Prolactin stimulation of parathyroid adenomas

Primary hyperparathyroidism is a common endocrine disorder frequently affecting postmenopausal women. In this study we have investigated expression of the prolactin receptor (PRLr) in a panel of 37 sporadic parathyroid tumours, as well as functionality in vitro in cultured parathyroid tumour cells. High levels of the prolactin receptor gene (PRLR) transcripts were demonstrated in parathyroid tissues as compared to other reference tissues and breast cancer cells. PRLr products of 60/70 kDa were highly expressed in all parathyroid tumours. In addition varying levels of the 80 kDa PRLr isoform, with known proliferative activity, were demonstrated. In parathyroid tumours PRLr immunoreactivity was observed in cytoplasm in all cases and in addition in the plasma membrane (n = 12) or enlarged lysosomes (n = 4). In normal parathyroid rim PRLr was expressed in cytoplasm and granulae. In in vitro studies of short-term cultured human parathyroid tumour cells prolactin stimulation was associated with transcriptional changes in JAK/STAT, RIG-I like receptor and type II interferon signaling pathways as documented by gene expression profiling. Moreover, PRLR gene expression in parathyroid tumors was significantly inversely correlated with plasma total Ca2+ levels. In conclusion, the prolactin receptor was found highly abundant in human parathyroid gland, parathyroid tumours, correlated with patient Ca2+ levels and functionally responsive to physiological levels of prolactin. These findings suggest a role for the prolactin receptor in human parathyroid adenomas.

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Haglund F, Lu M, Vukojević V, Nilsson IL, Andreasson A, Džabić M, Bränström R, Höög A, Juhlin CC, Larsson C