Hot flushes

Hot flushes are due to vasomotor instability and are usually related to the female menopause, though pathological causes should also be considered.

What causes hot flushes?

Hot flushes are thought to be related to changes in central nervous system neurotransmitters and peripheral vascular reactivity. There is still much that is not understood. The aetiology of hot flushes in menopause would seem to be related to low oestrogen levels as the ovaries fail and the effect on central thermoregulation. Many women are thought to try to manage their symptoms without seeking professional advice.

They do not tend to occur in men, as there is not a similar rapid decline in hormones. However, treatment for prostate cancer that involves suppression of testosterone production can produce a picture similar to menopausal hot flushes in women and can be just as severe.

How common are hot flushes? (Epidemiology)

• Reported prevalence varies greatly between studies.

• These symptoms are experienced by around 80% of menopausal women.

• Frequent menopausal vasomotor symptoms (including hot flushes) persist in more than half of women for more than seven years.¹

• Hot flushes can also occur in younger women with premature ovarian insufficiency.

• A cohort study of US women reported that vasomotor symptoms were more prevalent among African-American and Hispanic women, and less prevalent among Japanese and Chinese women, with the lowest reported prevalence among non-Hispanic white women.²

Risk factors

• They tend to be more severe in women of low body weight, those who take little or no exercise and those who smoke cigarettes.

• Flushes last for fewer years when they are first felt after the cessation of menstruation.¹

• There is variation in frequency and duration between different races. Japanese women seem to have a particularly low incidence of hot flushes. In the USA, women of Afro-Caribbean origin have been shown to have flushes which last for more years than those of white women.^{1 3}

• An abrupt or early menopause causes more severe symptoms. Thus, surgical oophorectomy or its equivalent induced with chemotherapy, radiation or drugs produces more pronounced symptoms than a natural menopause.

Symptoms of hot flushes ²

There may be a history of menstruation becoming irregular or ceasing but not necessarily. There may have been surgery, radiotherapy or chemotherapy, involving removal or inactivation of the ovaries. Similar causes of sudden withdrawal of sex hormones in men produce a similar response.

Hot flushes and night sweats substantially increase in frequency and severity during the menopausal transition and are most common in the first year following the last menstruation.

• Hot flushes may last between a few seconds and 10 minutes but an average is around 4 minutes. Frequency may be from every hour to a couple of times a week.

• Hot flushes commonly affect the face, head, neck and chest.

• There is a sensation of intense heat and a feeling that the face and whole body are flushing. It is often difficult to ignore and women having hot flushes often fling open windows when all around them are anything but warm. Flushing and sweating may not be apparent to the observer but the person affected tends to be very self-conscious of the affliction.

• Lack of concentration and poor memory are commonly associated with hot flushes.

• Sleep disturbance is common with night sweats.

• Features of depression are not unusual.

• Having frequent flushes and disturbance of sleep may be a major contributor to the commonly observed adverse effect on mood.

• Inappropriate vasodilatation leads to a slight drop in core temperature. Between attacks there is no abnormality to be found.

Differential diagnosis

Other causes of flushing to consider:

• Hyperthyroidism.

• Carcinoma of the pancreas.

• Carcinoid tumours.

• Phaeochromocytoma (may be part of a multiple endocrine neoplasia syndrome).

• Brain tumours and spinal cord lesions (can lead to vasomotor instability).

• Panic disorder.

• Tuberculosis.

• Diabetes insipidus.

• Frey's syndrome (flushing when the affected person eats, sees, thinks about or talks about certain kinds of food which produce strong salivation; may occur as a complication of parotid gland surgery).

• Some food substances - eg, monosodium glutamate.

• Some drugs - for example:

  • Nitrates.

  • Calcium-channel blockers.

  • Selective serotonin reuptake inhibitors (SSRIs).

  • Levodopa.

  • Selective (o)estrogen receptor modulators (SERMs) such as raloxifene and tamoxifen.

  • Anti-androgens such as cyproterone, spironolactone, bicalutamide, 5-alpha-reductase inhibitors.

  • Danazol.

  • Goserelin.

