Definition of HRT

Hormone Replacement Therapy (HRT) is medication containing one or more female hormones, commonly estrogen plus progestin (synthetic progesterone). Some women receive estrogen-only therapy (usually women who have had their uterus removed). HRT is most often used to treat symptoms of menopause such as "hot flashes", vaginal dryness, mood swings, sleep disorders, and decreased sexual desire. This medication may be taken in the form of a pill, a patch, or vaginal cream.

Background

Based on early studies, many physicians believed that HRT might be beneficial for reducing the risk of heart disease and bone fractures caused by osteoporosis (thinning of the bones) in addition to treating menopausal symptoms. However, after the July 2002 release of "Risks and Benefits of Estrogen plus Progestin in Healthy Postmenopausal Women" by the Writing Group for the Women's Health Initiative (WHI) ( WHI Web Site: http://www.whi.org Investigators, the use of Hormone Replacement Therapy (HRT) could be expected to decline. The results of this 5 year study showed healthy postmenopausal women taking estrogen plus progestin versus placebo were at greater risk for Congestive Heart Disease, Breast Cancer, Stroke and Pulmonary Embolism. These results have led physicians to revise their recommendations regarding HRT.

Incidence and Prevalence

The incidence of HRT is the proportion of women starting HRT use for the first time (that is, women receiving a prescription for HRT, having not received any HRT drugs in the previous fiscal year). Prevalence is the proportion of women using HRT medication.

In Fransoo et al. (2005) the prevalence was defined by the number of Manitoba female residents using HRT drugs in the fiscal year, divided by the number of Manitoba female residents in the province as of Dec. 31 of that year. A woman must have at least one prescription for a HRT drug in the fiscal year to be counted as a prevalent case for that year.

The incidence was defined by the number of Manitoba female residents starting HRT drugs in the fiscal year, divided by the number of Manitoba female residents in the province as of Dec. 31 of that year. A woman cannot have any prescriptions in the year prior to her first prescription of HRT in the study year to be counted as an incident case for that year.

Drug Program Information Network (DPIN) data was used to define this indicator.

HRT Drugs

HRT drugs included in Fransoo et al. (2005) use the Anatomical Therapeutic Chemical (ATC) Drug Classification System which was developed by the World Health Organization's Collaborating Centre for Drug Statistics Methodology: http://www.whocc.no/ . This list was carefully developed and validated by Patricia Caetano for her dissertation research:


1. Natural and Semi-synthetic Estrogens
   1. Ethinylestradiol (ATC Code G03CA01)
      
   2. Estradiol (ATC Code G03CA03)
      
   3. Estrone (ATC Code G03CA07)
      
   4. Conjugated estrogens (ATC Code G03CA57)
   
   
2. Progestogens and Estrogens, fixed combinations
   1. Norethisterone and estrogen (ATC Codes G03AA05, G03FA01)
   
   
3. Progestogens and Estrogens, sequential preparations
   1. Norethisterone and estrogen (ATC Code G03FB05)

Note: This list of drugs should be reviewed by a pharmacist or clinician each time it is used in research, as new formulations are continually being added.