer complexed with anti-prolactin immunoglobulins or autoantibodies. The prevalence of macroprolactinemia in hyperprolactinemic populations between 15–46% has been reported. In the pathophysiology of macroprolactinemia it seems that pituitary prolactin has antigenicity, leading to the production of anti-prolactin autoantibodies, and these antibodies reduce prolactin bioactivity and delay prolactin clearance. Antibody-bound prolactin is big enough to be confined to vascular spaces, and therefore macroprolactinemia develops due to the delayed clearance of prolactin rather than increased production. Although the clinical symptoms are less frequent in macroprolactinemic patients, they could not be diff erentiated from true hyperprolactinemic patients, on the basis of clinical features alone. Although gel filtration chromatography (GFC) is known to be the gold standard for detecting macroprolactin, the polyethylene glycol precipitation (PEG) method has off ered a simple, cheap, and highly suitable alternative. In conclusion, macroprolactinemia can be considered a benign condition with low incidence of clinical symptoms and therefore hormonal and imaging investigations as well as medical or surgical treatment and prolonged follow-up are not necessary.

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.

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.

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.

Detection of Macroprolactinemia and Molecular Characterization of Prolactin Isoforms in Blood Samples of Hyperprolactinemic Women

Prolactin (PRL) circulates in the blood in the form of monomeric prolactin, dimeric prolactin and macroprolactin. Macroprolactin is a common cause of hyperprolactinemia. The objective of this study was to assess the prevalence of macroprolactinemia in hyperprolactinemic women and to undertake the biochemical characterization of macroprolactin. A retrospective cross-sectional study was conducted on one hundred hyperprolactinemic patients. All the sera were subjected to polyethylene glycol (PEG) precipitation and were divided into true hyperprolactinemics (PRL recovery >60%), probable macroprolactinemics (PRL recovery between 40 and 60%) and macroprolactinemics (PRL recovery < 40%). The prevalence of macroprolactinemia was found to be 34%. Sera from each group were further analyzed for isoforms of prolactin by gel filtration chromatography (GFC). The clinical spectrum of presenting complaints in the hyperprolactinemic cohort included oligomenorrhea, galactorrhea and infertility, but the presentation did not differ between macroprolactinemic and truly hyperprolactinemic patients. GFC showed three major PRL isoforms, viz., 23.5 kDa (monomeric), 47 kDa (dimeric) and 150-174.6 kDa (PRL-IgG complexes) along with the medium and heavy weight aggregates of prolactin. The results of the study showed that macroprolactinemia is one of the causes of hyperprolactinemia with high prevalence. It is recommended that all hyperprolactinemic patients be screened for macroprolactinemia.

Clinical characterization of patients with macroprolactinemia and monomeric hyperprolactinemia

Macroprolactinemia is often a cause of misdiagnosis, unnecessary expensive investigation, and unsuitable treatment. The aim of the present study was to investigate the clinical findings and the concentrations of macroprolactin in patients with hyperprolactinemia in our region. Eighty-four female hyperprolactinemic patients were screened for macroprolactinemia. Prolactin was measured by chemiluminescence method on an Immulite 2000 analyzer (Siemens Health Diagnostics, Deerfield, IL, USA). Recoveries less than or equal to 40% after polyethylene glycol precipitation were indicative of macroprolactinemia. Clinical features and biochemical values were compared in true hyperprolactinemic and macroprolactinemic patients. Macroprolactinemia was detected in 31 patients (36.9%), with 84 hyperprolactinemic female patients. There was no difference in frequency of galactorrhea and oligomenorrhea/amenorrhea between the two groups. When we evaluated the clinical features of patients according to prolactin levels, no significant difference was found between the groups. In conclusion, our initial data show that no clinical features could reliably differentiate macroprolactinemic from true hyperprolactinemic patients, but at least one of these symptoms was present in most macroprolactinemic patients.

Treatment for prolactinomas and hyperprolactinaemia: a lifetime approach

BACKGROUND

Prolactinomas are the most common hormone-secreting pituitary tumours and are amenable to medical therapy with dopamine agonists. Indication for treatment will most commonly result from hypogonadism, infertility or symptoms related to tumour size. Thus, both diagnosis and treatment will essentially depend on the patients' stage of life, namely prepubertal, reproductive or postreproductive stage. This review will focus on a lifespan-dependent diagnosis and treatment for prolactinoma and hyperprolactinaemia.

