I see that priapis posted several studies attempting to support his claim that tamoxifen (nolva) upregulates the progesterone receptor (PgR) in breast tissue. The first
two studies he posted looked at cancerous breast tumors (i.e. not normal breast tissue). The next two studies he posted (
here and
here) looked at the effect in endometrial tissue (the uterus).
First, let's address the latter, endometrial tissue: I've talked about that
here. The gist is that it's no surprise tamoxifen upregulates the PgR in the uterus, where 1) there is high sensitivity to estrogen and *especially* where 2) tamoxifen is known to act as an estrogen receptor agonist (acting like estrogen, not blocking it). This is not the case in normal breast tissue. I argue that Eric Potratz is an idiot (and he is) for extrapolating from endometrial tissue in women to healthy breast tissue in men, without even mentioning (or being aware of) the differential tissue effects. He's misleading people about the dangers of tamoxifen so he can sell a competing product.
Second, let's address the effects in breast cancer tissue: My position is that the effect on PgR expression is not uniform, though there is often a statistically significant increase. If we look at the full text of the first study that priapi posted, we see in table 2 that 24% the tamoxifen group had down-regulation of the PgR, 26% had no change, and 50% showed up-regulation. In contrast,
this study found what they described as "a modest decline" in PgR levels in all three histologies they tested with tamoxifen treatment, though it failed to achieve statistical significance (p values of .19, .82, and .15).
But most importantly, what do we see in normal, healthy breast tissue? Before I address that, note that
earlier in this thread priapis said that I have "an unsupported/undocumented opinion that contradicts science, based on an incorrect reading of some other guys article." He says that the studies above (in cancer tissue and endometrial tissue) "and many more" show that my opinion is incorrect. He ends his post arguing that "the fact of upregulation in BREAST TISSUE is so well established..."
priapis couldn't be more wrong. He fails to understand that there is a significant difference between cancerous breast tumors and normal breast tissue.
This study looked at ER and PgR expression in
normal breast tissue (i.e. not cancer tissue) in tamoxifen treated women. They found that
tamoxifen "shows no stimulatory activity on either PgR levels, a well known oestrogen regulated protein... or the important parameter of cell proliferation (Figure 2)." "In conclusion, the data presented do not show any adverse effects of tamoxifen on normal breast tissue."
This finding was confirmed in the most extensive study that I've seen looking at the effects of tamoxifen in
normal breast tissue, which was published in 2003. This quote couldn't be any more relevant or explicit. Read it and reread it:Here are images showing the effect of different doses of tamoxifen on the level of estrogen receptors (ER, on the left) and progesterone receptors (PR, on the right) in
normal breast tissue:
These results in normal breast tissue are in perfect accordance with my statement that "There is no evidence showing that tamoxifen upregulates the progesterone receptor in the breast (which is what the worry is all about). It shows it does the opposite." priapis is demonstrating his ignorance when he says that this statement "contradicts science." In fact, it's based on the science (and the most relevant science at that).
I stand by my argument that "Nolvadex will not make progesterone related gyno worse. It will help prevent it." (Unless, of course, your breast tissue is a uterus or a cancer
)
-Conciliator
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Originally Posted by Big
