Hormone Replacement Therapy (HRT)

HRT consists of oestrogen and progesterone replacement, using natural oestrogens derived from horse urine, and progestogens:

oestradiol
oestrone
oestriol.

Conjugated oestrogens is the term given to a combination of natural oestrogens. There are synthetic oestrogens available, these are:

ethinyloestradiol
mestranol
diethylstilboestrol.

Progesterons includes:

progesterone
didrogesterone
hydroxyprogesterone
medroxyprogesterone
norgestrel and derivatives.

Progestogens are normally prescribed with oestrogens as a tablet to be taken in the second half of the monthly cycle, because oestrogens cause the womb-lining to overthicken if taken on their own and this carries a high risk of cancer. These hormones are supplied in much larger amounts than the body's natural (endogenous) production, to offset losses through digestion and tissue dispersal.

How HRT Works

HRT preparations replace endogenous (a woman's own) hormones. They act on peripheral tissues (target cells) in the same way as described on page 18, but they send negative feedback to the hypothalamus, which reduces the production of releasing and stimulating factors. Side effects occur because they are given in higher doses than endogenous hormones and they disrupt the fine-tuning of the positive and negative feedback processes.

HRT Brands

The main brands of HRT (oestrogen and progestogen combination) are:

Premique
Climagest
Cyclo-progynova
Elleste.

These consist of separate tablets which are taken at different times in the monthly cycle to mimic the normal increase in progesterone in the second half of the cycle. The quantities of oestrogen contained vary by up to 100% between brands of tablets.

Patches

Patches are a type of plaster applied to the skin and which contain female hormones. They are more uniform, releasing much smaller amounts of oestrogens over a longer period. These don't pass through the digestive system, so this method is closer to the body's natural production of hormones. However progestogen has to be prescribed in tablet form to accompany oestrogen patches. Common brand names are:

Estrapak
Femapak
Evorel.

Each pack contains two types of patch, one for each half of the cycle, and the pack also contains progesterone tablets.

Post-Hysterectomy

Women who have had their womb removed (hysterectomy) can also choose from a range of oestrogenonly preparations, both patches and tablets. Brand names include:

Climaval
Elleste-solo
Estraderm
Fematrix
Menorest
Progynova.