Introduction
Definition
Menopause is part of the normal ageing process and will occur in all women who live long enough. The diagnosis is clinical. Natural menopause is a retrospective diagnosis that can only be made after 12 months of amenorrhoea, that is not associated with some other physiological (e.g.
lactation) or pathological cause and, in the United Kingdom, the mean age is 51 years.STRAW+10
Menopause occurs as a result of oocyte depletion in the ovary. This is associated with an increase in circulating follicle-stimulating hormone (FSH) and a decrease in circulating oestrogen. In 2001, the World Health Organization (WHO) and Stages of Reproductive Ageing Workshop (STRAW) Working Groups defined menopause as the permanent cessation of menstrual periods that occurs naturally or is induced by surgery, chemotherapy, or radiation.
WHO recommended the use of ‘perimenopause' and ‘menopausal transition' in place of ‘climacteric' in 1996 and a model was developed in 2001 to describe the stages of the menopausal transition. The model identifies seven stages of reproductive life and is primarily based on the characteristics of the menstrual cycle and secondarily, on follicular phase FSH concentrations in the circulation. The model was reviewed in 2011, STRAW+10, and has been recommended regardless of women's age, ethnicity, body size, or lifestyle characteristics (Figure 46.1).
As women progress through the menopausal transition, the menstrual cycle becomes irregular, and FSH levels are raised in response to decreased ovarian hormone concentrations, normally starting to rise around the age of 38. Menstrual cycles are then missed and ultimately stop, as does ovulation; however, the change in gonadotropins and sex steroids actually starts in the late 30s as the rate of decrease in the ovarian follicle numbers escalates. During the perimenopause, FSH levels can fluctuate considerably in response to spasmodic oestrogen production from the ovary.
Physiology
Figure 46.2 shows a rapid decrease in the number of primordial follicles after the age of 40 years. Fewer follicles result in decreased secretion of inhibin B, with a subsequent increase in FSH that can maintain oestradiol until follicle depletion. Levels of serum FSH begin to increase in women still having regular cycles.
Diagnosis
The recommendation from the National Institute for Health and Care Excellence (NICE) guideline, published in 2015, is to diagnose menopause clinically, on the basis of menstrual history and age. Biochemical measurements are not required in women who are over the age of 45 years. Vasomotor symptoms and irregular periods suggest perimenopause, while menopause may be diagnosed in women who have not had a period in at least 12 months.
NICE recommends measuring FSH levels in women who are between the age of 40 and 45 years, who present with symptoms, including a change in their menstrual cycle, and in women under the age of 40 years, in whom menopause is suspected (2).