Serum prolactin revisited: parametric reference intervals and cross platform evaluation of polyethylene glycol precipitation-based methods for discrimination between hyperprolactinemia and macroprolactinemia

The research trend of hyperprolactinemia from 2011 to 2023 was analyzed by bibliometrics

The objective of this study is to conduct a bibliometric analysis of research trends in hyperprolactinemia from 2011 to 2023. This analysis aims to provide researchers with insights into the current hotspots and frontiers related to hyperprolactinemia. It is worth noting that there are currently no existing reports on bibliometric analyses of hyperprolactinemia. The Social Science Citation Index (SSCI) and Science Citation Index Expanded (SCIE) databases of the Web of Science Core Collection were systematically searched for "articles" and "review articles" related to the topic of hyperprolactinemia from 2011 to 2023. VOSviewer was employed to conduct bibliometric analysis, aiming to analyze the research trends in hyperprolactinemia over the past 13 years. A total of 1865 eligible articles were retrieved, with contributions from 9544 scholars representing 83 countries in the field of research. The United States had the highest number of publications, followed by China. The keywords were categorized into six clusters: (1) etiology of hyperprolactinemia and other related endocrine and metabolic diseases. (2) Hyperprolactinemia and mental illness. (3) Diagnosis and management of hyperprolactinemia. (4) Treatment of hyperprolactinemia and prolactinoma. (5) Detection of macroprolactin and macroprolactinemia. (6) Symptoms of male hyperprolactinemia. Over the past 13 years, there has been a consistent and slightly increasing trend in the number of research papers focusing on hyperprolactinemia. The primary areas of research focus are centered around the diagnosis and treatment of hyperprolactinemia caused by antipsychotic drugs or prolactinoma.

Diagnosis and management of prolactin-secreting pituitary adenomas: a Pituitary Society international Consensus Statement

This Consensus Statement from an international, multidisciplinary workshop sponsored by the Pituitary Society offers evidence-based graded consensus recommendations and key summary points for clinical practice on the diagnosis and management of prolactinomas. Epidemiology and pathogenesis, clinical presentation of disordered pituitary hormone secretion, assessment of hyperprolactinaemia and biochemical evaluation, optimal use of imaging strategies and disease-related complications are addressed. In-depth discussions present the latest evidence on treatment of prolactinoma, including efficacy, adverse effects and options for withdrawal of dopamine agonist therapy, as well as indications for surgery, preoperative medical therapy and radiation therapy. Management of prolactinoma in special situations is discussed, including cystic lesions, mixed growth hormone-secreting and prolactin-secreting adenomas and giant and aggressive prolactinomas. Furthermore, considerations for pregnancy and fertility are outlined, as well as management of prolactinomas in children and adolescents, patients with an underlying psychiatric disorder, postmenopausal women, transgender individuals and patients with chronic kidney disease. The workshop concluded that, although treatment resistance is rare, there is a need for additional therapeutic options to address clinical challenges in treating these patients and a need to facilitate international registries to enable risk stratification and optimization of therapeutic strategies.

Unexplained Hyperthyrotropinemia: A Biochemical and Clinical Challenge

BACKGROUND

A raised serum TSH in the absence of a clear etiology, or "unexplained hyperthyrotropinemia" (UH), can be challenging for clinicians. The aim of the present study was to evaluate potential strategies aimed at a clinical and biochemical characterization of UH patients.

METHODS

We compared 36 patients with UH with a control group of 14 patients with chronic autoimmune thyroiditis (CAT) and subclinical hypothyroidism. The two groups were compared in terms of the following: (i) the rate of normalization of TSH after repeating with another assay; (ii) the rate of normalization of TSH over time with the same assay; (iii) the reduction in TSH after precipitation with polyethilenglycole (PEG); and (iv) free thyroxine (FT4) levels.

