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Objective: To review the current literature regarding the prevalence of macroprolactin (macroPRL) in hyperprolactinemic patients and determine recommendations for testing., Methods: An electronic United States National Library of Medicine PubMed search (through October, 2014) was conducted for search term "macroprolactin." Only English-language articles were considered., Results: MacroPRL is an under-recognized cause of elevated prolactin (PRL) and is present in approximately 4% to 40% of hyperprolactinemic patients depending on the referral population. Clinical findings which could be due to hyperprolactinemia are the impetus for testing for PRL. Because of this there is significant overlap in the clinical presentation of patients with true hyperprolactinemia and those with macroPRL, differentiation cannot always be made on the basis of symptoms. A lack of recognition of the presence of macroPRL can lead to unnecessary laboratory investigations, imaging, and pharmacologic or surgical treatment., Conclusion: Until there is a commercially available PRL assay that is not subject to interference by macroPRL, clinicians should consider the possibility of macroPRL, especially if the clinical presentation, imaging findings, and/or response to therapy reveal inconsistencies.

A number of important factors determine the risk for breast cancer, and the most important of these seem to be related to estrogen and possibly prolactin. Additional research is necessary on the role of endogenous and exogenous estrogens and the effect of diet, drugs, and other factors on the levels of estrogen and prolactin. It is unlikely that with present epidemiologic evidence, breast cancer can be prevented. We cannot alter the age of menarche, and promotion of early pregnancy to protect against breast cancer is not feasible. One risk factor that is alterable is obesity, particularly in the postmenopausal woman. The risk factors associated with exogenous estrogens following the menopause require confirmation by other studies. However, because of the strong association of these drugs with increased risk of endometrial cancer, the physician should be cautious in prescribing them.

Various factors have been found to be predictors of the relative risk of breast cancer (Table 2). Epidemiologic variables influencing breast cancer risk include age, marital status, geographic location, racial or ethnic extraction, and socioeconomic status. The risk of developing mammary carcinoma is increased with advancing age, among unmarried women, in the United States and Europe, and among women of higher socioeconomic classes. Conversely, a decreased breast cancer risk is observed among fertile married women in Asian countries, among Oriental women, and in lower socioeconomic classes. Reproductive history plays an important role in determining breast cancer risk. The risk of developing mammary carcinoma is increased by an early menarche and decreased by delayed first menses. A late natural menopause increases breast cancer risk while an early oophorectomy offers protection. Hormonal factors are thought to play important roles in the etiology of breast cancer, but the contributions of estrogenic and androgenic influences to mammary neoplasia have not been delineated. Certain estrogen fractions have been implicated as mammary carcinogens, while certain adrenal androgenic steroids have been shown to be promotors of breast cancers. Chronic cystic mastitis is associated with an increased breast cancer risk. A positive family history increases the risk of developing mammary carcinoma and a past history of breast cancer markedly increases the possibility of subsequent breast neoplasia.