METHODS

PubMed, the Cochrane Library, the Web of Science and EMBASE were searched electronically. No restriction was made with respect to language. Relevant current articles will be included in this review.

RESULTS

Prevalence of prolactinomas and clinical symptoms are age group-specific, and treatment of first choice is dopamine agonists over the whole lifespan. Open questions in the treatment for hyperprolactinaemia include optimal choice and duration of pharmacological treatment. In addition, concerns have been raised on the safety of dopamine agonists since a reported association of valvular heart disease with dopaminergic treatment in patients with Parkinson's disease.

CONCLUSIONS

Clinical presentation and consequences of hyperprolactinaemia and prolactinoma will differ in the specific stages of reproductive life and require an adequate lifetime-dependent diagnostic and therapeutic approach.

Macroprolactinemia, like hyperprolactinemia, may promote platelet activation

Insulin resistance, which provides a convenient milieu for platelet activation, has been closely associated with atherosclerotic disorders. Although it often accompanies hyperprolactinemia, findings conflict concerning its clinical impact in macroprolactinemia. In order to investigate the relationship between hyperprolactinemia and platelet activation evidenced by ADP-stimulated P-selectin expression on flow cytometry, we studied hyperprolactinemic, macroprolactinemic, and normoprolactinemic subjects. Thirty-four hyperprolactinemic and 44 age- and body mass index-matched euprolactinemic premenopausal women were included. They were matched regarding insulin sensitivity status, waist circumference, blood pressures, and plasma lipids. In order to detect macroprolactinemia among hyperprolactinemic cases, prolactin was measured before and after polyethylene glycol (PEG) precipitation in patients' sera. P-selectin expression was significantly higher in the hyperprolactinemic group (P =0.001), and 41.2% of them exhibited macroprolactinemia. Expression of P-selectin was comparable between the macroprolactin-negative (monomeric hyperprolactinemia; n = 20) and -positive (n = 14) subgroups (P = 0.90). Both subgroups showed greater expression compared with normoprolactinemic controls (P = 0.014 and 0.005, respectively). Platelet activation accompanies the atherosclerotic disorders closely associated with insulin resistance. Among groups matched with regard to insulin-sensitivity markers, both monomeric hyperprolactinemia and macroprolactinemia appeared to promote platelet activation.

Comparison of multiple methods for identification of hyperprolactinemia in the presence of macroprolactin

BACKGROUND

Macroprolactin is a large, heterogeneous form of prolactin with limited bioavailability. Detection of macroprolactin by different immunoassays varies widely. The objectives of this study were to determine the immunoreactivity of macroprolactin by the Ortho Clinical Diagnostics Vitros((R)) ECi prolactin immunoassay, establish the most effective method for interpreting the prolactin concentration after PEG-precipitation, and correlate the clinical features of hyperprolactinemia with the presence of macroprolactin.

METHODS

PEG-precipitation was performed on 120 hyperprolactinemic specimens. Of these, 31 specimens with a recovery<80% were fractionated by GFC. Four different approaches for identifying true hyperprolactinemia were investigated. Clinical symptoms of hyperprolactinemia were determined by chart review.

RESULTS

Macroprolactin was detected by the Vitros ECi prolactin immunoassay. Use of a PEG modified prolactin reference interval was effective for identifying hyperprolactinemia in the presence of macroprolactin. There was no difference in the prevalence of abnormal menses, galactorrhea, or abnormal MRI between those with and without macroprolactin (p>0.05). Accounting for macroprolactin in patients with hyperprolactinemia reduced the number of idiopathic cases.

CONCLUSIONS

The Vitros ECi prolactin immunoassay detects macroprolactin. PEG-precipitation is an acceptable surrogate to detect hyperprolactinemia in the presence of macroprolactin when using a prolactin reference interval derived from PEG precipitated reference sera. Although testing for macroprolactin should not substitute for standard evaluation of hyperprolactinemia, identification of macroprolactin may clarify a diagnosis and direct appropriate therapy.

The effect of identifying macroprolactinemia on health-care utilization and costs in patients with elevated serum prolactin levels

OBJECTIVES

The routine screening for macroprolactin of all hyperprolactinemic patients may avoid unnecessary imaging procedures and medication prescription. The study described the frequency and types of tests requested after a diagnosis of high serum prolactin concentration, and assessed whether the diagnosis of macroprolactinemia resulted in lower downstream utilization and costs compared with hyperprolactinemic patients.