RESULTS

Similar TSH levels were observed in UH [5.65 (5.21-6.37)] and CAT [5.62 (5.17-8.50)] (p = 0.489). TSH measurement with another assay method showed a normal TSH value in 41.9% of UH vs. 46.1% of CAT patients (p = 0.797). After repeating the TSH measurement in time with the same assay method, an increased TSH value was confirmed in all cases, in both groups (0% in the UH group vs. 0% in the CAT group, p = 1.000). TSH recovery after PEG precipitation was similar in the two groups (% precipitable post-PEG: 68.75 ± 3.14 in UH vs. 68.67 ± 7.18 in CAT, p = 0.960). FT4 levels were similar in the two groups (FT4 1.02 ± 0.20 ng/dl in UH vs. 1.00 ± 0.20 ng/dl in CAT, p = 0.789).

CONCLUSIONS

The results do not support the concept that laboratory interferences are more frequent in UH patients, suggesting that patients with UH should be managed in the same way as patients with CAT until proven otherwise.

Reference intervals of the sex hormonal profile in healthy women: A retrospective single-center study in Peru

The female hormonal profile is of utmost importance for the assessment of the endocrinological functional status and the diagnosis of diseases. The analysis must delimit their normality intervals based on the manufacturer's cut-off points. Due to not all intervals can be evaluated before use, it is imperative to verify the reference intervals to achieve uniformity in the interpretation of results in the female population. We determine the reference intervals of five female sex hormones [Follicle Stimulating hormone (FSH), Estradiol, Luteinizing Hormone (LH), Prolactin, and progesterone] using electrochemiluminescence in the Cobas e411 (Roche). We included female patients >18 years old, between the 3rd and 15th day of the menstrual cycle (follicular phase) and had no previous medical history or recent medication. For reference intervals analysis, we followed the recommendations of the CLSI C28-A3 guideline. The average concentration for FSH, progesterone, LH, prolactin and estradiol were 11.48 ± 21.10 mIU/ml, 8.19 ± 11.90 ng/ml, 10.98 ± 11.55 ng/ml, 25.05 ± 32.74 ng/mL, and 147.08 ± 473.8 pmol/mL, respectively. Eighty per cent of parameters showed a satisfactory transfer for the manufacturer's reference intervals, except for estradiol, which had 85.5% of transferred values. Our results suggest that 4/5 sex hormones were found within the manufacturer's reference intervals and can be quantified in Peruvian women, ensuring the quality of their results. However, it is necessary to determine the estradiol with other reagents and assays since we show errors in the transfer of intervals.

Cross-reactivity in assays for prolactin and optimum screening policy for macroprolactinaemia

OBJECTIVES

Macroprolactin cross-reacts in immunoassays for prolactin causing apparent hyperprolactinaemia (macroprolactinaemia) and consequent misdiagnosis and mismanagement of patients.

METHODS

We determined the prevalence of macroprolactinaemia using prolactin immunoassays with reported "high" (Tosoh) or "low" cross-reactivity (Roche) with macroprolactin. We additionally modelled the effects of increasing the screening threshold on workload and sensitivity in the detection of macroprolactinaemia.

RESULTS

A review of routine requests for prolactin received in a 12 month period identified 670 sera with hyperprolactinaemia (Tosoh assay). Treatment with polyethylene glycol (PEG) precipitation demonstrated normal levels of monomeric prolactin in 165 sera (24.6%) indicating macroprolactinaemia. In the macroprolactinaemic cohort, total prolactin levels were lower with the Roche assay (473 ± 132 mU/L; mean ± SD) compared to the Tosoh assay (683 ± 217 mU/L), p < 0.005. The prevalence of macroprolactinaemia was also lower with the Roche assay (6.2%). The number of samples that required screening for macroprolactinaemia fell by 14% when Roche gender specific total prolactin reference limits were applied. Use of a higher screening threshold (700 mU/L) reduced the screening workload considerably (Roche by 45%, Tosoh by 37%) however, the sensitivity of detection of macroprolactinaemia decreased markedly (Roche 90%, Tosoh 59%).

