Let's talk about some other
paraneoplastic syndromes in particular,
And in this particular case, we're
going to talk about pituitary adenomas,
which is a benign tumor, and yet can
have profound systemic manifestations.
So this is just a schematic and maybe at some
point we will talk about endocrine tissues
but for here I just want you to see that
there is the anterior pituitary gland
that is getting signals from the hypothalamus.
That anterior pituitary gland can
make a whole variety of hormones
that are going to activate a variety of systems
around the body, including growth hormone,
adrenocorticotrophic hormone that
will stimulate the adrenal cortex,
thyroid stimulating hormone TSH, that
will stimulate the thyroid gland,
follicle stimulating hormone and luteinizing hormone
that are very important for ovarian folliculogenesis.
Luteinizing hormone, it's also important
for having the normal development
and testosterone production by the testes,
and prolactin which will be
very important for lactation.
So there are a whole variety of hormones.
Well if you happen to have a pituitary
adenoma that's making one of these,
oh my goodness.
Too much growth hormone means that
we will have insulin growth factors
that can cause increased growth,
and we will talk about some of those
manifestations such as acromegaly.
Too much ACTH induces too many glucocorticoids,
mineralocorticoid and androgens
which can have definitely downstream effects.
Too much thyroid stimulating hormone
going to stimulate the thyroid
and then we will have thyrotoxicity
potentially with elevated levels of thyroxine.
You get the picture.
So, again, pituitary adenomas are,
for the most part completely benign
but can have a lot of manifestations, including
the endocrine ones that we just discussed.
What you're seeing here on the left
hand side with a green circle rounded
is a rather large pituitary adenoma that's
compressing the optic chasm beneath it,
and that is also putting out a
variety of pituitary hormones.
Usually it's one cell type that has expanded
so you don't usually have a pituitary adenoma
that's putting out ACTH and thyroid stimulating
hormone, it's usually just one of that whole list
because only one cell is expanding.
And notably, most pituitary adenomas are
non-secreting, they don't make any hormone
but the ones that do may have interesting
effects, as we've talked about.
On the right hand side is just an example
of what a pituitary adenoma might look like.
It's a rather banal collection of mononuclear
cells that have an open chromatin pattern,
sometimes in very prominent nucleolus
and kind of a granular cytoplasm
and it's usually a kind of a monomorphic population.
Well, so what happens with these benign
pituitary adenomas that are secretory,
the ones that are making various hormones?
Well, if it's a lactotrophic hormone of
pituitary adenoma, it will make prolactin
which will cause galactorrhea, breast milk
so you will have actual milk production.
It can cause hypogonadism via the mechanism of
inhibiting or suppressing luteinizing hormone
or follicle stimulating hormone.
You can have amenorrhea again
through the same general pathway,
you can have infertility you can have
impotence, as a result of too much prolactin.
Let's say it's another different kind of
pituitary adenoma, making growth hormone,
so called somatotrophic pituitary adenoma.
In that case, we're going to get
acromegaly, we're going to get
frontal bossing on the forehead,
enlarged hands, etc., we get gigantism
because this is driving the growth
of bone as well as other tissues.
We can have a corticotrophic pituitary
adenomas that's secreting too much ACTH
and we'll get Cushing's disease so
we will have elevated glucocorticoids
and we'll have all the Cushingoid
manifestations of that.
You can have gonadotropic pituitary
adenomas that secrete FSH and LH
and you can have thyrotrophic
TSH secreting pituitary ademonas.
You can have a whole variety.
Again, just to reiterate, most
pituitary adenomas are non-secretory
and but when they are secretory, it's usually
just one of the hormones that are potentially
synthesized within pituitary cells.
Important point as well, it can have a mass effect.
Clearly this large thing that we're
looking at with a green circle around it
is pressing on the optic chasm so you
will tend to have bitemporal hemianopsia.
You won't be able to see lateral visual fields.
You can also have headaches as this
thing expands, and psychiatric disorders.
And cognitive dysfunction is not all that
uncommon with large pituitary adenomas.
Small ones can be very potently secretory and
may not have any of these other mass effects,
but something of this size
probably has a mass effect,
disproportionate to the amount
of endocrine abnormalities.