Hypothalamic-pituitary ageing: progressive increase in FSH and LH concentrations throughout the reproductive life in regularly menstruating women

Reproductive ageing is associated with reduced fertility and endocrine changes that become more pronounced during the perimenopausal period. We aimed to assess changes in gonadotrophin concentrations and the onset of these changes during the reproductive life prior to the perimenopause.

Ovarian and pituitary hormones were measured and follicle growth monitored in 500 regularly cycling infertile women aged 20-44 years.

Serum levels of FSH and LH were determined during the follicular phase and ultrasonography was used to monitor follicle growth and ovulation. The luteal phase was assessed by salivary progesterone measurements. Changes in basal FSH and LH with age during ovulatory cycles were assessed.

There was a significant progressive increase in FSH levels as early as age 29-30 years which was continued throughout the 30s and became more marked in the early 40s. LH levels showed significant increase at the age of 35-36 years which was maintained till the age of 40 years and followed by a further increase in women aged > 40 years.

An increase in FSH and LH concentrations can be detected in women with regular ovulatory cycles quite early during the reproductive life. The increase in basal FSH (and later LH) may represent the earliest endocrine marker of reproductive ageing. These age-related increases in FSH and LH can be used as hormonal markers to counsel patients as to the likelihood of their reproductive potential.