On June 7th Jean Cotterman wrote, in part, "I do not remember associating
that [adoring] feeling with the let-down reflex...  I have trouble with the
new research that states, or at least implies this is 100% due to the
effect of oxytocin. I remember reading a '50's Life magazine reprint from
LLL that described a policeman with a pituitary tumor who felt very
nurturing till it was removed, and of laboratory animals where the males
would make nests and
cuddle the young after being given prolactin shots. In light of that
information, I decided that the surge of prolactin stimulated by each
breastfeeding session must have been responsible for that feeling flooding
over me each time."

K Dettwyler (same date) replied "And it *is* clearly oxytocin that is
responsible for that wonderful affectionate, loving feeling you have when
you breastfeed.  Read the work of Niles Newton.  Prolactin levels return to
their pre-pregnant/non-lactating
levels within six months of birth, and are not associated with continued
milk production, continued amenorrhea, or feelings of affiliation the way
oxytocin is."

(a) There is research supporting the position that prolactin causes "warm
fuzzy" feelings.  Riordan and Auerbach p100: "Prolactin reportedly has a
relaxing effect, causing the breastfeeding woman to feel calm, even
euphoric, during the feeding."  Marie Davis, p90 in the _Core Curriculum
for Lactation Consultant Practice_ (ed. Marsha Walker) cites this statement
and also research by Lauwers and Shinskie 2000 to the effect that prolactin
gives the mother "a feeling of yearning for her baby".

(b) Baseline prolactin levels drop over several months, but not all the way
to pre-pregnancy levels.  Lawrence (5th ed.) p70: "Although it was
initially reported that the high levels of prolactin measured in the first
days and weeks of lactation dwindled to normal baseline by 6 months and
showed no response to suckling stimulus, later studies clearly showed a
different picture with more sensitive assays.  Baseline does not drop to
normal..."  A graph on p 68 shows baseline levels for menstruating
non-lactating women ranging from 8 to 14 ng/ml while the *baseline* levels
for lactating women in the second half-year (i.e. after dropping from the
very high levels of the early postpartum months) are from double to
quadruple those levels, ranging from 30 to 40 ng/ml.  Riordan & Auerbach
p99 cite research saying levels of prolactin remain elevated above
pre-pregnancy baseline levels "for as long as the mother breastfeeds, even
if she breastfeeds for years".

(c) There continues to be a crucial (though highly variable) differential
between baseline levels and a suckling-induced surge in prolactin.  Graphs
on p69 of Lawrence clearly show prolactin surges in response to suckling
which continue to (and past) 180 days.  Lawrence p70 again: "further
stimulus causes a doubling of levels over baseline at all stages of
lactation through the second year."

(d) This prolactin surge does appear to be associated with milk production:
Hale, in recent discussions of pseudoephedrine's effects on lactation,
reports that the drug has the dual effect of flattening the prolactin surge
and approximately halving milk output.  "The surge in prolactin over
baseline levels is critical to milk production" (Lawrence p69).

(e) Prolactin is associated with amenorrhea.  On p100 Riordan & Auerbach
say that higher prolactin levels occur in amenorrheic women than in those
who are cycling and add that "[t]he role of prolactin in the delay of
fertility is well known."

Elise
in pre-exam mode :-)

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