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Both male and female infants may have palpable breast tissue at birth.
This is due to the stimulation of the breast by maternal hormones
during pregnancy.
By two to three months of age the breast tissue regresses.
Madlon-Kay found that 38 of 640 infants had galactorrhea
("witch's milk") secretion at some time during the first
two months of life. The galactorrhea was most likely to be present
in the first two weeks of life (
Madlon-Kay, 1986
).
A woman's breasts grow during puberty in response to hormones.
These hormones include:
prolactin, estrogen, progesterone, cortisol, insulin, thyroid hormones
and growth hormone.
During puberty the release of these hormones causes proliferation of the
lactiferous ducts and the development of breast tissues.
During pregnancy breasts increase in size due to an increase in lobules
and alveoli.
The release of estrogen and progesterone from the placenta and prolactin
from the adenohypophysis causes the breast development.
Women's breasts are prepared to produce milk as early as the sixteenth
to the twentieth week of gestation.
Breast milk production is inhibited during pregnancy by the effect of
progesterone on prolactin.
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