Local thyroid renin-angiotensin system in experimental breast cancer

An association between breast cancer and thyroid dysfunction exists although the underlying mechanisms remain to be elucidated. Numerous studies have characterized the role of thyroid hormones in controlling the synthesis and secretion of renin-angiotensin system (RAS) components, but little information is available on the putative role of the local RAS on thyroid function.AimsHere we analyze several soluble and membrane-bound RAS-regulating aminopeptidase activities in thyroid gland from rats with mammary tumors and the relationship with the circulating levels of thyroid stimulating hormone (TSH) and free thyroxin (fT4).Main methodsWe analyze soluble and membrane-bound RAS-regulating aminopeptidase activities fluorometrically using their corresponding aminoacyl-β-naphthylamide as the substrate.Key findingsWe have found in rats with mammary tumors a concomitant change of thyroid RAS-regulating enzymes and thyroid hormone production.SignificanceWe suggest that existence of alterations in the regulatory mechanisms mediated by the angiotensins of the local tissue RAS as a consequence of the carcinogenic process which could act alone or in combination with alterations at a higher level of regulation such as the hypothalamus-pituitary axis.