Hormone Replacement Therapy
Examples
- Oestrogen
- Oestrogen with progestogen
Indications
- Treatment of menopausal symptoms
Although HRT can reduce osteoporosis, this is not an indication for therapy alone.
Contraindications
Contraindications
- Oestrogen-dependent cancer
- History of breast cancer
- Thrombophlebitis
- Thromboembolism
- Liver disease
Cautions
- Migraine
- Diabetes
- Risk factors for oestrogen dependent tumours (including breast cancer)
- Risk factors for thromboembolism
Mechanism
Exogenous administration of oestrogen replaces the lack of endogenous oestrogen during and following menopause or hysterectomy, acting to reduce vasomotor effects. When the uterus remains present the addition of progesterone is necessary to decrease the risks associated with unopposed oestrogen (aggravation of existing endometriosis, risk of endometrial cancer).
Administration
A wide range of products are available and can be given by various routes (oral, topical - patches / gel, nasal Spray, implants).
The CSM advises that the minimum dose of HRT should be given for the shortest possible time to reduce risks.
Adverse Reactions
- Hypertension
- Painful breasts
- Endometrial bleeding
- Impairment of glucose tolerance
- Migraine
Interactions
Enzyme inducing drugs e.g. phenytoin, carbemazepine, rifampicin, griseofulvin can induce metabolism of HRT, but is unlikely to be problematic.
Education
Patients should be informed about the risks of thromboembolism and breast cancer whilst on HRT. Patients should also be warned that HRT is not a contraceptive and pregnancy may be possible for some time peri-menopausally.
Pharmacokinetics
Oestrogens and progestogens are lipophilic steroid hormones, which are completely absorbed from the gastrointestinal tract when taken orally. They are metabolised by the liver and their metabolites are then excreted in the bile. The breakdown products are taken back up when in the intestine providing a constantly renewed pool of components for the production of oestrogen and progestogen. Oestrogen metabolites and conjugates are excreted in the urine.
Topically applied oestrogens and progestogens enter the systemic circulation over a greater period of time.