METHODS

A cost analysis was conducted using a decision tree to model the health-care utilization of the two groups. The database of the Fleury Medicina e Saúde provided the tests and medication of patients with a prolactin value >or=30 microg/L for a period of 6 months.

RESULTS

Six hundred fifty-four of 1793 patients (36.5%) had hyperprolactinemia because of macroprolactin. The average number of tests per individual was higher (P = 0.001) in the patients with true hyperprolactinemia (3.07) than in patients with macroprolactinemia (2.51).The average cost in the hyperprolactinemic group (R$425 or euro 162) was significantly higher (P < 0.001) than the macroprolactinemic group (R$340 or euro 130), an incremental cost 25% higher.

CONCLUSION

The macroprolactin screening did not completely avoid inappropriate clinical investigation or associated health-care costs. Our results demonstrate the importance of proper medical education and knowledge diffusion of the meaning of macroprolactinemia.

Diagnosis and management of hyperprolactinemia: results of a Brazilian multicenter study with 1234 patients

OBJECTIVE

The aim of the study was to evaluate clinical and laboratorial features of 1234 patients with different etiologies of hyperprolactinemia, as well as the response of 388 patients with prolactinomas to dopamine agonists.

DESIGN, SETTING, AND PATIENTS

A total of 1234 hyperprolactinemic patients from 10 Brazilian endocrine centers were enrolled in this retrospective study.

MAIN OUTCOME MEASURE

PRL measurement, thyroid function tests, and screening for macroprolactin were conducted.

RESULTS

Patients were subdivided as follows: 56.2% had prolactinomas, 14.5% drug-induced hyperprolactinemia, 9.3% macroprolactinemia, 6.6% non-functioning pituitary adenomas, 6.3% primary hypothyroidism, 3.6% idiopathic hyperprolactinemia, and 3.2% acromegaly. Clinical manifestations were similar irrespective of the etiology of the hyperprolactinemia. The highest PRL levels were observed in patients with prolactinomas but there was a great overlap in PRL values between all groups. However, PRL>500 ng/ml allowed a clear distinction between prolactinomas and the other etiologies. Cabergoline (CAB) was more effective than bromocriptine (BCR) in normalizing PRL levels (81.9% vs 67.1%, p<0.0001) and in inducing significant tumor shrinkage and complete disappearance of tumor mass. Drug resistance was observed in 10% of patients treated with CAB and in 18.4% of those that used BCR (p=0.0006). Side-effects and intolerance were also more common in BCR treated patients.

CONCLUSION

Prolactinomas, drug induced hyperprolactinemia, and macroprolactinemia were the 3 most common causes of hyperprolactinemia. Although PRL levels could not reliably define the etiology of hyperprolactinemia, PRL values >500 ng/ml were exclusively seen in patients with prolactinomas. CAB was significantly more effective than BCR in terms of prolactin normalization, tumor shrinkage, and tolerability.

Hyperprolactinemia and prolactinomas

Any process interfering with dopamine synthesis, its transport to the pituitary gland, or its action at the level of lactotroph dopamine receptors can cause hyperprolactinemia. As described in this article, considering the complexity of prolactin regulation, many factors could cause hyperprolactinemia, and hyperprolactinemia can have clinical effects not only on the reproductive axis. Once any drug effects are excluded, prolactinomas are the most common cause of hyperprolactinemia. The most frequent symptom is hypogonadism in both genders. Medical and surgical therapies generally have excellent results, and most prolactinomas are well controlled or even cured in some cases.

Patients with macroprolactinaemia: clinical and radiological features

BACKGROUND

Macroprolactinaemia may represent a relevant cause of misdiagnosis, unnecessary investigation and inappropriate treatment. The aim of this study was to investigate the clinical and neuroradiological characteristics of patients with and without macroprolactinaemia and to evaluate the impact of macroprolactin determination on the diagnostic work-up of hyperprolactinaemic patients.

MATERIALS AND METHODS

Retrospective analysis in 135 consecutive hyperprolactinaemic patients (111 women and 24 men; mean age 37 +/- 11.6 years) whose archived sera were subsequently tested for macroprolactin. Recoveries </= 40% after polyethylene glycol precipitation were indicative of macroprolactinaemia.

