Differences in decline in GFR with age between males and females. Reference data on clearances of inulin and PAH in potential kidney donors

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Abstract
Background. To ensure that potential kidney donors have no renal impairment, it is extremely important to have accurate methods for evaluating the glomerular filtration rate (GFR). The golden standard, clearance of inulin, has been used in the present study. The aim was to evaluate the effects of age and sex on renal function and present reference data. Methods. A total of 122 potential kidney donors, 62 females, aged 21–67 years, were investigated with the GFR and effective renal plasma flow (ERPF) determined by clearances of inulin and para-amino hippurate. Results. The mean ± SD GFR and ERPF were 105 ± 13 and 545 ± 108 ml/min/1.73 m 2 , respectively, and we found no difference between the males and females. When relating GFR and ERPF to age, however, a significant decline was found in GFR and ERPF in males, but not in females in the age range of 20–50 years. GFR fell by a mean of 8.7 ml/min/1.73 m 2 and ERPF by 90 ml/min/1.73 m 2 per decade in male donors. Conclusion. With adequate methods for determining GFR and ERPF, a clear difference in the effect of age was seen between the sexes. Males showed a significant decrease between 20 and 50 years of age, which was not seen in females. Females seem to be protected in the pre-menopausal period probably by oestrogens. These results confirm clinically those found in rats.