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MOH strengthens warnings over use of HRT

Media Release

17 November 2003

Ministry of Health strengthens warnings over use of HRT

The Ministry of Health has strengthened its caution to health professionals and women about the use of hormone replacement therapy. This follows a review of recent studies clarifying the risks associated with use of these medicines.

The new advice leads on from earlier statements made by the Medicines Adverse Reactions Committee, MARC, which is an independent expert advisory committee on medicines safety. The advice is:

Women should be advised of the risks associated with use of hormone replacement therapy (HRT) before treatment begins. Including information that use of HRT is associated with increased risk of developing blood clots in the veins of the legs and in the lungs (pulmonary embolism), stroke (bleeding or blood clot in the brain) and breast cancer. These risks exist for all forms of HRT and increase with duration of use. While the increased risk of developing a blood clot appears within a few weeks of starting treatment, other risks only become evident after longer use, with the increased risk of developing breast cancer appearing after 1-2 years use of HRT. Many of the risks associated with use of HRT also increase with age and for women aged 65 or older HRT use is associated with an increased risk of dementia.

Due to the publication of the Million Woman study which showed that the increased risk of breast cancer appears within 1-2 years, the MARC now recommend that where HRT is prescribed, it should be taken at the lowest dose for the shortest period of time. The need for continuing treatment should be reviewed six-monthly.

HRT should no longer be used for the primary or secondary prevention of cardiovascular disease (heart attack or stroke). It remains an appropriate treatment only for women with moderate to severe menopausal symptoms such as hot flushes and sweats.

"Two new studies examining the safety of HRT have provided important new information about the safety of both combined HRT and oestrogen-only HRT since the Medicines Adverse Reactions Committee issued advice in September 2002," said Medsafe's Principal Advisor, Dr Stewart Jessamine.

A large scale US based study of 16,000 women, The Women's Health Initiative Memory Study (WHIMS), further discredited use of HRT in older women when it found combined HRT doubled the risk of developing dementia. The study estimated that use of combined HRT in women aged 65 years and over would produce an extra 23 cases of dementia per 10,000 women per year, with the increased risk becoming noticeable after one year of combined HRT treatment.

An extremely large study in the United Kingdom, The Million Women Study, presented significant new information including:

- the risk of breast cancer is seen within one to two years of commencing HRT and increases with duration of use,

- all forms of HRT are associated with an increased risk of developing breast cancer,

- the risk of breast cancer decreases after stopping HRT, and within five years the residual risk is not significantly different from that observed for women who have never used HRT.

Dr Jessamine said "The risk of developing breast cancer associated with HRT use is relatively small, causing an additional 6 breast cancers per 1000 women after 5 years use of HRT. However, in the opinion of the MARC, the studies all demonstrate that the risks of HRT treatment outweigh the benefits for everything other than for short-term use to relieve moderate to severe symptoms caused by the menopause. The new evidence supports the conclusion that if HRT is required, it should be used for the shortest period of time possible. Prescribers should be actively monitoring patients on HRT a minimum of every six months to make sure ongoing treatment is really necessary."


What risks did the studies show?

Table 1. Number of additional breast cancers from HRT use (compared to no HRT use) per 1000 women by age 65 from The Million Women Study.

Table 2. Summary of incidence of adverse events based on results from the WHI study. Data derived from women aged 50 to 79 years, after an average follow-up of 5.2 years.

Adverse Event

Change in number of
adverse events per 10,000
women in one year

Breast cancer
8 extra

Heart disease
7 extra

8 extra

Pulmonary embolism
8 extra

Colorectal cancer
6 fewer

Hip fracture
5 fewer

How is this advice different from the previous advice?

The new advice says the need for continuing treatment should be reviewed six-monthly, and HRT should be taken at the lowest dose for the shortest period of time. The September 2002 advice said HRT should be reviewed at the time of the next prescription.

How significant are the risks?

The absolute risk of developing breast cancer, heart disease, stroke and pulmonary embolism associated with HRT use is small (31 extra cases per year in 10,000 women over 50 years of age using HRT long term). Note these are cases, not deaths.

What are the increased risks of dementia?

Combined HRT doubled the risk of developing dementia, which would result in an extra 23 cases of dementia per 10,000 women per year.

What are the benefits of HRT?

The therapy can alleviate symptoms of menopause including hot flushes, and sweats. The studies showed that HRT was protective for colorectal cancer and hip fracture (11 fewer cases per year per 10,000 women over 50 years of age using HRT long term).

How does it work?

The body's production of two hormones decreases when a woman reaches menopause. Those hormones are oestrogen and progestogen and the replacement therapy aims to replace one or both of those hormones.

How is it administered?

In New Zealand, most women take HRT in tablet form. A very few use patches.

If I'm concerned, what should I do?

Talk with your doctor about whether you should continue with HRT. If a decision is made to stop HRT it should be withdrawn gradually. Information on how to reduce HRT can be found in the 2002 HRT Guideline Update on the New Zealand Guidelines Group website:

Where can I find information about this advice and the studies it refers to?


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