CONCLUSIONS

Macroprolactin interferes in both Tosoh and Roche prolactin immunoassays. Use of an assay with a relatively low cross reactivity with macroprolactin, e.g. Roche, will lead to a modest reduction in the screening workload. Increasing the screening threshold above the upper limit of the assay reference interval will also reduce the screening workload but leads to disproportionate increases in the number of cases of macroprolactinaemia which are missed.

Interference by macroprolactin in assays for prolactin: will the In Vitro Diagnostics Regulation lead to a solution at last?

Cross reactivity with high molecular weight complexes of prolactin known as macroprolactin is a common cause of positive interference in assays for serum prolactin. All prolactin assays currently available are affected with 5-25% of results indicating hyperprolactinaemia falsely elevated due to macroprolactinaemia - hyperprolactinaemia due to macroprolactin with normal concentrations of bioactive monomeric prolactin. Macroprolactinaemia has no pathological significance but, if it is not recognised as the cause, the apparent hyperprolactinaemia can lead to clinical confusion, unnecessary further investigations, inappropriate treatment and waste of healthcare resources. Macroprolactinaemia cannot be distinguished from true hyperprolactinaemia on clinical grounds alone but can be detected by a simple laboratory test based on the precipitation of macroprolactin with polyethylene glycol. Laboratory screening of all cases of hyperprolactinaemia to exclude macroprolactinaemia has been advised as best practice but has not been implemented universally and reports of clinical confusion caused by macroprolactinaemia continue to appear in the literature. Information provided by manufacturers to users of assays for prolactin regarding interference by macroprolactin is absent or inadequate and does not comply with the European Union Regulation covering in vitro diagnostic medical devices (IVDR). As the IVDR is implemented notified bodies should insist that manufacturers of assays for serum prolactin comply with the regulations by informing users that macroprolactin is a source of interference which may have untoward clinical consequences and by providing an estimate of the magnitude of the interference and a means of detecting macroprolactinaemia. Laboratories should institute a policy for excluding macroprolactinaemia in all cases of hyperprolactinaemia.

Hormone Immunoassay Interference: A 2021 Update

Immunoassays are powerful qualitative and quantitative analytical techniques. Since the first description of an immunoassay method in 1959, advances have been made in assay designs and analytical characteristics, opening the door for their widespread implementation in clinical laboratories. Clinical endocrinology is closely linked to laboratory medicine because hormone quantification is important for the diagnosis, treatment, and prognosis of endocrine disorders. Several interferences in immunoassays have been identified through the years; although some are no longer encountered in daily practice, cross-reaction, heterophile antibodies, biotin, and anti-analyte antibodies still cause problems. Newer interferences are also emerging with the development of new therapies. The interfering substance may be exogenous (e.g., a drug or substance absorbed by the patient) or endogenous (e.g., antibodies produced by the patient), and the bias caused by interference can be positive or negative. The consequences of interference can be deleterious when clinicians consider erroneous results to establish a diagnosis, leading to unnecessary explorations or inappropriate treatments. Clinical laboratories and manufacturers continue to investigate methods for the detection, elimination, and prevention of interferences. However, no system is completely devoid of such incidents. In this review, we focus on the analytical interferences encountered in daily practice and possible solutions for their detection or elimination.

Macroprolactin: From laboratory to clinical practice

Prolactin measurement is very common in standard clinical practice. It is indicated not only in the study of pituitary adenomas, but also when there are problems with fertility, decreased libido, or menstrual disorders, among other problems. Inadequate interpretation of prolactin levels without contextualizing the laboratory results with the clinical, pharmacological, and gynecological/urological history of patients leads to erroneous diagnoses and, thus, to poorly based studies and treatments. Macroprolactinemia, defined as hyperprolactinemia due to excess macroprolactin (an isoform of a greater molecular weight than prolactin but with less biological activity), is one of the main causes of such erroneous diagnoses, resulting in poor patient management when not recognized. There is no unanimous agreement as to when macroprolactin screening is required in patients with hyperprolactinemia. At some institutions, macroprolactin testing by polyethylene glycol (PEG) precipitation is routinely performed in all patients with hyperprolactinemia, while others use a clinically based approach. There is also no consensus on how to express the results of prolactin/macroprolactin levels after PEG, which in some cases may lead to an erroneous interpretation of the results. The objectives of this study were: 1. To establish the strategy for macroprolactin screening by serum precipitation with PEG in patients with hyperprolactinemia: universal screening versus a strategy guided by the alert generated by the clinician based on the absence or presence of clinical symptoms or by the laboratory when hyperprolactinemia is detected. 2. To create a consensus document that standardizes the reporting of prolactin results after precipitation with PEG to minimize errors in the interpretation of the results, in line with international standards.

