PUBERTY AND BREAST DEVELOPEMENT

Puberty
At puberty, the increase in breast size is mainly caused
by the increased deposition of adipose tissue within the
gland. However, progressive elongation and branching of
the ducts creates a more extensive ductal network.
10
The
major site of growth is the bud-like structures at the end
of the ducts, and these form the terminal duct lobular
units or acini.
11
Although knowledge of the hormonal
regulation of mammary growth during puberty is not
extensive, these maturational changes are associated with
increased plasma concentrations of oestrogen, prolactin,
luteinizing hormone, follicle stimulating hormone, and
growth hormone.
12,13
Menstrual Cycle Changes
During the follicular phase of the menstrual cycle, the
lobules are small, with few alveoli, and there is low
mitotic activity. During the luteal phase, the lobules and
alveoli develop with open lumens and mitotic activity is
at its greatest.
14
From day 27 to menstruation, these
changes regress. However, the degeneration of the epi-
thelial growth is not complete,
15
and some of the follic-
ular growth remains until the next cycle. With increasing
years, there is a relative decrease in mitotic activity until
about 35 years of age, when breast development plateaus