Difference of LH and FSH secretory characteristics and degree of concordance between postmenopausal and aging women

OBJECTIVE: Several neuroendocrine changes occur at menopause and the present study aimed to verify whether the episodic release and the degree of concordance of LH and FSH differs between early and late postmenopausal women. METHODS: Postmenopausal (n = 32) women were enrolled and subdivided in two groups according to the menopausal age: group A (n = 22), patients with more than 2 but less than 5 years from the occurrence of menopause; group B (n = 10), patients with more than 15 years from the occurrence of menopause. All subjects underwent a pulsatility study (4 h, sampling every 10 min) to assess LH and FSH secretory characteristics and their degree of concordance. RESULTS: Mean +/- S.E.M. LH and FSH plasma levels were lower in older women than in postmenopausal women (P < 0.01). The secretory pattern was pulsatile for both LH and FSH and their pulse amplitudes were lower in aged women (P < 0.01). No significant difference was observed in terms of pulse frequency between the two groups. LH and FSH pulses were co-secreted in early postmenopausal women while such a concordance was lost in older women. CONCLUSIONS: Late postmenopause is characterized by the reduction of the amplitude of gonadotropin pulses in comparison to women in early postmenopause, reflecting changes of both GnRH secretion and/or pituitary responsiveness to GnRH. The age-related loss of concordance between LH and FSH pulses discloses the existence of a hidden FSH stimulating system, which drives FSH episodic release independently and more promptly than GnRH.