Article Reply to the Letter of Sun et al. [1] relating to Clin Chem Lab Med 2022;60(9):1365–72 was published on October 1, 2022 in the journal Clinical Chemistry and Laboratory Medicine (CCLM) (volume 60, issue 11).

Abstract 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.

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 subfractionated 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. (C) 2013 Elsevier Ltd. All rights reserved.

Lassen Peak is one of two Cascade volcanoes to erupt during the twentieth century. Eruptions from 1914 to 1917 produced numerous small phreatic explosions, a pyroclastic flow, and viscous dacite lava near the summit, which mixed with snow and triggered lahars. Earlier episodes of volcanism include the development of silicic domes at Chaos Crags (1,100 to 1,000 yr ago) followed by dome collapse (Chaos Jumbles). Fumarolic activity at several sites continues near Lassen Peak.

Prolactin is the hormone most commonly measured in patients evaluated for reproductive disorders. The biologically active form of prolactin is the 23-kDa monomeric polypeptide secreted by the pituitary gland; however, circulating prolactin exists in a number of additional forms. Big prolactin (60 kDa) and macroprolactin (150 kDa), which are present in serum in varying quantities, can cause apparent hyperprolactinemia, but they have no clinical importance because they exhibit little biological activity. Despite efforts to improve assay specificity, all prolactin immunoassays in routine use detect both big prolactin and macroprolactin to varying degrees (1). The polyethylene glycol (PEG) precipitation test is widely used to detect pseudohyperprolactinemia caused by big prolactin and/or macroprolactin. Current best practice recommends that all sera with increased total prolactin concentrations be subfractionated by PEG precipitation to measure the bioactive monomeric prolactin concentration, a more clinically meaningful variable (2)(3). Subfractionation with PEG allows laboratories to distinguish patients with true hyperprolactinemia, in which there are supraphysiological concentrations of bioactive monomeric prolactin, from those with macroprolactinemia, which is characterized by increased concentrations of macroprolactin and/or big prolactin together with normal concentrations of bioactive monomeric prolactin. In the absence of PEG screening, misdiagnosis and consequent …

CONTEXT:The insulin tolerance test (ITT) is the gold standard for assessment of ACTH and GH reserve in patients with suspected hypopituitarism. It is labor intensive and costly.OBJECTIVE:The objective of the study was to determine whether use of the overnight metyrapone test (OMT) and plasma IGF-I sd scores (SDS) could provide a cost-effective alternative to the ITT.DESIGN:This was a retrospective chart review.SETTING:The study was conducted at a teaching hospital.PARTICIPANTS AND INTERVENTION:Charts from 100 patients with organic pituitary disorders were reviewed. All underwent the OMT unless 0900 h plasma cortisol was less than 80 or greater than 450 nmol/liter when ACTH deficiency or ACTH sufficiency, respectively, was diagnosed. Patients were considered GH deficient if the age-related IGF-I SDS was less than -3 or if they had three or more other pituitary hormone deficiencies. Patients were considered GH sufficient if age-related IGF-I SDS was greater than the 95th centile established from patients with known GH deficiency. Thirty-three underwent an ITT.MAIN OUTCOME MEASURES:The proportion of patients in whom ACTH and GH reserve could be assessed using OMT/IGF-I SDS was measured. The concordance with results was obtained from ITT.RESULTS:Fifty-five patients were ACTH sufficient and 45 were ACTH deficient. Twenty-one were GH sufficient and 33 were GH deficient based on IGF-I SDS and other pituitary hormone deficiencies, whereas 46 could not be classified. There was near-uniform concordance between OMT/IGF-I SDS and ITT. Initial investigation using OMT/IGF-I SDS resulted in a significant cost saving.CONCLUSIONS:ACTH and GH reserve can be accurately and cost-effectively investigated using OMT/IGF-I SDS in approximately 50% of patients with organic pituitary disorders.

Abstract: Macroprolactin is a frequently unrecognized phenomenon giving rise to inaccurate diagnosis in an estimated 10% of cases of hyperprolactinemia in the United States. This has been associated with unnecessary investigation and inappropriate treatment including pituitary exploration. Simple laboratory procedures can be adapted to routinely screen hyperprolactinemic sera for macroprolactin. Therefore, it is timely to alert endocrinologists, gynecologists, and all those involved in the management of hyperprolactinemia to macroprolactin, its frequent occurrence and its ready recognition. Demand by clinicians to establish routine screening of hyperprolactinemic sera for the presence of macroprolactin will be useful in leading to adoption of routine screening procedures necessary for the appropriate recognition of the phenomenon.

