Endocrinology: Vasopressin and atrial natriuretic hormone response to hypertonic saline during the follicular and luteal phases of the menstrual cycle

We studied the hormonal responses to hypertonic saline duringthe follicular (days 2–9) and luteal (days 21–28)phases of the menstrual cycle in nine healthy young women, aged19–25 years. On both study days, each woman was infusedwith 5% hypertonic saline for 1 h at the rate of 0.1 ml/kg/min.Serum progesterone and oestradiol concentrations confirmed thereported stage of the menstrual cycle. No difference in weightor haematocrit was observed between the two stages of the studyfor each woman. Baseline blood pressure, serum sodium, plasmaosmolality, plasma vasopressin and thirst levels were almostidentical for both stages, and changed to the same degree duringinfusion of hypertonic saline. Baseline atrial natriuretic hormoneconcentrations were higher during the follicular phase and becamesignificantly higher than during the luteal phase followinginfusion of hypertonic saline. We concluded that the intravascularvolume during the luteal phase may be effectively decreasedin comparison to the follicular phase.