Gender-specific reference intervals for serum prolactin concentrations before and after precipitation by polyethylene glycol

Prolactin, a hormone secreted by the anterior pituitary, exists in three major forms in circulation. The macroprolactin form is biologically inactive but contributes to elevated serum prolactin concentrations. Precipitation of macroprolactin by polyethylene glycol (PEG) is widely used in clinical laboratories for the screening of macroprolactin. The aim of this study was two-fold. Firstly, we sought to establish locally relevant reference intervals for serum prolactin and post-PEG precipitation prolactin concentrations in both genders on the Roche Cobas Prolactin II electrochemiluminescence immunoassay. Secondly, the prolactin concentrations after precipitation by PEG dissolved in phosphate-buffered saline (post-PEG(PBS)) were compared with those after precipitation by PEG dissolved in deionised water (PEG(diH2O)). Prolactin concentrations were measured by using the Prolactin Gen II assay on a Roche Cobas e601 analyser. Recoveries of prolactin after precipitation by PEG in PBS and PEG in diH2O were 64.7%–115.8% and 60.9–100.8%, respectively. Post-PEG (PBS) prolactin concentrations were not statistically different from post-PEG (diH2O) prolactin concentrations in either gender.

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.

The Interdisciplinary Management of Newly Diagnosed Pituitary Tumors

BACKGROUND

The increasing use of cranial tomographic imaging has led to the more frequent discovery of pituitary tumors. In this review, we discuss the clinical symptoms that point toward a pituitary tumor, the required diagnostic studies, the potential need for follow-up studies, and the indications for neurosurgical treatment.

METHODS

This review is based on pertinent publications from the years 2005-2020 that were retrieved by a selective search in PubMed, as well as on the current German S2k guideline, which was created with the present authors playing a coordinating role, and on further guidelines from abroad. Relevant information from older reviews was also considered.

RESULTS

The reported prevalence of pituitary tumors varies depending on the method of data acquisition. Autopsy studies yield a figure of 10.7%, while population-based studies reported 77.6-115.6 cases per 100 000 inhabitants. These lesions are nearly always benign, and 85% of them are pituitary adenomas. Pituitary adenomas measuring less than 1 cm in diameter are called microadenomas, while those measuring 1 cm or more are called macroadenomas. According to magnetic resonance imaging (MRI) studies, the prevalence of microadenomas in the general population is in the range of 10-38%, while that of macroadenomas is 0.16-0.3%. Pituitary adenomas can be either hormonally inactive or hormonally active. Half of all patients with hormonally inactive microadenomas display no endocrine abnormality, while 37-85% of patients with hormonally inactive macroadenomas manifest at least partial pituitary insufficiency. The clinical spectrum of pituitary tumors ranges from a fully asymptomatic state to visual disturbances, neurologic deficits, severe hormone excess (e.g., in Cushing disease), and life-threatening pituitary insufficiency. Pituitary adenomas are often diagnosed only after a latency of many years, even when they are symptomatic. If an imaging study shows the tumor to be in contact with the visual pathway, an ophthalmological evaluation should be performed. There are clear indications for surgery, e.g., imminent loss of vision, but most asymptomatic pituitary tumors can be observed only.

CONCLUSION

The manifestations of pituitary tumors are first recognized by primary care physicians. The further diagnostic evaluation of these patients should be carried out in standardized and interdisciplinary fashion.

