SFEBES2008 Poster Presentations Pituitary (62 abstracts)
Adjustment for macroprolactin: an integral part of laboratory assessment of hyperprolactinaemia
Liz Blantern 1 , Zubair Qureshi 1 , Adrian Heald 1 , Simon Anderson 2 , Daniela Radford 1 , Julian Waldron 1 , Marten Davies 3 , Alan McCulloch 3 & John Kane 4
1Leighton Hospital, Crewe, Cheshire, UK; 2Bishop Auckland General Hospital, Bishop Auckland, Co Durham, UK; 3Department of Cardiovascular and Endocrine Sciences, University of Manchester, Manchester, UK; 4Salford Royal Hospitals Foundation Trust, Salford, UK.
Background: In most people, prolactin circulates predominantly as a 23-kDa monomer, and a high-molecular-weight form which in the vast majority of cases consists of a complex of prolactin and an anti-prolactin IgG autoantibody, commonly referred to as macroprolactin. This cross-reacts with conventional laboratory assays for prolactin.
Report: In a consecutive series of 218 patients with prolactin elevated to 400 μ/l or more in men (normal range ≤180) (n=79, 36.2% of sample) and 1000 μ/l or more in women (normal range ≤500) (n=139, 63.8%) a macroprolactin screen was performed using PEG precipitation. Our aim was to determine the distribution of macroprolactin and the relevance of its measurement. Source of referral was primary care and secondary care services.
About 68.3% of men and 71.2% of women had detectable macroprolactin. 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 or age, and no difference by gender.
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 (400 μ/l in men and 1000 μ/l in women), thus avoiding unnecessarily referral.
Discussion: Screening for macroprolactin is a key element of laboratory assessment for hyperprolactinaemia. Macroprolactin proportion was not influenced by total prolactin, gender or age.
In cases where measured prolactin is significantly raised, reporting of estimated monomeric prolactin instead of just ‘macroprolactin positive’ may avoid unnecessary investigations.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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