Hormones Involved in Birth and Lactation
Find out about the hormones involved in Birth & Lactation. For each
one, state where it is secreted from and what its effects are.
Describe whether the mechanisms involved are negative or positive
There are several different hormones that influence the female
reproductive system and the two most fundamental hormones are
progesterone and oestrogen. Progesterone is a steroid hormone and has
a number of physiological effects on the body such as normalising
blood clotting and vascular tone, zinc and copper levels, cell oxygen
levels, and the use of fat stores for energy and it also assists in
the thyroid function. It is usually required to normalise or restore
changes caused by oestrogen. It affects all aspects of pregnancy,
prepares breasts for lactation and the relaxation of joints and
ligaments in preparation of childbirth. It can affect bowel movements
usually causing constipation and back pain and raises the body
Oestrogens are a group of steroid compounds that function as the
primary female sex hormone. Developing follicles in the ovaries, the
corpus luteum and the placenta primarily produces them and some
secondary sources in smaller amounts can be found in the liver,
adrenal glands and breasts. Although oestrogen is present in both male
and females, it is found to be significantly higher in women and is
involved in controlling the menstrual cycle. As does progesterone,
oestrogen also affects all aspects of the pregnancy and is
particularly important in maintaining the health of the genital track,
the reproductive organs and the breasts.
Throughout pregnancy gradually the levels of progesterone in the blood
fall and the levels of oestrogen rise. It is this process that brings
about parturition as the oestrogen helps the uterine to contract &
progesterone inhibits it. It is thought that miscarriage or premature
births can be a result of insufficient levels of progesterone.
As in most biological control systems the release and control
mechanism for managing these hormones is known as negative feedback.
The feedback loop causes the detector (pituitary gland) to either
inhibit or stimulate the production of oestrogen or progesterone when
required and keep the levels from deviating from the ‘norm’.
However, there is a more direct form of labour, which is caused from
the release of the hormone oxytocin, a nine amino acid peptide
hormone, synthesised in the neurosecretory cells in the hypothalamus
which instructs the posterior lobe of the pituitary gland to secrete.
The oestrogen encourages the uterine muscle to be more sensitive to
oxytocin and therefore...