RESULTS

Macroprolactin, entirely explaining biochemical hyperprolactinaemia, was found in 42.2% of patients, a third of whom presented with signs and symptoms of hyperprolactinaemia. Determination of macroprolactin changed the initial diagnosis in a consistent proportion of patients. In particular, idiopathic hyperprolactinaemia, initially diagnosed in 41 patients, was then excluded in 28 of them. Diagnosis of prolactin-secreting pituitary microadenoma shifted to non-secreting pituitary microadenoma in 10 of 49 patients, while in all patients with prolactin-secreting pituitary macroadenoma or hyperprolactinaemia due to stalk deafferentation the presence of macroprolactin was excluded and the initial diagnosis confirmed. Finally, macroprolactin was present in the majority of patients with magnetic resonance imaging (MRI) scans suggestive for primary empty sella (4 of 5 women) or pituitary hyperplasia (12 of 17 women, 3 of 3 men). Collectively, about half of subjects with macroprolactinaemia showed variable MRI abnormalities.

CONCLUSIONS

The presence of macroprolactin was a relevant cause of misdiagnosis in patients with hyperprolactinaemia. However, due to the unexpected high frequency of pituitary abnormalities observed in the present series, we suggest that the diagnostic algorithm of hyperprolactinaemic states should include both polyethylene glycol precipitation test and MRI imaging.

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.

Prevalência da macroprolactinemia entre 115 pacientes com hiperprolactinemia

Macroprolactinemia caracteriza-se pelo predomínio no soro de uma prolactina (PRL) de alto peso molecular e baixa atividade biológica que não requer tratamento. A prevalência de macroprolactinemia foi avaliada em 115 pacientes consecutivos com hiperprolactinemia. Entre eles, 19 (16,5%) tinham exclusivamente macroprolactinemia, 4 (3,5%) síndrome dos ovários policísticos, 7 (6,1%) acromegalia, 8 (6,9%) hiperprolactinemia idiopática, 10 (8,7%) hipotiroidismo primário, 14 (12,2%) adenomas clinicamente não-funcionantes, 20 (17,4%) hiperprolactinemia farmacológica e 33 (28,7%) prolactinomas. O diagnóstico de macroprolactinemia foi estabelecido pela obtenção de uma recuperação da PRL < 30% após tratamento do soro com polietilenoglicol. Dentre os 19 pacientes com macroprolactinemia isolada, 16 (84,2%) eram mulheres e 12 (63,2%) eram assintomáticos, enquanto 4 (21%) tinham oligomenorréia e 3 (15,8%), galactorréia. Em contraste, apenas 11,5% dos indivíduos com outras causas de hiperprolactinemia eram assintomáticos (p< 0,001). Os níveis de PRL nos casos de macroprolactinemia variaram de 45,1 a 404 ng/mL (média de 113,3 ± 94,5), mas em 15 (78,9%) foram < 100 ng/mL. Nossos achados demonstram que macroprolactinemia é uma condição freqüente e, assim, sugerimos que seja rotineiramente pesquisada em pacientes com hiperprolactinemia.

Macroprolactin, big-prolactin and potential effects on the misdiagnosis of hyperprolactinemia using the Beckman Coulter Access Prolactin assay

OBJECTIVE

To examine whether use of the Beckman Coulter Access Prolactin (PRL) assay, which has low reactivity with macro-PRL, obviates the need for screening hyperprolactinemic samples.

DESIGN AND METHODS

Samples from 1020 hyperprolactinemic individuals and 401 healthy volunteers were treated with polyethylene glycol (PEG). Macro-PRL was assessed from (1) percent PRL recovery, using cut-off values derived by gel filtration chromatography (GFC) and (2) significant (p<0.05) normalisation of PRL following PEG.

RESULTS

PRL recovery was similar in volunteer and hyperprolactinemic samples (mean+/-SD 101+/-13% and 101+/-19%, respectively). In hyperprolactinemic samples, macro-PRL was identified from PRL recovery in 9.7%, although levels were moderate to high in only 3.9%. The total PRL normalised following PEG in 7.4%. Correlations of PRL recovery with the proportions of macro-, big- and monomeric PRL following GFC (n=30 samples, range of PRL and macro-PRL levels) were -0.89, -0.20 and 0.92, respectively. The big-PRL content was 0-28%. Regression analysis suggested that PEG precipitated both macro-PRL and big-PRL.