Optimization of a Screening Method for Macroprolactinemia

OBJECTIVE

To optimize a screening method for macroprolactinemia and improve the accuracy of free prolactin (freePRL) detection.

METHOD

Overall efficiency, calculated as the product of the immunoglobulin G (IgG) precipitation rate and the freePRL recovery rate were employed to determine the concentration of the precipitant polyethylene glycol (PEG). Then, an optimized screening method for macroprolactinemia was established. The concentrations of freePRL, obtained by gel filtration chromatography (GFC), from 66 cases were used as the gold standard, and the sensitivity, specificity, accuracy and precision of the optimized and traditional methods for detecting macroprolactinemia were compared.

RESULTS

(1) The IgG precipitation rate increased with increasing PEG6000 concentration, and the freePRL recovery rate decreased with increasing PEG6000 concentration; the overall efficiency first increased and then decreased. When the IgG concentrations in the mixture were 10 g/L, 25 g/L and 40 g/L, the concentrations of PEG6000 with the highest overall efficiency were 24%, 20% and 18%, respectively. (2) The effect of high and low IgG on the overall efficiency was 4.7% when using 20% PEG6000, which was lower than the effects when using 18% or 24% PEG6000 (9.2% and 13.2%). (3) In the optimized method established using 20% PEG6000, the macroprolactin (macroPRL) chromatographic peak disappeared, but the freePRL chromatographic peak was retained. The sensitivity of this macroprolactinemia screening method was 96.7%, and the specificity was 100%. (4) The freePRL concentrations obtained by the optimized method for samples from 30 macroprolactinemia cases and 36 true hyperprolactinemia cases were 15.8 (10.2-21.4) ng/mL and 60.2 (51.8-79.9) ng/mL; the concentrations were similar to those obtained using the GFC method (16.3 (11.9-27.2) ng/mL and 68.1 (49.5-92.9) ng/mL, respectively (p > 0.05)) and higher than those obtained using the traditional method (9.1 (6.1-17.6) ng/mL and 51.4 (43.7-71.9) ng/mL), respectively, p < 0.05)). (5) The relative deviation between the optimized and GFC methods was -7.0%, which was significantly lower than the relative deviation between the traditional and GFC methods (-21.4%, p < 0.01). (6) The in-batch coefficients of variation (CVs) for the dual-level quality control materials measured by the optimized method were 1.88% and 1.87%, and the within-laboratory CVs were 2.55% and 2.29%, which were slightly lower than the in-batch CVs (1.93% and 2.81%) and within-laboratory CVs (2.75% and 2.81%) measured by the traditional method.

CONCLUSION

The established optimized method for screening macroprolactinemia using 20% PEG6000 as a precipitant can completely precipitate macroPRL components and effectively retain freePRL components. Compared with traditional methods, the optimized method is simpler, more accurate and more stable for the quantitative detection of freePRL.

Macroprolactin: From laboratory to clinical practice

Prolactin measurement is very common in standard clinical practice. It is indicated not only in the study of pituitary adenomas, but also when there are problems with fertility, decreased libido, or menstrual disorders, among other problems. Inadequate interpretation of prolactin levels without contextualizing the laboratory results with the clinical, pharmacological, and gynecological/urological history of patients leads to erroneous diagnoses and, thus, to poorly based studies and treatments. Macroprolactinemia, defined as hyperprolactinemia due to excess macroprolactin (an isoform of a greater molecular weight than prolactin but with less biological activity), is one of the main causes of such erroneous diagnoses, resulting in poor patient management when not recognized. There is no unanimous agreement as to when macroprolactin screening is required in patients with hyperprolactinemia. At some institutions, macroprolactin testing by polyethylene glycol (PEG) precipitation is routinely performed in all patients with hyperprolactinemia, while others use a clinically based approach. There is also no consensus on how to express the results of prolactin/macroprolactin levels after PEG, which in some cases may lead to an erroneous interpretation of the results. The objectives of this study were: 1. To establish the strategy for macroprolactin screening by serum precipitation with PEG in patients with hyperprolactinemia: universal screening versus a strategy guided by the alert generated by the clinician based on the absence or presence of clinical symptoms or by the laboratory when hyperprolactinemia is detected. 2. To create a consensus document that standardizes the reporting of prolactin results after precipitation with PEG to minimize errors in the interpretation of the results, in line with international standards.

