Endocrine Abstracts

Background: A number of studies have evaluated the association between prolactin (PRL) and breast cancer risk, but some results have been inconsistent.

The aim of this study was to investigate, if the circadian rhythm of PRL was maintained in pre- and post-menopausal patients with breast cancer and if there is a correlation between serum PRL level, serum concentration of insulin-like growth factor 1 (IGF1), tumor staging and expression of estrogen, progesterone and HER2 receptors in tumor tissue.

Patients and methods: Sixty-four women with the breast cancer aged 36–78 years and 20 healthy controls matched for age were studied. Serum PRL was determined using immunoradiometric method. Blood samples for PRL determination were taken four times daily at fixed hours of the 24 h cycle and obtained results were analysed using the Cosinor test.

Results: Sixteen patients with breast cancer (25%) demonstrated high serum PRL level, and 29 (45%) showed high serum IGF1 level. Circadian rhythm of PRL was maintained in all patients with breast cancer. Both in patients and in healthy subjects the circadian rhythm indicated the highest serum concentration of PRL in night hours.

Both in pre-menopausal as well as in post-menopausal patients there was no statistically significant correlation between serum PRL, IGF1 levels, the degree of tumor staging and expression of estrogen, progesterone and HER2 receptors in the tumor.

Conclusions: Patients with breast cancer show a circadian rhythm of prolactin release, not significantly different from rhythm in healthy subjects.

Some patients with breast cancer demonstrated hyperprolactinaemia and/or high serum IGF1 level. These data suggest that higher plasma PRL and IGF1 levels could be associated with an increased risk of breast cancer.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.