What Are "Designer Estrogens"?

October 7, 2011
Judith A. Norris, RNP

Designer estrogens, SERMS, are two terms currently being used to describe the actions of a medication that acts as an estrogen on one tissue and an anti-estrogen on others. The ideal estrogen medication would switch of or off the effects of estrogen at different sites in the woman's body.

Designer estrogens, SERMS, are two terms currently being used to describe the actions of a medication that acts as an estrogen on one tissue and an anti-estrogen on others. The ideal estrogen medication would switch of or off the effects of estrogen at different sites in the woman's body.

Tamoxifen and Evista (raloxifene), have some of these properties. Tamoxifen is the first SERM used by mainly breast cancer patients and has been shown to block the return of breast cancer in the other breast by 40 percent. The risk associated with Tamoxifen is that it may increase risk of developing blood clots and uterine cancer. Tamoxifen in postmenopausal women acts as an estrogen on bones and increases bone density, increases bone mass 1-3% per year. Neither Tamoxifen or Evista are as effective as Estrogen Replacement Therapy for increasing bone mass, or relieving hot flashes.

Evista (raloxifene), is the latest medication used in osteoporosis prevention. Unlike Tamoxifen, Evista is almost exclusively anti-estrogen in the uterus, it does not increase cell build up in the uterus. Evista has been shown to prevent bone loss and its effect on whether it will help prevent heart disease is being studied. Below see chart on comparison of Premarin and Evista (Raloxifene).

 BreastUterine liningBoneRaises HDL
EstrogenStimulates breast tissuesIncreases uterine liningIncrease bone massIncrease HDL Decreases LDL
TamoxifenBlocks effects of estrogen on breast tissuesIncreases uterine liningIncrease bone massDecrease LDL
RaloxifeneBlocks effects of estrogen on breast tissuesNo effect on uterine liningIncreases bone massDecrease LDL
PhytoestrogensBlocks effects of estrogen on breast tissuesUncertainIncreases bone massUncertain



 Standard dose Hormone replacement. PremarinEvista (Raloxifene)
Benefits  
5-15% HDL (healthy cholesterol)Cardiovascular disease not studied.
OsteoporosisProven
5%-8% BMD spine/hipFracture risk benefit unknown.
hot flashes, night sweats, vaginal drying and painful intercourse, mood swings and skin wrinkles&toneNo effect (may increase hot flashes)
Alzheimer's DiseaseStudies indicate positive affects on memoryNot studied
Risks  
Breast CancerIn some studies with 8-10 yrs of standard dose estrogen , relative risk of 1.25No increase risk in studies up to 3 yrs.
Breast TendernessRare, usually limited to first few months of therapyNone
Vaginal BleedingCyclic regime declining menses Daily regime beyond 9-10 months of therapy there should be no bleedingNo menses

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OBGYN.net © 1999 Judith A. Norris, Ob-Gyn, RNP, OBGYN.net Editorial Advisor