Hormone replacement therapy
Hormonal Replacement Therapy is a medical treatment containing estrogen, progestogen or both. Progetogen is added to the preparation for women with an intact uterus.
Indications for HRT include:
- Onset of the menopause
- Vaginal Atrophy
- Premature Ovarian Failure
Mode of Action 
This is almost entirely related to the function of estrogen. HRT's primary function is to reverse the effects a decrease in blood estrogen has on the body.
While estrogens are present in both men and women, they are usually present at significantly higher levels in women of reproductive age. They promote the development of female secondary sex characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle. In males estrogen regulates certain functions of the reproductive system important to the maturation of sperm and may be necessary for a healthy libido. Furthermore, there are several other structural changes induced by estrogen, in addition to other functions.
* Structural o promote formation of female secondary sex characteristics o accelerate height growth o accelerate metabolism (burn fat) o reduce muscle mass o stimulate endometrial hyperplasia - progestogen may be added to counteract this effect o increase uterine growth o maintenance of vessel and skin o reduce bone resorption, increase bone formation o morphic change (endomorphic -> mesomorphic -> ectomorphic) * protein synthesis o increase hepatic production of binding proteins * coagulation o increase circulating level of factors 2, 7, 9, 10, antithrombin III, plasminogen o increase platelet adhesiveness * Lipid o increase HDL, triglyceride, height growth o decrease LDL, fat depositition * Fluid balance o sodium and water retention o increase growth hormone o increase cortisol, SHBG * gastrointestinal tract o reduce bowel motility o increase cholesterol in bile * Melanin o increase pheomelanin, reduce eumelanin * Cancer o support hormone-sensitive breast cancers * Lung function o promotes lung function by supporting alveoli.
On the other hand, sexual desire rather depends on androgen levels than for estrogen levels.
The continuous combined regimen should only be used in patients who have had:
- A hysterctomy
- No history of endometiosis
- No menstrual periods in the last 12 months
The sequential regimen should be used for everyone else requiring or requesting HRT.
Advantages and Disadvantages of Different Modes of Delivery 
|Mode of Delivery||Advantages||Disadvantages|
|Patches||Avoid first pass in liver||Expensive
|Implants||Good Compliance||Half-yearly visits to the doctor
Difficult to use for some
Difficult to use for some
Relatively easy to use
The contraindications for HRT are absolute and include:
- Breast or endometrial cancer
- Undiagnosed vaginal bleeding
- Vascular disease
- Abnormal liver function test
Risks Vs. Benefits 
- ^ http://www.scienceblog.com/community/older/1997/B/199701564.html
- ^ http://www.sciencenews.org/pages/sn_arc97/12_6_97/fob1.htm
- ^ http://www.phimr.monash.edu.au/news/media_releases/estrogen_vital_for_male_sex_drive.htm - 20k
- ^ Massaro D, Massaro GD (2004). "Estrogen regulates pulmonary alveolar formation, loss, and regeneration in mice". American Journal of Physiology. Lung Cellular and Molecular Physiology 287 (6): L1154-9. PMID 15298854 url=http://ajplung.physiology.org/cgi/content/full/287/6/L1154.
- ^ Warnock JK, Swanson SG, Borel RW, Zipfel LM, Brennan JJ. (2005). "Combined esterified estrogens and methyltestosterone versus esterified estrogens alone in the treatment of loss of sexual interest in surgically menopausal women". Menopause 12 (4): 374-84. PMID 16037752.
- British National Formulary 2007