CONCLUSIONS

Using the Access assay, macro-PRL can cause apparent hyperprolactinemia and big-PRL may cause misclassification of individuals. Screening using PEG is applicable to assays with low macro-PRL reactivity provided specific reference values are derived.

Incidence and clinical significance of elevated macroprolactin levels in patients with hyperprolactinemia

OBJECTIVE

To determine the prevalence and clinical characteristics of patients with macroprolactinemia in an endocrinology practice at a tertiary care military medical center in the United States.

METHODS

We reviewed the medical records of 40 patients who had been referred for evaluation of hyper-prolactinemia between June 2003 and August 2004 in whom macroprolactin had been measured.

RESULTS

Of the 40 patients, 18 (9 men and 9 women) (45%) had an elevated macroprolactin level (mean, 75% of the total prolactin). The demographic characteristics of these patients were similar to those of patients with elevated monomeric prolactin. Most of the men with macro-prolactinemia (78%) had erectile dysfunction as the presenting complaint, whereas the most frequent symptom in women was menstrual irregularities (56%). Fifty percent of patients had no identifiable cause for their presenting complaint other than macroprolactinemia. Of the 18 patients with macroprolactinemia, 16 underwent magnetic resonance imaging (MRI) of the pituitary, of whom 56% had normal findings. Of the patients with abnormal MRI findings, 57% had a microadenoma, and 43% had either an atrophic anterior lobe or a prominent hypophysis. No significant relationship was detected between MRI findings or symptoms and the presence of elevated macroprolactin levels. Approximately 40% of patients in the macroprolactin group were treated with a dopamine agonist, 28% of whom had normalization of the total prolactin level.

CONCLUSION

Although macroprolactin is commonly found in patients with hyperprolactinemia, neither symptoms nor MRI findings are useful in predicting its presence. Patients with macroprolactinemia often have symptoms similar to those in patients with elevation in monomeric prolactin. The clinical significance of macro-prolactinemia remains uncertain.

Guidelines of the Pituitary Society for the diagnosis and management of prolactinomas

In June 2005, an ad hoc Expert Committee formed by the Pituitary Society convened during the 9th International Pituitary Congress in San Diego, California. Members of this committee consisted of invited international experts in the field, and included endocrinologists and neurosurgeons with recognized expertise in the management of prolactinomas. Discussions were held that included all interested participants to the Congress and resulted in formulation of these guidelines, which represent the current recommendations on the diagnosis and management of prolactinomas based upon comprehensive analysis and synthesis of all available data.

Pituitary imaging is indicated for the evaluation of hyperprolactinemia

OBJECTIVE

To evaluate the signs and symptoms associated with hyperprolactinemia and establish guidelines for a minimal serum PRL level for which pituitary imaging is indicated.

DESIGN

Retrospective study.

SETTING

Reproductive endocrinology clinic in a university hospital.

PATIENT(S)

One hundred four consecutive patients with hyperprolactinemia, mean age 30 +/- 6.5 (range 19-44) years.

INTERVENTION(S)

Classification of clinical symptoms, serum hormone measurements, and pituitary magnetic resonance imaging (MRI).

MAIN OUTCOME MEASURE(S)

Incidence of presenting symptoms, serum PRL levels, and pituitary tumor size.

RESULT(S)

Median (range) PRL value was 82.6 ng/mL (25-1,342). Reported symptoms from most to least common were infertility (48%), headaches (39%), oligoamenorrhea (29%), galactorrhea (24%), and visual changes (13%). Hypothyroidism was diagnosed in 2 of 104 (1.9%) patients. Of 86 patients who had pituitary imaging, 23 (26%) had normal findings and 63 (74%) had pituitary tumor; of these, 47 (55% of total imaged) had microadenomas and 16 (19% of total imaged) had macroadenomas. There was a statistically significant association between the tumor size and the PRL level. However, 11% of the patients with microadenomas had PRL levels >200 ng/mL, and 44% of the patients with macroadenomas had PRL levels between 25 and 200 ng/mL.

CONCLUSION(S)

The most common symptoms in the population studied were infertility and headaches. Coexisting thyroid disease was an uncommon finding. Most patients had a pituitary tumor on MRI. Although tumor size correlated with the serum PRL level, some macroadenomas were detected in women with only moderately elevated PRL values. On the basis of these findings, pituitary imaging should be obtained to identify pituitary tumors in all patients with persistently elevated PRL levels.

