Thankyou Rachael and Katherine for your suggestions.
A bit more digging has revealed that maternal condition does affect
prolactin secretion. The fatter (and I'm not necessarily talking about
obesity here) the less prolactin is released in response to suckling. As
Rachael mentioned this results in longer periods of lactational infertility
in thinnner women (all other factors being equal). I know that older women
also have longer periods of lactational infertility but I don't know if this
is due to higher prolactin levels and have not been able to find anything on
this so far (help anyone?). I have tacked on some abstracts below. The
reason why I am interested in this is that I am delving further into why
women in developing countries are better at relactation/induced lactation
than those in the West. The possibility arises that thinner women may have
higher prolactin levels which would really help for relactation/induced
lactation and since there is an epidemic of over eating in the West been
"fatter" may be a disadvantage that women more commonly experience in the
West, though I don't believe that it would be a major factor. Any comments?
Karleen Gribble
Australia

Lunn PG.  Austin S.  Prentice AM.  Whitehead RG.
Title
  The effect of improved nutrition on plasma prolactin concentrations and
postpartum infertility in lactating Gambian women.
Source
  American Journal of Clinical Nutrition.  39(2):227-35, 1984 Feb.
Abstract
  A substantial increase in food consumption of lactating Gambian women has
been shown to be associated with a reduction in their plasma prolactin
concentration. Women receiving food supplements during pregnancy as well as
in lactation exhibited an even greater lowering of the postpartum plasma
levels of this hormone. Consequently prolactin values of supplemented women
returned more quickly to levels which allowed the resumption of menstrual
and ovulatory activity. Concurrent measurements of the plasma concentrations
of estradiol and progesterone in addition to prolactin allowed the
calculation of prolactin values at which half the lactating women could be
expected to have resumed menstruation and ovulation. These values were 1007
and 759 microU/ml, respectively. Dietary improvement during lactation alone
resulted in these critical prolactin concentrations being reached 21 wk
earlier than in nonsupplemented counterparts, while those receiving the
extra food in both pregnancy a!
nd lactation showed a 35-wk shortening of postpartum amenorrhea and
infertility.
Other Abstract
  A substantial increase in food consumption of lactating Gambian women has
been shown to be associated with a reduction in their plasma prolactin
concentration.  Women receiving food supplements during pregnancy as well as
in lactation exhibited an even greater lowering of the postpartum plasma
levels of this hormone.  Consequently prolactin values of supplemented women
returned more quickly to levels which allowed the resumption of menstrual
and ovulatory activity.  Concurrent measurements of the plasma
concentrations of estradiol and progesterone in addition to prolactin
allowed the calculation of prolactin values at which 1/2 the lactating women
could be expected to have resumed menstruation and ovulation.  These values
were 1007 and 759 U/ml, respectively.  Dietary improvement during lactation
alone resulted in these critical prolactin concentrations being reached 21
weeks earlier than in nonsupplemented counterparts, while those receiving
the extra food in both pregnancy!
 and lactation showed a 35-week shortening of postpartum amenorrhea and
infertility..author's modified

Authors
  Lunn PG.  Prentice AM.  Austin S.  Whitehead RG.
Title
  Influence of maternal diet on plasma-prolactin levels during lactation.
Source
  Lancet.  1(8169):623-5, 1980 Mar 22.
Abstract
  An improvement in maternal diet produced significant reductions in
plasma-prolactin concentration at all stages of lactation. The prolonged
high prolactin concentrations found in undernourished mothers may ensure
milk synthesis when food intake is limited, by preferentially channelling
nutrients towards the breast. The lower hormonal levels associated with
improved maternal nutrition may shorten the period of post-partum
infertility despite prolonged breast-feeding.
Other Abstract
  Blood samples collected from 30 lactating mothers from Cambridge, England
and 119 lactating mothers from Gambia were analyzed to determine whether
plasma-prolactin concentration during lactation responded to changes in the
maternal diet.  Plasma-prolactin level was measured by a double antibody
radioimmunoassay technique.  Breast milk output was measured in both
countries by a test-weighing procedure and some values were confirmed by the
deuterium-oxide dilution method.  Gambian mothers were found to have a much
higher concentration of plasma-prolactin for longer periods than their
British counterparts.  Seasonal changes in Gambia were also associated with
substantial differences in maternal nutrition.  During the wet season food
intake in generally low and there is much heavy manual labor.  The findings
strongly suggest that maternal dietary intake has a major effect on
plasma-prolactin.  The better the nutritional status, the lower the
prolactin levels throughout lactation!
 and the sooner the return to normal status.  Improved nutritional status
may reduce the period of postpartum infertility despite prolonged
breastfeeding.  The known effect of frequency of breastfeeding on plasma
prolactin has not been fully evaluated but some of the differences between
the 2 countries could be due to the fact that Gambian mothers feed their
children 10-16 times a day compared with an average of 6 times a day in
England.  Nutritional programs aimed at lactating mothers and their infants
should reconsider the need for some artificial contraceptive method.



Authors
  Kopelman PG.
Institution
  St Bartholomew's and the Royal School of Medicine and Dentistry, Queen
Mary and Westfield College, University of London, UK.
[log in to unmask]
Title
  Physiopathology of prolactin secretion in obesity. [Review] [31 refs]
Source
  International Journal of Obesity & Related Metabolic Disorders: Journal of
the International Association for the Study of Obesity.  24 Suppl 2:S104-8,
2000 Jun.
Abstract
  In many species prolactin is of biological importance and has a major role
in determining the deposition and mobilization of fat. In human physiology,
outside pregnancy, prolactin secretion is altered by increasing body weight
in both children and adults. Prolactin in this circumstance appears to be
marker of hypothalamic-pituitary function: the prolactin response to
insulin-hypoglycaemia, thyrotrophin releasing hormone stimulation and other
stimulatory factors may be diminished. In addition, obesity alters the 24h
spontaneous release of prolactin with a generalised dampening of release. A
number of explanations have been given as possible causes for these
alterations, but it seems likely that they reflect obesity per se and are
associated with hyperinsulinaemia. Weight reduction, with accompanying
decrease in plasma insulin levels, leads to a normalization of prolactin
responses in most, but not all, circumstances. To date, no molecular basis
has been identified which links!
 prolactin with increasing body fatness, weight and appetite: new data
suggests a possible link in obese men between fasting plasma prolactin and
leptin concentrations. [References: 31]

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