Very interesting thoughts from Barbara and Sara. I'd like to throw two
more levels into this-- up and down regulation of receptors, and
interferences. That makes 4 possible problems:

1) enough good receptors but not enough hormone
2) enough hormone and enough receptors, but receptors resistant to
prolactin
3) enough hormone but not enough receptors-either poor
proliferation/regulation, or simply not enough target breast tissue
4) interference of another hormone-- could affect production of
prolactin or development of receptors

Barbara's idea of "distracting" prolactin from the breast tissue could
play into #2.

Another thought: it is my understanding that oxytocin and prolactin both
up-regulate their own receptors. This means that the more exposure of
the breast tissue to these hormones, the more receptors will in turn
proliferate-- at least in the short run. This implies a negative spiral
when the levels are low.

Regarding Sara's thoughts on stress: Cortisol, which is important for
milk production, increases when stress occurs (great article--
http://stress.about.com/library/weekly/aa012901a.htm). Yet, too much
cortisol inhibits lactation. "In contrast with casein or WAP genes,
cortisol, in the presence of insulin and prolactin, has a dose-dependent
action on alpha-lactalbumin; it activates the gene expression at low
concentration (30nM) but inhibits it at concentrations above 300nM
(34-36)." (from Biology of the Mammary Gland:
http://mammary.nih.gove/reviews/gene_expression/Vilotte001/index/html)

>>Here's another idea, which might be way of ball, but anyway. NIDDM
patients have insulin resistance. Once way of helping decrease insulin
resistance in tissues (i.e. muscle) is to exercise and train them, this
also has to do with insulin receptors. Could this work in the breasts -
does training the breast (i.e. pumping in Barbara's post) decrease
prolactin resistance - if it exists of course - by making the lactocytes
more likely to bind prolactin?<<

I know that weight loss, whether from exercise or diet, reduces insulin
resistance; I am not familiar with the concept of exercising of muscles
(conditioning?) being a factor also, so I cannot speak to that thought.
However, perhaps the idea of "training" the breast could be related to
the idea of frequency of feeds or exposure of breast to prolactin, which
theoretically upregulate prolactin receptors, resulting in greater
response from the breast.

Stimulating discussion!

~Lisa Marasco

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