The vasomotor symptoms of menopause are commonly known as hot flashes and night sweats. The majority of menopausal women in the West report experiencing these symptoms at least once.
They are among the most common reasons that women seek treatment of menopausal symptoms.
Menopause is defined as the permanent cessation of menstruation due to the loss of ovarian activity, and technically occurs twelve months after the last menstrual cycle. The time leading up to menopause, when ovarian activity is slowing and changing, is known as perimenopause.
Women who are more than twelve months past their last menstrual period are said to be in postmenopause. Menopause can occur naturally or as a result of radiation treatment, medication, or surgery such as oopherectomy or hysterectomy.
Physiology of Menopause
Several changes occur during perimenopause. Most apparent are changes in the menstrual cycle.
The time between menstrual periods usually becomes shorter, and the quality of menstruation may vary. The ovarian follicles (where eggs develop) decrease as the number of eggs declines.
Hormone levels change: follicle stimulating hormone (FSH), which signals the production of estrogen and progesterone, increases. Progesterone levels decrease throughout perimenopause.
Estrogen levels, in contrast, begin their decline in the last six to twelve months of perimenopause. Just before true menopause, they rise and then drop permanently.
Lower levels of estrogen cannot sustain the uterine lining, and so the period ceases.
Hot flashes are characterized by feelings of warmth that come on suddenly and pass quickly. They range from a mild flushed feeling to intense heat accompanied by sweating.
Some women, but not all, report triggers that bring on or increase hot flashes. Common triggers include stress; alcohol; caffeine; high temperatures; hot food or drinks; and spicy foods.
Flashes usually begin just after perimenopause and last anywhere from two to ten years. Frequency varies from a few times a year to several times a day.
Night sweats are hot flashes that occur during sleep. They are characterized by copious perspiration.
Some women report having to get up to change the sheets after such an episode. Sleep is disrupted as a result, adding to stress and fatigue the next day.
Causes of Vasomotor Symptoms
Although vasomotor symptoms occur at the same time as ovarian decline, the exact relationship between the two is not known. Such symptoms typically occur when the set point of the body's temperature suddenly changes, as occurs at the beginning and end of a fever, but the effects of estrogen on the set point remain mysterious.
Not all women with low estrogen experience hot flashes, and they are often experienced during pregnancy, a time when estrogen is very high. Women in several cultures experience no vasomotor symptoms at all, which seems to belie a purely physiological cause.
Consequences and Considerations
For many women, the vasomotor symptoms of menopause are a minor annoyance. For others, they cause significant disruptions to sleep, work and daily life.
Vasomotor symptoms can be a sign of several conditions besides menopause, including thyroid disease, epilepsy, several hormone-producing tumors, leukemia, and allergic disorders. If symptoms persist, worsen, or interfere with daily life, consult a qualified health practitioner for advice.