Let's revise some of the physiology and anatomy
of the hypothalamic pituitary axis.
The anterior pituitary gland secretes
a number of different hormones.
Let's revise some of these
before we get into the cases.
Adrenocorticotropic hormone is activated by CRH
or corticotropin-releasing hormone
which is secreted from
Thyroid-stimulating hormone likewise
is activated in the anterior pituitary
by thyroid-releasing hormone
from the hypothalamus.
Prolactin, generally responsible
for activation of lactation,
is inhibited by hypothalamic
secretes two hormones from the anterior pituitary.
These are luteinizing hormone
and follicle-stimulating hormone,
which are important in the
control of reproduction.
And then finally, growth hormone is inhibited
in response to somatostatin.
Moving on to the posterior pituitary gland,
it's a little less complicated,
there are only two hormones here
to be aware of.
Firstly, oxytocin, which is necessary
and is secreted in and
And then finally, antidiuretic hormone
also called vasopressin,
which regulates water balance.
Let's go through these in the
schema that shows you
exactly how the hypothalamic hormones activate
the anterior pituitary hormones
to then go on and perform
their metabolic functions.
Starting with corticotropin-releasing hormone,
ACTH is released,
and then acts on the adrenal cortex
to produce cortisol,
which has important functions
in many metabolic actions.
Likewise, thyroid-releasing hormone
from the hypothalamus
causes thyroid-stimulating hormone release
from the anterior pituitary,
which then acts on
the thyroid gland.
The thyroid gland is actually the largest
independent endocrine organ.
This will resecrete thyroid hormones,
which also have a major role in metabolism.
Thyroid-releasing hormone will also
activate prolactin, interestingly.
Prolactin has an effect on the breast
and is mainly concerned with lactation.
And then finally, dopamine
from the hypothalamus
has a negative action
on prolactin release.
Gonadotropin-releasing hormone will activate
FSH and LH in the anterior pituitary.
These two hormones have actions
on the gonads.
In the male, mainly androgen production,
and in the female, estrogen production.
Somatostatin actually inhibits
growth hormone release.
But growth hormone
secreted from the anterior pituitary
will have endocrine targets
particularly in the liver
where insulin-derived growth factor
and then it will have nonendocrine targets
in many tissues around the body.
Moving on to the posterior pituitary,
the only two significant hormones
to be aware of secreted from the posterior
pituitary gland are oxytocin
which acts on uterine muscles
and the mammary glands,
and ADH which has an important role
in renal tubular reabsorption of sodium.
ADH is antidiuretic hormone.
As we'll discuss in the cases,
this has important effects
on sodium metabolism
and water balance.