Age related changes in the female reproductive cycle

To investigate the effect of age on the control of the reproductive cycle in regularly menstruating women.

In this prospective study all women were seen regularly during both the follicular and luteal phases. Ultrasound scanning was used to confirm ovulation and measurements were taken to assess follicular development and endometrial thickness. Serum gonadotrophin levels on day 4 of the cycle, the maximum periovulatory oestradiol and progesterone on the seventh day after ovulation were measured and compared in different age groups.

Fifty-six healthy, regularly menstruating women were recruited from volunteers amongst staff of the University Hospital of South Manchester.

Ovulation occurred later in the cycle for older women, with mean follicular phase length increasing from 13.9 days (in group 21-25 years) to 15.9 days (in group 37-45 years (P < 0.05). The mean of the maximum follicular diameter prior to rupture was significantly smaller in the older women: 16.7 mm in the 37 to 45 years old group compared with 19.6 mm, 21.6 mm and 21.3 mm in the 21 to 25, 26 to 31 and 32 to 36 years old age groups, respectively (P < 0.001). The maximum thickness of the endometrium in the luteal phase was greatest for older women: 15.9 mm in the age group 37 to 45 years compared with 12.1 mm in the age group 21 to 25 years (P < 0.001). Serum gonadotrophin concentrations during menses were higher with increased age; mean follicle stimulating hormone was 4.8 iu/l in the age group 21 to 25 years, and 8.5 iu/l in the age group 37 to 45 years (P < 0.001). Mean luteinising hormone was 4.5 iu/l in age group 21 to 25 years and 7.21 iu/l in age group 37 to 45 years (P < 0.001). Mean ovarian steroid concentrations were no different.

These data illustrate significant age related differences in the pituitary-ovarian axis and endometrial thickness. This has implications for the management of older women in assisted reproduction and fertility control programmes.