Renal haemodynamics and extracellular homeostasis during the menstrual cycle

Abstract

Renal haemodynamics and extracellular homeostasis during the menstrual cycle were studied in 14 healthy women (age 21–41 years) who were not taking oral contraceptives in the follicular (Period I) and luteal phase (Period II). The glomerular filtration rate ([⁵¹Cr] EDTA clearance) and the effective renal plasma flow ([¹²⁵I] hippuran clearance) increased from Period I to II by a median of 6.3% (95% confidence interval (CI): 0.6–9.2%) and 7.3% (95% CI: -0.4–22%) respectively. Serum sodium decreased from period I to II (p<0.01) by a median of 1 mmol/l (95% CI: -2.0 to -0.5 mmol/l) and the urinary excretion rate of potassium increased (p<0.02) from a median value of 35 μmol/min in Period I to 45 μmol/min in Period II. The extracellular fluid volume did not change between the two periods but the concentration of water in serum increased (p<0.05) from a median value of 91.7–92.0 g/100 g in Period II. Serum total protein and serum albumin both showed a borderline statistically significant decrease from Period I to II. The investigation demonstrated a number of physiological and biochemical changes from the follicular to the luteal phase, most of which in a lower scale mimic well known changes that occur during pregnancy.

Key words:

• albumin
• effective renal plasma flow
• extracellular fluid volume
• glomerular filtration rate