Chapter 105: The menopause

INTRODUCTION

DEFINITIONS

The WHO has defined the menopause as signifying the permanent cessation of menstruation, resulting from the loss of ovarian follicular activity.² In most Western women, it occurs between the ages of 45 and 55 years, with an average age of 51.5 years.¹ Premature menopause (or premature ovarian insufficiency) is menopause occurring before age 40, while early menopause occurs before 45.

The term is used in a broader sense to include the perimenopausal phase when ovarian function waxes and wanes and the periods become irregular. This may last 2–5 years and sometimes longer and involves the premenopausal and menopausal phases.

The postmenopause is the period following the menopause but cannot be defined until after 12 months of spontaneous amenorrhoea, except in women who have had an oophorectomy.

Surgical menopause is known as bilateral oophorectomy.

Summary

The climacteric can be subdivided into four phases:

Phase 1 Premenopausal: up to 5 years before the last menstrual period.

Phase 2 Perimenopausal: the presence of early menopausal symptoms with changes in menstrual cycle.

Phase 3 Menopausal: the last menstrual period.

Phase 4 Postmenopausal: the phase beginning 12 months after the last menstrual cycle.

Osteoporosis

Osteoporosis, which literally means porous bone, is reduced bone mass per unit volume. Osteoporosis is usually addressed in the context of the menopause because the drop in oestrogen levels causes accelerated loss of bone mass (10% the first 5 years after menopause). Loss of bone density can be largely prevented by correcting oestrogen deficiency.

PHYSIOLOGY OF THE MENOPAUSE

FIGURE 105.1 provides an overview of how menopausal symptoms are related to ovarian follicular activity and hormonal activity.

Women are born with their total complement of ovarian primary follicles. The peak number is reached at about 20 weeks’ gestation, while in their mother’s womb, with an average number of 6 million. From this point, a female constantly loses gametes, reaching 1 million at birth and about 400 000 by puberty. A woman will ovulate 400–500 times in her lifetime and will begin the menopause transition when there are only a few thousand follicles remaining.

The number of follicles declines rapidly as the menopause approaches, with an insufficient number to stimulate cyclical activity. Oestrogen levels fall and this has a positive feedback on the pituitary, increasing ...