What’s the latest on tibolone, the estrogen alternative?
the Way, Doctor
the latest on tibolone, the estrogen alternative?
(This article was first
printed in the April, 2004 issue of the Harvard
Women’s Health Watch. For more information
or to order, please go to http://health.harvard.edu/women.)
Q What happened
to tibolone — the estrogen alternative
we heard about a while ago? Did it turn out
not to be effective?
A When we first
wrote about tibolone in December 2001, many
experts anticipated FDA approval within a year
or two. That hasn’t happened, and you’re
not alone in wondering why.
Few things work as well as
estrogen-based therapy for relieving menopausal
symptoms, but many women prefer to avoid it
because of the health risks. Combined with
progestin (as Prempro), estrogen increases
a woman’s risk of cardiovascular events
and breast cancer. Taken alone, estrogen raises
the risk of uterine cancer and, to a lesser
extent, breast cancer.
Tibolone is a synthetic steroid
whose hormonal effects are said to be “tissue-specific” and
thus less risky than estrogen-based therapies.
Like estrogen, tibolone protects bone, alleviates
hot flashes, and improves vaginal tissues.
But it has a protective, progesterone-like
effect on the uterus, and it doesn’t
increase breast density or tenderness. Tibolone’s
cardiovascular effects are murkier. On the
positive side, the drug reduces total cholesterol
and harmful triglycerides and slightly lowers
LDL (bad) cholesterol. But it also lowers HDL
(good) cholesterol. Many experts are concerned
about this mixed picture.
maker, has undertaken several large randomized
studies to further evaluate the drug’s
safety and to assess its effects on fracture
risk. In all, more than 10,000 women will participate
in these trials.
Since tibolone is used in
70 other countries, why isn’t it available
in the United States? The answer lies in the
lessons learned from the Women’s Health
Initiative’s test of Prempro. Without
large randomized clinical trials, assessing
a drug’s safety and effectiveness is
a calculated shot in the dark. Given what we’ve
learned from hormone therapy’s long history,
it makes sense that FDA approval awaits further
data. It’s also worth noting that the
United Kingdom’s Million Women Study
found an increased risk of breast cancer in
users of all types of hormone-related therapies,
including tibolone (The Lancet, Aug.
— Celeste Robb-Nicholson,
Editor in Chief, HWHW