Investigations

Laboratory tests are not required in the following otherwise healthy women aged over 45 years with menopausal symptoms:⁴

• Perimenopause based on vasomotor symptoms and irregular periods.

• Menopause in women who have not had a period for at least 12 months and are not using hormonal contraception.

• Menopause based on symptoms in women without a uterus.

Follicle-stimulating hormone (FSH) levels should be undertaken in suspected premature ovarian insufficiency.

Treatment for hot flushes²

Hot flushes do not threaten life but they can have a very detrimental effect on the quality of life. They will subside with time but a sympathetic, positive approach is required.

Lifestyle changes

The following lifestyle advice should be given:

• Take regular exercise - a systematic review found that exercise may improve vasomotor symptoms, although the certainty of evidence is low. ⁵

• For women with overweight or obesity, weight loss may improve symptoms.

• Wear lighter-weight clothing and sleep in a cooler room.

• Avoid possible triggers, such as spicy foods, caffeine, smoking, stress and alcohol. It is worth always asking about alcohol intake, as a cause of hot flushes and for general health promotion reasons.

Pharmacological treatments

Hormone replacement therapy (HRT)
Hormone replacement therapy (HRT) is the most effective treatment to relieve the symptoms caused by the menopause. HRT can be offered for vasomotor symptoms after discussing the short-term and longer-term benefits and risks.

See the separate Hormone replacement therapy (including benefits and risks) article for details.

Alternative pharmacological treatments to HRT ²
Some women consider alternatives to HRT to combat climacteric symptoms. They may not want to take HRT, or have contra-indications to taking it.

These may include:

• SSRIs and venlafaxine - effective for vasomotor symptoms in some women but their effect is often short-acting, and their use for this is unlicensed.

• Clonidine - evidence is limited but anecdotally this works for some women, and it has a licence for this indication. ; side-effects such as dry mouth and tiredness can be a problem. Clonidine works by widening the thermoneutral zone. A trial of 2-4 weeks is required and it should be stopped if there is no benefit, as benefits do not accrue over time.

• The anticonvulsant gabapentin, also unlicensed.

The National Institute for Health and Care Excellence (NICE) recommends that clinicians should not routinely offer SSRIs, serotonin and norepinephrine reuptake inhibitors (SNRIs), or clonidine as first-line treatment for vasomotor symptoms alone.⁴

Alternative therapies for hot flushes

• Menopause specific cognitive behavioural therapy has been shown to be effective for some women.

• There is no evidence that acupuncture improves hot flushes more than sham acupuncture or placebo, nor is there any evidence for relaxation techniques. ^{67 89}

• Phyto-oestrogens - naturally occurring compounds found in plant sources and structurally related to estradiol. Foods such as soy beans, as well as nuts, wholegrain cereals and oilseeds, are the foods most rich in phyto-oestrogens. Phyto-oestrogens can also be taken in the form of tablets containing concentrated isoflavones, such as red clover. Data in this area is variable, although some studies show that black cohosh is effective in reducing hot flushes. These preparations should not be used in women who have had breast cancer.¹⁰¹¹

Many women choose to try these products, as they believe them to be safer and more 'natural' than prescribed medication. However, most herbal products available in the UK are not subject to the same regulatory requirements as licensed medications and, as such, are not subject to the same degree of standardisation. There may be variability between products or a lack of clarity as to what ingredients a particular product contains and uncertainty about potential serious interactions with other drugs (including tamoxifen, anticoagulants and anticonvulsants).

In addition, there is currently insufficient evidence to suggest that they are safe to be taken by women with oestrogen-dependent cancer - eg, breast cancer. There are no safety data available in relation to their risk of venous thromboembolism (VTE). If a woman wants to use such preparations, she should be advised to look for one that has the MHRA approved traditional herbal medicine logo. ¹²

Prognosis²

• Symptoms typically last for 5-7 years, but some women continue to experience symptoms for at least 10-15 years.

• A large US longitudinal observational study found that vasomotor symptoms persisted for a median of 7.4 years.

• Persistent vasomotor symptoms may be associated with ethnicity, younger age at menopause, current smoking, weight gain, and lower educational level.