Circulating levels of cardiac natriuretic hormones measured in women during menstrual cycle

Alterations in fluid and electrolyte balance represent a common complaint b y women during different stages of the menstrual cycle; however, conflictin g results concerning the possible role of plasma Atrial Natriuretic Peptide (ANP) modifications during the menstrual cycle have been reported. This ma y be due to differences in assay methods or in the clinical protocol adopte d. Moreover, possible variations in plasma Brain Natriuretic Peptide (BNP) levels during the menstrual cycle have not been studied. We measured the pl asma levels of ANP and BNP by means of two highly sensitive and specific im munoradiometric assay (IRMA) methods in 19 normal women without premenstrua l symptoms, in order to evaluate whether significant modifications of these hormones are present during the menstrual cycle. Because it is well-known that circulating levels of cardiac hormones show great variations in normal subjects due to their rapid plasma half lifes, blood samples were collecte d at 2.5-min intervals over a 15-min period on the 5(th) and 24(th) days of the cycle. The mean (+/-SD) values of ANP (follicular phase=15.1+/-8.7 pg/ ml; luteal phase=14.8+/-9.5 pg/ml) and of BNP (follicular phase=13.0+/-15.0 pg/ml; luteal phase=11.2+/-11.4 pg/ml) did not show significant variations during the menstrual cycle. Moreover, the variability of ANP values (CV=24 .8+/-13.2%) was significantly higher (p=0.0318) than that of BNP values (CV =16.5+/-8.9%), and a significant correlation was found between the mean ANP and BNP values of the individual women studied (R=0.407, p=0.0437). The va lues of estradiol, progesterone, LH, FSH and prolactin did not correlate wi th the ANP or BNP values. In conclusion, our results indicate that circulat ing levels of cardiac hormones do not show any significant modifications du ring the menstrual cycle in healthy women; (J. Endocrinol. Invest. 22: 1-5, 1999) (C)1999, Editrice Kurtis.