Endocrine causes of erectile dysfunction

Erectile dysfunction (ED) is one of the commonest disorders of male sexual function. Penile erection depends on a complex interaction of psychological, neural, vascular and endocrine factors. Testosterone has an important role in both central and peripheral domains of this process. In this article we discuss the role of testosterone in male sexual function and endocrine causes of ED.

The impact on clinical practice of routine screening for macroprolactin

BACKGROUND

Macroprolactin has reduced bioactivity in vivo and accumulates in the sera of some subjects, resulting in pseudo-hyperprolactinemia and consequent misdiagnosis.

METHODS

We have audited our experience of routine screening for macroprolactin using polyethylene glycol (PEG) precipitation over a 5-yr period in a single center.

RESULTS

Application of a reference range for monomeric prolactin (the residual prolactin present in macroprolactin-depleted serum) for normal individuals revealed that 453 of 2089 hyperprolactinemic samples (22%) identified by Delfia immunoassay were explained entirely by macroprolactin. The percentage of hyperprolactinemic samples explained by macroprolactinemia was similar across all levels of total prolactin (18, 21, 19, and 17% of samples from 700-1000, 1000-2000, 2000-3000, and greater than 3000 mU/liter, respectively). Application of an absolute prolactin threshold after polyethylene glycol treatment of sera, rather than the traditional method, i.e. less than 40% recovery, minimizes the opportunity for misclassification of patients in whom macroprolactin accounted for more than 60% of prolactin and the residual bioactive prolactin was present in excess. Macroprolactinemic patients could not be differentiated from true hyperprolactinemic patients on the basis of clinical features alone. Although oligomenorrhea/amenorrhea and galactorrhea were more common in patients with true hyperprolactinemia (P < 0.05), they were also frequently present in macroprolactinemic patients. Plasma levels of estradiol and LH and the LH/FSH ratio were significantly greater in macroprolactinemic compared with true hyperprolactinemic subjects (P < 0.05). Reduced use of imaging and dopamine agonist treatment resulted in a net cost savings, offsetting the additional cost associated with the introduction of screening.

CONCLUSION

Routine screening of all hyperprolactinemic sera for macroprolactin is recommended.

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.

Hyperprolactinaemia and the regular menstrual cycle in asymptomatic women: should it be treated during therapy for infertility?

It is known that hyperprolactinaemia can cause galactorrhoea and irregular cycles or even amenorrhoea. High serum prolactin (PRL) can disturb follicular maturation and corpus luteum function. Treatment of hyperprolactinaemia in patients with resulting bleeding anomalies is established, but the question is how to manage normal cyclic hyperprolactinaemic women? Studies have shown that in a subgroup of asymptomatic patients the serum contains mainly high molecular weight form (big big PRL), which has a low bioactivity, called macroprolactinaemia. It is evident that macroprolactin does not affect the control of pituitary PRL secretion via the short loop feedback mechanism or the secretion of gonadotrophins as does monomeric PRL. Identification of macroprolactinaemia is therefore clinically important to prevent unnecessary examinations and inappropriate treatment. Prolactinoma can be associated with macroprolactinaemia. Performance of pituitary imaging in asymptomatic patients with hyperprolactinaemia may therefore be justified, but further studies are needed to evaluate the relation of costs and benefit. An unsolved problem is the differentiation between inactive and PRL-secreting tumours. Caution should be exercised concerning medical treatment in unstimulated patients and also in patients during ovarian stimulation alone or in combination with intrauterine insemination or in-vitro fertilization. The potential clinical significance of hyperprolactinaemia/macroprolactinaemia in asymptomatic women must be further evaluated.

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.

Frequent misdiagnosis and mismanagement of hyperprolactinemic patients before the introduction of macroprolactin screening: application of a new strict laboratory definition of macroprolactinemia

BACKGROUND

Macroprolactin (big big prolactin) has reduced bioactivity and is measured by immunoassays for prolactin when it accumulates in the plasma of some individuals. We applied normative data for serum prolactin after treatment of sera to remove macroprolactin to elucidate the contribution of macroprolactin to misleading diagnoses, inappropriate investigations, and unnecessary treatment.

METHODS

We reviewed records of women attending a tertiary referral center who had prolactin >1000 mIU/L. Application of a reference interval to polyethylene glycol (PEG)-treated hyperprolactinemic sera identified 21 patients in whom hyperprolactinemia was accounted for entirely by the presence of macroprolactin. Presenting clinical features, diagnoses, and treatment were compared in these patients and 42 age-matched true hyperprolactinemic patients.