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

BACKGROUND:Macroprolactin is an important source of immunoassay interference that commonly leads to misdiagnosis and mismanagement of hyperprolactinemic patients. We used the predominant immunoassay platforms for prolactin to assay serum samples treated with polyethylene glycol (PEG) and establish and validate reference intervals for total and monomeric prolactin.METHODS:We used the Architect (Abbott), ADVIA Centaur and Immulite (Siemens Diagnostics), Access (Beckman Coulter), Elecsys (Roche Diagnostics), and AIA (Tosoh) analyzers with samples from healthy males (n = 53) and females (n = 93) to derive parametric reference intervals for total and post-PEG monomeric prolactin. Concentrations of immunoreactive prolactin isoforms in serum samples from healthy individuals were established by gel filtration chromatography (GFC). We then used samples from 22 individuals whose hyperprolactinemia was entirely attributable to macroprolactin and 32 patients with true hyperprolactinemia to compare patient classifications and prolactin concentrations measured by GFC with the newly derived post-PEG reference intervals.RESULTS:Parametric reference intervals for post-PEG prolactin in male and female serum samples, respectively, were (in mIU/L): 61-196, 66-278 (Centaur); 63-245, 75-381 (Elecsys); 70-301, 92-469 (Access); 72-229, 79-347 (Architect); 73-247, 83-383 (AIA); and 78-263, 85-394 (Immulite). Concordance between GFC and immunoassay-specific post-PEG reference intervals was observed in 311 of 324 cases and for 31 of 32 patients with true hyperprolactinemia and 17 of 22 patients with macroprolactinemia. Results leading to misclassification occurred in a few analyzers for 5 macroprolactinemia patient samples with relatively minor increases in post-PEG prolactin (mean 61 mIU/L).CONCLUSIONS:Our validated normative reference data for sera pretreated with PEG and analyzed on the most commonly used immunoassay platforms should facilitate the more widespread introduction of macroprolactin screening by clinical laboratories.

Clinical EndocrinologyVolume 67, Issue 4 p. 639-641 Cushing's syndrome due to a pituitary corticotropinoma in a child with tuberous sclerosis: an association or a coincidence? Radha Nandagopal, Radha Nandagopal Heritable Disorders Branch and Pediatric Endocrinology Inter-Institute Training Program, Developmental Endocrinology Branch (DEB), National Institute of Child Health and Human Development (NICHD),Search for more papers by this authorAlexander Vortmeyer, Alexander Vortmeyer Surgical Neurology Branch, National Institute of Neurological Diseases and Stroke (NINDS) andSearch for more papers by this authorEdward H. Oldfield, Edward H. Oldfield Surgical Neurology Branch, National Institute of Neurological Diseases and Stroke (NINDS) andSearch for more papers by this authorMargaret F. Keil, Margaret F. Keil Pediatric Endocrinology Inter-Institute Training Program, Developmental Endocrinology Branch (DEB), National Institute of Child Health and Human Development (NICHD),Search for more papers by this authorConstantine A. Stratakis, Constantine A. Stratakis Heritable Disorders Branch and Pediatric Endocrinology Inter-Institute Training Program, Developmental Endocrinology Branch (DEB), National Institute of Child Health and Human Development (NICHD), Section on Endocrinology & Genetics, DEB, NICHD, National Institutes of Health, Bethesda, MD 20892, USA. Correspondence: Constantine A. Stratakis, MD, Section on Endocrinology & Genetics (SEGEN), Pediatric Endocrinology Training Program, DEB, NICHD, NIH, Building 10, CRC, Room 1-3330, 10 Center Dr, MSC1103, Bethesda, MD 20892, USA. stratakc@mail.nih.govSearch for more papers by this author Radha Nandagopal, Radha Nandagopal Heritable Disorders Branch and Pediatric Endocrinology Inter-Institute Training Program, Developmental Endocrinology Branch (DEB), National Institute of Child Health and Human Development (NICHD),Search for more papers by this authorAlexander Vortmeyer, Alexander Vortmeyer Surgical Neurology Branch, National Institute of Neurological Diseases and Stroke (NINDS) andSearch for more papers by this authorEdward H. Oldfield, Edward H. Oldfield Surgical Neurology Branch, National Institute of Neurological Diseases and Stroke (NINDS) andSearch for more papers by this authorMargaret F. Keil, Margaret F. Keil Pediatric Endocrinology Inter-Institute Training Program, Developmental Endocrinology Branch (DEB), National Institute of Child Health and Human Development (NICHD),Search for more papers by this authorConstantine A. Stratakis, Constantine A. Stratakis Heritable Disorders Branch and Pediatric Endocrinology Inter-Institute Training Program, Developmental Endocrinology Branch (DEB), National Institute of Child Health and Human Development (NICHD), Section on Endocrinology & Genetics, DEB, NICHD, National Institutes of Health, Bethesda, MD 20892, USA. Correspondence: Constantine A. Stratakis, MD, Section on Endocrinology & Genetics (SEGEN), Pediatric Endocrinology Training Program, DEB, NICHD, NIH, Building 10, CRC, Room 1-3330, 10 Center Dr, MSC1103, Bethesda, MD 20892, USA. stratakc@mail.nih.govSearch for more papers by this author First published: 07 June 2007 https://doi.org/10.1111/j.1365-2265.2007.02941.xCitations: 9 doi: 10.1111/j.1365-2265.2007.02941.x Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume67, Issue4October 2007Pages 639-641 RelatedInformation

