Pituitary Flashcards
What is the relationship between dopamine and prolactin?
Dopamine inhibits prolactin synthesis and release from the anterior pituitary
What hormone release from the hypothalamus decreases the release of growth hormone from the anterior pituitary?
Somatostatin
List the three cell types found in the adenohypophysis (anterior pituitary)
Acidophils - stains red
Basophils- stains blue
Chromophobes- stains clear
All three grow together, and clusters are separated by a reticulin network
List the cell types present in the neurohypophysis
The neurohypophysis resembles neural tissue- it has glial cells, nerve fibers, nerve endings, and intra-axonal neurosecretory granules
What is the most common cause of hyperpituitarism?
Functional anterior pituitary adenoma
Functional indicates they are actively secreting hormone
Differentiate micro vs macroadenomas
microadenoma: <1cm
macroadenoma: >1cm
Which is the most common kind of pituitary adenoma?
Lactrotrophs- secretes Prolactin
What is the second and third most common hormones secreted from pituitary adenomas?
2- GH
3- ACTH
What are the classic mass effect symptoms caused by pituitary adenomas?
Bitemporal hemianopsia (with macroadenoma)
…also headaches
Do functional or non-function adenomas tend to be larger upon presentation?
Non-functional, because the only symptoms are caused by mass-effect
MEN 1 includes neoplasms of what three structures?
parathyroid, pancreas, and pituitary
Are pituitary adenomas familial or sporadic?
95% sporadic
5% familial
What is the role of GNAS1 in many pituitary adenomas?
GNAS1 gene mutations –> constitutive activation of Gs protein –> unchecked cellular proliferation (ultimately through cAMP)
How do females present with a prolactinoma?
Galactorrhea
Infertility and amenorrhea (prolactin inhibits LH surge)
Women present earlier because they realize they’re no longer menstruating regularly
How do males present with a prolactinoma?
Infertility and impotence
Name two drugs that are used to treat prolactinomas
Dopamine agonists: bromocriptine and cabergoline
How are macroadenomas of the pituitary treated?
Surgical resection
What cell type is responsible for the production of growth hormone?
Somatotrophs
Persistent GH stimulation in the liver leads to over-production of what?
Insulin-like growth factor 1 (IGF-1)
Contrast the effects of a GH producing pituitary adenoma in prepubertal vs post-puberty patients
Pre-puberty –> gigantism
Post-puberty–> acromegaly
List three ways we diagnose GH adenoas
Increased IGF-1 serum levels
Increased GH serum levels
Lack of GH suppression by oral glucose
List two treatments for GH adenomas
1) surgical resection
2) Somatostatin analogs
Name two specific somatostatin analogs
Octreotide
Lantreotide
Corticotrophs produce which hormone?
ACTH
What is cushings disease?
Hypercortisolism via pituitary adenoma
Along with symptoms of hypercortisolism, what other unique skin finding is seen with excess ACTH production?
Hyperpigmentation
POMC –> ACTH and melanocyte stimulating hormone
What is Nelson syndrome?
Removal of adrenal gland in presence of corticotroph adenoma –> rapidly progressing mass (no more feedback from adrenal glands
–> Mass effect and hyperpigmentation, but no excess cortisol
List 4 potential causes of hypopituitarism
1) Nonfunctional pituitary adenoma
2) Ischemic injury
3) Surgery, radiation
4) Inflammatory conditions
What is a pituitary apoplexy?
Acute hemorrhage into an adenoma
-If ACTH is eliminated –> lack of cortisol and hypotensive emergency
What causes Sheehan syndrome?
Post partum necrosis of the anterior pituitary (posterior pituitary has some collateral circulation)
The anterior pituitary is particularly sensitive to ischemic damage, and so is vulnerable following a postpartum hypotensive state
What is the initial clinical clue as to Sheehan syndrome?
Lack of lactation (due to lack of prolactin)
Is Sheehan syndrome dangerous?
Yes- there can be a life-threatening lack of secondary adrenal insufficiency
What can cause primary empty sella syndrome?
Increased CSF pressure causes pituitary atrophy
ADH deficiency leads to __________
Central diabetes insipidus
Excess ADH secretion is called ________–
SIADH
What is desmopressin?
Synthetic ADH analog
How does central diabetes insipidus respond to desmopressin?
It does respond
What is nephrogenic diabetes insipidus?
Renal tubules are unresponsive to ADH - does not respond to desmopressin
Do patients with central diabetes insipidus have hypo or hypernatremia?
HYPERnatremia (they are dehydrated due to free water loss)
Do people with SIADH have hypo or hypernatremia?
They usually have euvolemic hyponatremia
They dilute out their Na+, but generally are not fluid overloaded
Total body water increases, blood volume remains nearly normal (clinically euvolemic)
What is the most common paraneoplastic cause of SIADH?
Small cell carcinoma of the lung
List a few drugs that can cause SIADH
SSRIs, carbamazepine, chlorpromazine, cyclophosphamide
What does Rathke’s pouch develop into?
The anterior pituitary
What are the tumors that can arise from Rathke’s pouch?
Craniopharyngioma
Where do craniopharyngiomas occur?
Suprasellar
Are craniopharyngiomas benign or malignant?
THey are benign, but tend to recur after resection
What is a Rathke cleft cyst? Why are they important?
Developmental failure of Rathke’s pouch obliteration
They’re important because their growth may compromise the pituitary gland