Macro-TSH: A Diagnostic Challenge

INTRODUCTION

Analytical problems should be considered in case of a discrepancy between the results of biochemical tests and the clinical findings. Macro-hormones often artefactually elevate biochemical tests.

CASE PRESENTATION

A young male was referred with persistently elevated TSH (148 mIU/L) measured by a sandwich electrochemiluminescence immunoassay, ECLIA (Cobas; Roche, Basel, Switzerland). The patient's complaints were unspecific, and he appeared clinically euthyroid. The plasma levels of free T4 and free T3 were within the normal range, thyroid autoantibodies were negative, and thyroid ultrasonography was normal. During a short trial of thyroid hormone substitution, the level of TSH decreased to near-normal levels, but hyperthyroid symptoms emerged. TSH analysed by a different immunoassay (Architect; Abbott, Chicago, IL, USA) yielded similar results. In addition, serial dilutions were performed showing linearity, without detection of heterophilic antibody interference. Gel filtration chromatography confirmed the presence of macro-TSH.

CONCLUSION

The patient harboured macro-TSH, which is a rare condition. The complex binding of TSH to other plasma proteins, most often immunoglobulins, results in elevated plasma TSH. However, the biologically active fraction of TSH is normal, reflected by clinical and biochemical euthyroidism.

Antipsychotics-induced hyperprolactinemia and screening for macroprolactin

Introduction

High prolactin (PRL) concentrations are found in laboratory test results of patients on majority of antipsychotic drugs. Prevalence rates and degrees of severity of hyperprolactinemia (HPRL) based on PRL concentration may depend on the presence of macroprolactin in the serum. The aim of the study was to investigate the difference between PRL concentrations before and after precipitation of macroprolactin and to examine if there were any changes in the categorization of HPRL between samples prior and after precipitation.

Materials and methods

Total of 98 female patients (median age 33; range 19-47 years) diagnosed with a psychotic disorder, proscribed antipsychotic drugs, and with HPRL were included. Total PRL concentration and PRL concentration after macroprolactin precipitation with polyethylene glycol (postPEG-PRL) were determined by the chemiluminometric method on the Beckman Coulter Access2 analyser.

Results

Total PRL concentrations (median 1471; IQC: 1064-2016 mlU/L) and postPEG-PRL concentrations (median 1453; IQC: 979-1955 mlU/L) were significantly correlated using intraclass correlation coefficient for single measurements (mean estimation 0.96; 95%CI 0.93-0.97) and average measurement (mean estimation 0.98; 95%CI 0.96-0.99), and all investigated female patient had HPRL according to PRL and postPEG-PRL concentration. The median PRL recovery following PEG precipitation was 95; IQC: 90-100%. There was substantial agreement (kappa test = 0.859, 95% CI: 0.764-0.953) between the categories of HPRL severity based on total PRL concentrations and postPEG-PRL concentrations.

Conclusion

The study demonstrated that HPRL was present in all subjects using the reference interval for total PRL concentration and postPEG-PRL concentration with no significant impact of macroprolactin presence in the serum on the categorization of patients according to severity of HPRL.

Biochemical diagnosis in prolactinomas: some caveats

Prolactinomas are the most frequently seen pituitary adenomas in clinical practice. A correct biochemical diagnosis of hyperprolactinemia is a prerequisite for further investigation but may be hampered by analytical difficulties as well as a large number of potentially overlapping conditions associated with increased prolactin levels. Suspicion should rise in patients whose symptoms and biochemical results do not match. Assay problems, macroprolactinemia, and high-dose hook effect are discussed as possible reasons for false positive or false negative prolactin levels. Physiological and pathological causes of hyperprolactinemia and their implications for interpreting prolactin results are reviewed.

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.