Measurement of prolactin is one of the most commonly undertaken hormonal investigations in evaluating patients with reproductive disorders. Hyperprolactinemia is found in up to 17% of such cases. Diagnostic evaluation of hyperprolactinemia is difficult but is facilitated by a logical approach where a thorough patient history is obtained, secondary causes of hyperprolactinemia are excluded, and the limitations of current prolactin assays are appreciated. Once hyperprolactinemia has been confirmed, attempts to establish the underlying cause can start. Given current workloads, laboratories rely on automated platforms to measure prolactin, most of which employ two-site immunoassay sandwich methods. Although generally robust and reliable, such immunoassays are susceptible to interference, and good collaboration between clinicians and the laboratory helps to minimize problems. A major challenge facing laboratories is correct differentiation of patients with true hyperprolactinemia from those with macroprolactinemia. Macroprolactin is a high-molecular-mass, biologically inactive form of prolactin that is detected to varying degrees by all prolactin immunoassays. Conservative estimates suggest that the presence of macroprolactin leads to misdiagnosis in as many as 10% of all reported instances of biochemical hyperprolactinemia. In the absence of specific testing, macroprolactin represents a diagnostic pitfall that results in the misdiagnosis and mismanagement of large numbers of patients.

Clinical EndocrinologyVolume 67, Issue 4 p. 638-639 Macroprolactin and the Pituitary Society guidelines for the diagnosis and management of prolactinomas Michael N. Fahie-Wilson, Michael N. Fahie-Wilson Department of Clinical Chemistry, Southend Hospital, Westcliff-on-Sea, Essex, SSO ORY, UK, andSearch for more papers by this authorTerence Joseph McKenna, Terence Joseph McKenna Department of Endocrinology, St. Vincent's University Hospital, Elm Park, Dublin 4, Ireland.Search for more papers by this authorJames A. Ahlquist, James A. Ahlquist Department of Clinical Chemistry, Southend Hospital, Westcliff-on-Sea, Essex, SSO ORY, UK, andSearch for more papers by this authorThomas P. Smith, Thomas P. Smith Department of Endocrinology, St. Vincent's University Hospital, Elm Park, Dublin 4, Ireland.Search for more papers by this author Michael N. Fahie-Wilson, Michael N. Fahie-Wilson Department of Clinical Chemistry, Southend Hospital, Westcliff-on-Sea, Essex, SSO ORY, UK, andSearch for more papers by this authorTerence Joseph McKenna, Terence Joseph McKenna Department of Endocrinology, St. Vincent's University Hospital, Elm Park, Dublin 4, Ireland.Search for more papers by this authorJames A. Ahlquist, James A. Ahlquist Department of Clinical Chemistry, Southend Hospital, Westcliff-on-Sea, Essex, SSO ORY, UK, andSearch for more papers by this authorThomas P. Smith, Thomas P. Smith Department of Endocrinology, St. Vincent's University Hospital, Elm Park, Dublin 4, Ireland.Search for more papers by this author First published: 30 May 2007 https://doi.org/10.1111/j.1365-2265.2007.02940.xCitations: 3 Michael N. Fahie-Wilson, Fax: 01702 221059; E-mail: mike@leigh.ndo.co.uk doi: 10.1111/j.1365-2265.2007.02940.x Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume67, Issue4October 2007Pages 638-639 RelatedInformation

The anterior pituitary hormone PRL was identified in animal species as early as 1933 1 but only purified in humans in 1972. 2 Since then, the clinical syndrome of hyperprolactinaemia has been characterized extensively, the predominant symptoms being galactorrhoea, oligomenorrhoea or amenorrhoea and infertility in women and reduced libido, impotence and galactorrhoea in men. 3–8 Hyperprolactinaemia has an estimated prevalence of 15% in women with secondary amenorrhoea, 9,10 a condition that affects at least 3% of women of reproductive age. 11

Mate choice tests provided no evidence of prezygotic reproductive isolation between 21 population of Physa virgata (Gould, 1855) collected front its type locality in the Gila River of Arizona and Physa acuta (Draparnaud, 1805) from a control site in Charleston, South Carolina. Reared in,I no-choice experimental design, 10 outcross Arizona X South Carolina pairs initiated reproduction at approximately the same age as Arizona X Arizona controls, and earlier than South Carolina X South Carolina controls. Parents in the outcross experiment did not differ significantly front either control in their median weekly fecundity across 10 weeks of observation, yielding an F, generation with significantly imroved viability. We detected no evidence of reduction in F, fertility Thus, P. virgata, the most widespread freshwater gastropod of the American Southwest,, should be considered a junior Synonym of the cosmopolitan P. acuta.

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.