IgA-type macroprolactin among 130 patients with macroprolactinemia

Masayuki Ishihara; Naoki Hattori; Norito Nishiyama; Kozo Aisaka; Takashi Adachi; Takanori Saito

doi:10.1515/cclm-2025-0264

Article

IgA-type macroprolactin among 130 patients with macroprolactinemia

Masayuki Ishihara , Naoki Hattori , Norito Nishiyama , Kozo Aisaka , Takashi Adachi and Takanori Saito

Published/Copyright: April 8, 2025

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From the journal Clinical Chemistry and Laboratory Medicine (CCLM) Volume 63 Issue 9

Abstract

Objectives

Macroprolactin (macro-PRL) mostly comprises a complex of PRL with IgG. The aim of this study was to clarify whether IgA-type macro-PRL exists and, if so, to elucidate the prevalence of and differences in laboratory data from IgG-type.

Methods

One hundred thirty patients with macroprolactinemia who were diagnosed through screening via the polyethylene glycol precipitation method followed by confirmation using gel filtration chromatography (GFC) were examined. IgA-type and IgG-type macro-PRLs were identified via Jacalin column/SDS‒PAGE and protein G columns, respectively.

Results

SDS‒PAGE under nonreducing conditions followed by western blotting with an IgA antibody revealed that the fraction bound to the Jacalin column was actually IgA. The PRL band was detected at the same position as the IgA band, which was purified with a Jacalin column, suggesting that PRL was bound to IgA. The finding that the PRL band was observed not only at the same position as IgA but also at the same position as the 23 kDa PRL reference suggested that some PRL dissociated from IgA during SDS‒PAGE. The prevalence rates of macro-PRL of only IgA, IgA plus IgG, only IgG, and non-IgA/non-IgG types were 7.7, 3.1, 83.8, and 5.4 %, respectively. Neither the PEG precipitation ratios of PRL nor the macro-PRL ratios on GFC differed between IgA- and IgG-type macro-PRLs, whereas both ratios were significantly lower in non-IgA/non-IgG-type macro-PRL.

Conclusions

IgA-type macro-PRL was demonstrated to exist. IgG-type macro-PRL was most prevalent, followed by IgA, non-IgA/non-IgG and IgA plus IgG-type macro-PRLs.

Keywords: IgA; IgG; macroprolactin; macroprolactinemia; hyperprolactinemia

Corresponding author: Naoki Hattori, MD, PhD, Department of Orthopedic Surgery, Kansai Medical University, 2-5-1 Shinmachi, Hirakata, Osaka, 573-1010, Japan, E-mail: hattorin@hirakata.kmu.ac.jp

Research ethics: This study was approved by the Clinical Research Review Board of the Hamada Obstetrics and Gynecology Hospital and the Research Ethics Review Board of the Kansai Medical University. This research was completed in accordance with the Declaration of Helsinki.
Informed consent: Informed consent was obtained from the participants included in this study.
Author contributions: Masayuki Ishihara and Naoki Hattori conceived and performed the experiments, and wrote the manuscript in consultation with Takanori Saito. Kohozo Aisaka contributed to clinical sample collection and the analysis of the clinical data. Norito Nishiyama and Takashi Adachi carried out the experiments. All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
Use of Large Language Models, AI and Machine Learning Tools: None declared.
Conflict of interest: The authors state no conflict of interest.
Research funding: None declared.
Data availability: The raw data can be obtained on request from the corresponding author.

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Received: 2025-03-06

Accepted: 2025-03-29

Published Online: 2025-04-08

Published in Print: 2025-08-26

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Articles in the same Issue

https://doi.org/10.1515/cclm-2025-0264

Keywords for this article

IgA; IgG; macroprolactin; macroprolactinemia; hyperprolactinemia