What are hot flashes in menopause?

What Are Hot Flashes in Menopause?

Hot flashes are recurrent, transient episodes of flushing, perspiration, and a sensation ranging from warmth to intense heat on the upper body and face, sometimes followed by chills, lasting 1-5 minutes. 1, 2

Clinical Definition and Characteristics

Hot flashes are classified as vasomotor symptoms along with night sweats (which are hot flashes occurring with perspiration during sleep). 1

Physical Manifestations

• Core body temperature increases by approximately 0.5°C during an episode 3
• Skin temperature rises by 0.25-3°C 3
• Episodes involve flushing, sweating, and a sensation of intense heat primarily affecting the upper body and face 1, 4
• May be followed by chills after the heat sensation subsides 1
• Duration is typically 1-5 minutes per episode 2

Underlying Pathophysiology

The mechanism involves dysfunction of central thermoregulatory centers in the hypothalamus triggered by estrogen level changes at menopause. 5, 6

Key Mechanisms

• Narrowing of the thermoneutral zone (TNZ) in symptomatic women, making them hypersensitive to minor core temperature elevations 3, 6
• Small elevations in core body temperature (as little as 0.5°C) trigger the vasodilatory response within this narrowed zone 6
• Elevated central noradrenergic activation contributes to the narrowed thermoneutral zone 6
• Recent evidence implicates the neurokinin B (NK3) receptor pathway in the hypothalamus as a key mediator 7
• Additional neurotransmitter systems involved include calcitonin gene-related peptide, hypothalamic kisspeptin, serotonin, and norepinephrine 2

Important Clinical Note

Estrogen levels do not differ between symptomatic and asymptomatic postmenopausal women—the issue is the change in estrogen levels and individual sensitivity to this change, not absolute levels. 6

Epidemiology and Impact

• Affect 50-85% of postmenopausal women over age 45 3
• Approximately three-fourths of postmenopausal women experience hot flashes 5
• Symptoms can be more severe in women with breast cancer compared to naturally menopausal women 1
• Only a minority seek treatment despite significant impact on quality of life 2

Triggers and Aggravating Factors

Common triggers include: 8

• Spicy foods
• Hot environments and hair dryers
• Alcohol (variable individual response) 1

Aggravating factors: 8

• Obesity/overweight status
• Smoking
• Stress

Special Populations

Breast Cancer Patients

Hot flashes in breast cancer survivors have multiple potential causes: 1, 8

• Natural menopause coinciding with cancer diagnosis
• Abrupt cessation of hormone therapy at diagnosis
• Chemotherapy-induced ovarian dysfunction (temporary or permanent) 1
• Endocrine therapy (tamoxifen, aromatase inhibitors) 1
• Surgical menopause from bilateral oophorectomy (>90% experience hot flashes) 1

Surgical Menopause

Women undergoing bilateral oophorectomy experience particularly severe and long-lasting hot flashes due to the sudden, complete drop in estrogen levels rather than gradual decline. 1, 4

Clinical Significance

Hot flashes represent one of the most common health problems in postmenopausal women, causing: 5

• Sleep disturbance
• Impaired daily function
• Reduced quality of life
• Significant healthcare costs and lost productivity 7
• May serve as a harbinger for future disease risk 7

Practical Management Considerations

Lifestyle modifications that may help: 8

• Dressing in layers for easy removal during episodes
• Avoiding overheating
• Using natural fiber clothing
• Applying cold compresses intermittently
• Keeping a symptom diary to identify personal triggers 8

For many women, hot flashes improve with time, and studies demonstrate a marked placebo effect with interventions. 8