Tibolone is a unique chemical compound that provides an alternative to conventional hormone therapy (HT) for the treatment of postmenopausal women who are experiencing symptoms due to lack of oestrogen. These may include hot flushes, night sweats, vaginal dryness, disturbed sleep, mood swings and loss of interest in sex.
How does tibolone work?
Tibolone itself has very weak actions in the body. However after being taken, tibolone is partly activated in the gut and then released into the blood stream. Final activation of tibolone occurs in the “target tissues” such as the brain, bone, uterus and so forth.
The unique feature of tibolone is that different tissues in the body activate tibolone in different ways. Therefore in the brain, bone and vagina tibolone is activated to an oestrogen-like form. This is how tibolone stops hot flushes, prevents bone loss and treats vaginal dryness.
In contrast in the uterus tibolone is converted to form that behaves more like progesterone, which protects the lining of the uterus so bleeding does not occur..
Tibolone can also be converted to a form which has weak testosterone action. As a result, women may experience an improvement in mood and in sexual interest when they take tibolone.
Tibolone appears to have neutral effects in the breast. Therefore it is uncommon for women taking tibolone to experience breast tenderness.
Who would benefit from tibolone?
Tibolone will reduce flushes and sweats, improve vaginal dryness and sleep in most women experiencing these symptoms after menopause.
It is recommended that for a woman who has not had a hysterectomy, tibolone not be taken until she has had 12 months without a normal menstrual bleed.
Women who have had a hysterectomy and are experiencing menopausal symptoms can start tibolone when they have menopausal symptoms.
Tibolone should not be taken in combination with other hormone therapy. It should not be combined with testosterone.
Although not specifically approved for the treatment of osteoporosis, there is evidence that tibolone prevents postmenopausal bone loss, particularly from the spine, after menopause and prevents postmenopausal fractures.
In postmenopausal women tibolone may improve sexual desire, arousal and satisfaction.
What is the dose?
Tibolone comes as a 2.5 mg tablet. However studies have shown that half a tablet (1.25mg) can be effective to prevent bone loss and fractures in older women. Many women find 1.25 mg enough to treat their flushes and sweats. It is quite reasonable to start with half a tablet daily but the dose should never exceed one tablet daily.
Are there any side-effects or risks with tibolone?
- Occasionally women report fluid retention and mild weight gain with tibolone- if this occurs it is reasonable to try taking half a tablet (1.25 mg) each day.
- Vaginal bleeding or spotting may occur in women just after commencing tibolone, however this is uncommon.
- In large carefully conducted clinical studies tibolone has not been shown to increase the risk of thrombosis (blood clots), heart attack or cancer of the uterus.
- In contrast to oestrogen and progestin therapy, tibolone does not adversely affect the appearance of mammograms and is not associated with an increased likelihood of breast tenderness.
- Tibolone may lower the production of a protein that carries thyroid hormone in the blood stream. After starting tibolone women taking thyroid hormone supplements should have their thyriod hormone levels checked after about 6-8 weeks.
- Tibolone reduces the liver production of a protein called sex hormone binding globulin (SHBG). SHBG binds testosterone so lower SHBG levels means that more testosterone is free in the circulation and can act in cells. For women with low to normal testosterone levels this effect may contribute to enhanced sexual function with tibolone therapy. However, the lowered SHBG may result in androgenic side effects like acne and increased hair growth in a small number of women.
- Although tibolone is mostly mood enhancing, occasionally women experience depressed mood on tibolone. This is possibly due to it progestogenic effects.
- In the LIFT study (a study of the use of tibolone to prevent fractures in women over 60 years) an increase in the risk of stroke was reported. This effect is similar to that seen for women who commence oestrogen over the age of approximately 60 years.