OK, here's a cut-n-paste from a previous thread......
What we now know about tamoxifen and bodyfat should scare any women away from using it for fat loss (not including the
increased risk of ovarian cancer)! There are two classes of estrogen receptors. One called alpha and one called beta.
Tamoxifen and it’s hyroxylated metabolites are agonists/anatagonists at the alpha receptors and not the beta. The alpha
receptors are plentiful in breast tissue and this makes tamoxifen very good at reducing the effects of estrogen in breast
cancer and male gyno. Sadly, the alpha receptor is actually beneficial to reducing subcutaneous fat, and blocking it with
tamoxifen is less than beneficial to put it nicely! Aside from that, check out the last of these three studies where they
found a significant increase in body fat for women that were treated with tamoxifen!
Site-specific regulation of oestrogen receptor-alpha and -beta by oestradiol in human adipose tissue.
AIM: To examine the expression of oestrogen receptors alpha and beta (ERalpha and ERbeta) and their regulation by
17beta- oestradiol (E2) in adipocytes from human subcutaneous tissue. METHODS: Subcutaneous tissues were obtained
from 10 women ……………………….in adipocytes treated with estradiol, ERalpha expression significantly decreased relative to
control while ERbeta expression increased………………... The feed-back inhibition of ERalpha expression by estradiol in
subcutaneous adipocytes observed in vitro is consistent with the data from ERalpha knock out mice WHERE
SUBCUTANEOUS FAT IS INCREASED. Selective ER modulators may have different effects in different adipose sites.
Demonstration of estrogen receptor subtypes alpha and beta in human adipose tissue: influences of adipose cell
differentiation and fat depot localization.
A novel ER-subtype, the ER-beta has recently been characterized in various tissues, ………………….. ER-alpha and beta were
studied in human adipose tissue. The expression of ER-alpha mRNA was equal in subcutaneous gluteal adipose tissue,
subcutaneous abdominal and intra-abdominal adipose tissue, similar findings were obtained at the protein level.
……………….. the existence of ER-beta isoforms in human adipose tissue was demonstrated and THE AMOUNT OF THESE
RECEPTORS WAS DEPENDENT UPON FAT DEPOT LOCALIZATION, WITH MUCH REDUCED EXPRESSION OF ER-BETA IN
INTRA-ABDOMINAL ADIPOSE TISSUE COMPARED TO SUBCUTANEOUS ADIPOSE TISSUE. These findings may indicate that
estrogens and SERMs could have differentiation and depot specific effects in human adipose tissue.
Body composition measurements using DXA and other techniques in tamoxifen-treated patients.
Tamoxifen is an anti-oestrogenic drug which is widely used in the treatment of patients with breast cancer. There is
increasing interest in using the drug both for benign breast disease and as a chemo-preventative agent of the drug in
women at high risk of breast cancer. Despite the fact that the acute side-effects of the drug are few, its agonistic and
antagonistic oestrogenic effects are not fully known and may have some undesirable effects for patients treated with the
drug for several years. A number of studies carried out recently indicate a varying degree of change in bone mineral
content following treatment with tamoxifen. These studies concentrated mainly on bone mineral density measurements
only and non of them reported the effects of tamoxifen on lean body mass and fat mass. In this study we measured lean
body mass and fat mass in tamoxifen-treated females and a comparison group to determine the difference between the
two groups. Twenty-six women receiving tamoxifen (20 mg/d) have participated in this study. The control group
comprised 31 healthy women of a similar age. Total body bone mineral was measured using a dual-energy X-ray
absorptiometry (DXA). Similarly, regional and total body soft tissue (lean and fat tissue) were measured using the DXA
system. In addition to DXA measurements, percentage body fat (%BF) was measured using total body potassium
counting, skinfold anthropometry, infrared interactance and bioelectric impedance analysis. …………………. there was a
significant difference between the two groups (P < 0.05) for %BF measurement. Similarly there was a significant
difference between the two groups (P < 0.05) for %BF measured by other body composition techniques. Although there is
no other research reported on the effects of tamoxifen on %BF, this retrospective study indicates that tamoxifen may
lead to increase in fat content in women who are subjected to this treatment. WE CONCLUDE THAT THIS OBSERVATION IS
PROBABLY RELATED TO THE AGONISTIC OESTROGENIC EFFECT OF TAMOXIFEN ON BODY FAT. To our knowledge this
deleterious effect has not been reported before and it should be taken into considerable when comprising different types
of anti-oestrogenic drugs. Furthermore, patients should be warned about this side-effect when they are prescribed
Tamoxifen therapy.