Fahie-Wilson M N, John R, Ellis A R
Department of Clinical Biochemistry, Southend Hospital, Westcliff-on-Sea, Essex SS0 0RY, UK.
Ann Clin Biochem. 2005 May;42(Pt 3):175-92. doi: 10.1258/0004563053857969.
Two high molecular mass forms of prolactin (PRL) in serum have been identified by gel filtration chromatography (GFC): macroprolactin (big-big PRL, > 100 kDa) and big PRL (40-60 kDa). Macroprolactin has a variable composition and structure, but is most frequently a complex of PRL and IgG, with a molecular mass of 150-170 kDa. It is formed in the circulation following pituitary secretion of monomeric PRL but has a longer half-life, and the PRL in the complex remains reactive to a variable extent in immunoassays. In the majority of subjects little or no macroprolactin can be detected in serum, but in some individuals it may be the predominant immunoreactive component of circulating PRL and the cause of apparent hyperprolactinaemia. Owing to its high molecular mass, macroprolactin appears to be confined to the intravascular compartment and much evidence indicates that it has minimal bioactivity in vivo and is not of pathological significance. Nevertheless, hyperprolactinaemia due to macroprolactin can lead to diagnostic confusion and unnecessary further investigation and treatment if it is not recognized as such. Macroprolactin is a common cause of apparent hyperprolactinaemia with some assays and it is essential that laboratories introduce screening programmes to examine samples with elevated total immunoreactive PRL for the presence of macroprolactin and determine the monomeric PRL component which is known to be bioactive in vivo. A number of screening tests have been described; that based on the precipitation of macroprolactin with polyethylene glycol has been the most widely validated and applied. The reference technique of GFC should be available for confirmation and further investigation of samples, giving equivocal results in screening tests. In comparison with macroprolactin, little is known about big PRL. It is a more consistent component of total serum PRL but rarely, if ever, the cause of hyperprolactinaemia. Further research is required into the nature of macroprolactin and big PRL, the relationships between high molecular mass forms of PRL, and their clinical significance.
通过凝胶过滤色谱法（GFC）已在血清中鉴定出两种高分子量形式的催乳素（PRL）：大催乳素（大大PRL，>100 kDa）和大PRL（40 - 60 kDa）。大催乳素具有可变的组成和结构，但最常见的是PRL与IgG的复合物，分子量为150 - 170 kDa。它在垂体分泌单体PRL后在循环中形成，但半衰期更长，并且复合物中的PRL在免疫测定中仍有不同程度的反应性。在大多数受试者的血清中几乎检测不到或根本检测不到大催乳素，但在一些个体中，它可能是循环PRL的主要免疫反应成分以及明显高催乳素血症的原因。由于其高分子量，大催乳素似乎局限于血管内隔室，并且大量证据表明它在体内具有最小的生物活性且无病理意义。然而，如果不被识别出来，由大催乳素引起的高催乳素血症会导致诊断混淆以及不必要的进一步检查和治疗。大催乳素是某些检测中明显高催乳素血症的常见原因，实验室必须引入筛查程序，以检查总免疫反应性PRL升高的样本中是否存在大催乳素，并确定已知在体内具有生物活性的单体PRL成分。已经描述了许多筛查试验；基于用聚乙二醇沉淀大催乳素的试验是最广泛验证和应用的。GFC的参考技术应可用于对筛查试验结果不明确的样本进行确认和进一步研究。与大催乳素相比，人们对大PRL了解甚少。它是总血清PRL中更一致的成分，但很少（如果有的话）是高催乳素血症的原因。需要进一步研究大催乳素和大PRL的性质、PRL高分子量形式之间的关系及其临床意义。
