The menopause transition: endocrine changes and clinical symptoms.

Several biological changes take place during the menopause transition. The number of oocytes declines progressively from before birth but reaches a critically low level by the time of the menopause. The regular pattern of the menstrual cycle becomes disrupted and the frequency of normal ovulatory cycles declines. Rising gonadotrophin levels, particularly of follicle stimulating hormones (FSH), and declining estrogen levels are thought to characterize the menopausal transition. It now appears that declining levels of inhibin may play an important role in maintaining estrogen levels until just before the menopause, while causing increased levels of gonadotrophins. Wide variations in hormonal profiles between and within individuals occur. The clinical responses to this endocrine instability include vasomotor symptoms, psychological symptoms, sexual dysfunction and irregular menstrual bleeding. Estradiol deficiency induces a rapid phase of increased bone turnover in the early postmenopausal period, which can contribute to osteoporosis later in life. Similarly, changes in lipid profiles, particularly high-density lipoprotein (HDL) and triglycerides, can also occur.