Pituitary Adenoma as a Paraneoplastic Syndrome

00:01 Let's talk about some other paraneoplastic syndromes in particular, endocrine abnormalities.

00:06 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.

00:16 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.

00:31 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.

00:57 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.

01:07 So there are a whole variety of hormones.

01:09 Well if you happen to have a pituitary adenoma that's making one of these, oh my goodness.

01:17 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.

01:30 Too much ACTH induces too many glucocorticoids, mineralocorticoid and androgens which can have definitely downstream effects.

01:39 Too much thyroid stimulating hormone going to stimulate the thyroid and then we will have thyrotoxicity potentially with elevated levels of thyroxine.

01:49 You get the picture.

01:51 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.

02:03 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.

02:20 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.

02:35 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.

02:47 On the right hand side is just an example of what a pituitary adenoma might look like.

02:51 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.

03:07 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.

03:26 It can cause hypogonadism via the mechanism of inhibiting or suppressing luteinizing hormone or follicle stimulating hormone.

03:37 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.

03:46 Let's say it's another different kind of pituitary adenoma, making growth hormone, so called somatotrophic pituitary adenoma.

03:54 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.

04:08 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.

04:21 You can have gonadotropic pituitary adenomas that secrete FSH and LH and you can have thyrotrophic TSH secreting pituitary ademonas.

04:29 You can have a whole variety.

04:31 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.

04:47 Important point as well, it can have a mass effect.

04:50 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.

04:59 You won't be able to see lateral visual fields.

05:02 You can also have headaches as this thing expands, and psychiatric disorders.

05:07 And cognitive dysfunction is not all that uncommon with large pituitary adenomas.

05:12 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.