I have seen two abstracts recently which I thought were of interest.

 The first I cannot find at the moment and I haven't looked at the article
yet to see how good a study it was.  But as I recall the abstract said the
study found that mothers who were anemic showed a tendency to feel that they
had not enough milk by the time the baby was six months of age and weaned
sooner than non-anemic mothers.  I'll  try to find it.

The second is entiltled Growth Hormone Increase Breast Milk Volumes in
Mothers of Preterm Infants by Alistair J Gunn et al..  The results indicated
that all women treated with recombinant human growth hormone showed a modest
increase of milk production [from 139+or - 49 mL/day to 174 = or - 46 mL/day]
after 7 days of treatment, a rise of 31% compared to the placebo group which
showed a 7% increase, which was not significant, and had some mothers whose
production actually decreased.  It's in Pediatrics v. 98 no. 2 August 1996.
p. 279.  They stated that growth hormone has been reported to be important
 in galactopoieses in several species. The mothers had no increases in grwoth
hormone in their plasma but did show rises in insulinlike growth factor [IGF]
and  an IGF binding protein.