RESULTS

Prolactin concentrations in sera of 110 healthy individuals ranged from 78 to 564 mIU/L. The range of values for the sera after PEG treatment was 70-403 mIU/L. For macroprolactinemic samples, PEG treatment decreased mean (SD) prolactin from 1524 (202) mIU/L to 202 (27) mIU/L but decreased it only from 2096 (233) mIU/L to 1705 (190) mIU/L in true hyperprolactinemic patients (P <0.01 between groups). Oligomenorrhea or amenorrhea and galactorrhea were the most common clinical features in both groups, although they occurred more frequently in true hyperprolactinemic patients (P <0.05). Serum estradiol and luteinizing hormone concentrations were significantly higher in participants with macroprolactinemia than in those with true hyperprolactinemia (P <0.05). Among participants with retrospectively identified macroprolactinemia, pituitary imaging was performed in 93% and treatment with dopamine agonist was prescribed in 87%.

CONCLUSIONS

Macroprolactin is a significant cause of misdiagnosis, unnecessary investigation, and inappropriate treatment. The use of an appropriate reference interval for the PEG immunoprecipitation procedure may be of particular importance in those patients who have an excess of both macroprolactin and monomeric prolactin.

Clinical and radiological features of patients with macroprolactinaemia

OBJECTIVES

Macroprolactin is a complex of prolactin (PRL) and IgG and may account for a significant proportion of cases of 'idiopathic hyperprolactinaemia'. In this study, we sought to determine the prevalence and clinical features of macroprolactinaemia in patients diagnosed with hyperprolactinaemia in our region, with a view to determining how patients with macroprolactinaemia should be investigated and managed.

PATIENTS AND METHODS

An Immuno-1 automated immunoassay system with polyethylene glycol (PEG) precipitation was used to identify macroprolactin, with a recovery of </= 50% taken as indicating significant macroprolactinaemia. Macroprolactin was found in 58 (21%) of 273 patients with a total PRL > 700 mU/l. The clinical records of 51 (44 female) were available for retrospective review.

RESULTS

The mean (range) age of patients was 39.5 (18-82) years. The median (range) concentrations for the various forms of PRL were: total PRL 1130 mU/l (728-5116), monomeric PRL 240 mU/l (50-656) and macroprolactin 895 mU/l (381-4854). Classical symptoms of hyperprolactinaemia were present in 39% of patients, although in many there were other possible explanations for their symptomatology. Pituitary adenomas were identified in six out of 36 people who underwent neuroimaging. Five of these patients had a microadenoma and one had a 10-mm macroadenoma (although, in this patient macroprolactin was identified after the discovery of the tumour). There was no relationship between macroprolactin concentrations and the presence of hyperprolactinaemic symptoms or neuroimaging abnormalities.

CONCLUSIONS

Macroprolactinaemia is a common occurrence in patients with hyperprolactinaemia, but associated symptomatology may not necessarily be linked. The neuroimaging abnormalities were also probably incidental findings and it is questionable whether neuroimaging is necessary when significant macroprolactinaemia is identified and the concentration of monomeric PRL is not elevated (using the Immuno-1 assay system, following PEG precipitation).

Armadilhas no diagnóstico da hiperprolactinemia

Na abordagem diagnóstica da hiperprolactinemia, três armadilhas ou problemas potenciais merecem uma atenção especial: os incidentalomas hipofisários (presentes em 10% da população adulta à ressonância magnética), o efeito gancho e a macroprolactinemia. O efeito gancho se caracteriza pela presença de níveis falsamente baixos de prolactina (PRL), quando se empregam imunoensaios de dois sítios em pacientes com grandes prolactinomas e hiperprolactinemia muito acentuada. O efeito gancho pode ser identificado através de uma nova dosagem da PRL após diluição do soro a 1:100, quando se observará um aumento dramático do valor da PRL. Ele deve ser excluído em qualquer paciente com um macroadenoma e níveis séricos de PRL <200ng/mL. A macroprolactinemia responde por cerca de 10% dos casos de hiperprolactinemia. Resulta de um excesso de PRL polimérica (macroprolactina ou big big prolactin), cuja biodisponibilidade é diminuída. Assim, a maioria dos pacientes com macroprolactinemia não apresenta os sintomas clássicos da hiperprolactinemia e habitualmente não requerem tratamento.