title: Quantitative adjustment for macroprolactin is an integral part of laboratory assessment of hyperprolactinaemia.
abstract: BACKGROUND
  Prolactin circulates predominantly as a 23-kDa monomer, and a high-molecular-weight form largely consisting of a complex of prolactin and an anti-prolactin IgG autoantibody, called macroprolactin. This cross-reacts with conventional laboratory assays for prolactin. We here describe how quantitative adjustment for this may assist patient management.In a consecutive series of 218 patients with prolactin elevated to 400 mu/L or more in men (normal range ≤ 180) (n=79, 36.2% of sample) and 1 000 mu/L or more in women (normal range ≤ 500) (n=139, 63.8%) a macroprolactin screen was performed using PEG precipitation.
  
  
  RESULTS
  Where present, median macroprolactin as a proportion of total prolactin was in women 13% (percentile 25-percentile 75: 7-25%) and in men 15% (7-30%).The distribution of macroprolactin as a proportion of total prolactin was markedly skewed to the left with 69.7% of women and 62.9% of men having macroprolactin proportion of 20% or less. There was no relation between %macroprolactin and total measured prolactin, age or gender.Of relevance to clinical management, in 24% of men and 20.5% of women, correction for estimated macroprolactin gave an adjusted monomeric prolactin level below the agreed threshold for further investigation, potentially avoiding unnecessarily referral.In our clinical series, quotation of an adjusted monomeric prolactin would have resulted in unnecessary further investigation being avoided in a number of cases.
  
  
  CONCLUSIONS
  Screening for macroprolactin is a key element of laboratory assessment for hyperprolactinaemia.In cases where measured total prolactin is significantly raised, quantitative reporting of estimated monomeric prolactin instead of just 'macroprolactin' positive' can avoid unnecessary investigations.
authors.affiliation: Department of Endocrinology, Leighton Hospital, Crewe, CW1 4QJ, UK. adrian.heald@manchester.ac.uk
authors.forename: A H
authors.initials: AH
authors.lastname: Heald
authors.forename: E
authors.initials: E
authors.lastname: Blantern
authors.forename: S G
authors.initials: SG
authors.lastname: Anderson
authors.forename: D
authors.initials: D
authors.lastname: Radford
authors.forename: Z
authors.initials: Z
authors.lastname: Qureshi
authors.forename: S
authors.initials: S
authors.lastname: Nair
authors.forename: J
authors.initials: J
authors.lastname: Waldron
authors.forename: M
authors.initials: M
authors.lastname: Davies
authors.forename: A
authors.initials: A
authors.lastname: McCulloch
authors.forename: J
authors.initials: J
authors.lastname: Kane
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002138:Calibration; D019411:Clinical Laboratory Techniques / Q000379:methods* / Q000592:standards; D003940:Diagnostic Techniques, Endocrine / Q000592:standards; D005260:Female; D006801:Humans; D006966:Hyperprolactinemia / Q000097:blood / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011388:Prolactin / Q000032:analysis / Q000097:blood*; D012016:Reference Values; D012189:Retrospective Studies; D012727:Sex Characteristics; D055815:Young Adult
chemical_list: C060678:prolactin, polymeric; D011388:Prolactin