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Endocrine > Pituitary Gland B&B > Flashcards

Pituitary Gland B&B Flashcards

1
Q

where is the pituitary gland found within the brain?

A

sits in a small cavity of the sphenoid bone called the sella turcica

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2
Q

what does it mean that the pituitary gland is a circumventricular organ (CVO)?

A

does not contain blood brain barrier – connects to the medium eminence of the hypothalamus via the pituitary stalk

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3
Q

from what embryonic tissue is the posterior pituitary gland derived?

A

A.k.a. neurohypophysis – derived from neural ectoderm in the floor of the forebrain

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4
Q

from what is the anterior pituitary gland derived?

A

aka adenohypophysis - derived from Rathke’s pouch, outgrowth of oral cavity

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5
Q

What are the five cell types of the anterior pituitary gland?

A
  1. corticotrophs —> ACTH
  2. thyrotrophs —> TSH
  3. gonadotrophs —> LH, FSH
  4. somatotrophs —> GH (aka somatotrophin)
  5. lactotrophs —> prolactin
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6
Q

Which two inhibitory hormones are secreted from the hypothalamus and act on the anterior pituitary via the hypothalamic portal system?

A
  1. dopamine - inhibits prolactin
  2. somatostatin - inhibits GH (aka somatotropin) and TSH

all others are stimulatory (CRH, TRH, GnRH, GHRH)

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7
Q

describe the mechanism by which dopamine inhibits prolactin release from the anterior pituitary

A

hypothalamus releases dopamine, which binds inhibitory D2 receptors on lactotrophs —> decreased prolactin secretion

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8
Q

Levels of which hormone from the anterior pituitary will increase following destruction of the hypothalamus?

A

prolactin – under inhibitory control from the hypothalamus via dopamine (binds inhibitory D2 receptors on lactotrophs)

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9
Q

Explain why hypothyroidism is in the differential for pituitary enlargement in hyperprolactinemia

A

TRH (thyrotropin-releasing hormone) induces prolactin release

in hypothyroidism, the body responds by increasing TRH —> predisposes to hyperprolactinemia

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10
Q

Which hormone is responsible for the growth in pituitary size seen during pregnancy?

A

estrogen stimulates gene transcription and prolactin release within lactotrophs during pregnancy —> pituitary can grow in size

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11
Q

what is the effect of prolactin on gonadotropin releasing hormone (GnRH)?

A

GnRH (hypothalamus) stimulates FSH and LH secretion from anterior pituitary

prolactin (which rises during pregnancy) inhibits GnRH —> lack of FSH and LH signaling results in cessation of ovulation and menstruation

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12
Q

given that prolactin rises in pregnancy, why does milk production not occur in pregnancy?

A

Estradiol and progesterone block prolactin’s effect on milk – after childbirth, these hormones fall and milk production occurs

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13
Q

what kind of drugs are cabergoline and bromocriptine?

A

dopamine agonists - can treat Parkinson’s and prolactinomas (inhibit release via D2 receptors)

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14
Q

what diseases result from pituitary adenomas originating in the following cell types, and which is most common?
a. lactotrophs
b. thyrotrophs
c. corticotrophs
d. somatotrophs

A

a. lactotrophs —> prolactinoma/ hyperprolactinemia (most common)
b. thyrotrophs —> central hyperthyroidism
c. corticotrophs —> Cushing’s disease (excess cortisol)
d. somatotrophs —> acromegaly / gigantism

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15
Q

what is the classic cause of bitemporal hemianopsia?

A

pituitary adenomas - cause compression of the superior optic chiasm

loss of temporal (outside) vision on both sides - recall the nerves of the optic chiasm cross over

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16
Q

how would a prolactinoma (hyperprolactinemia) present in females vs males?

A

females - amenorrhea (inhibited GnRH —> lack of FSH, LH), galactorrhea, fractures (low estrogen —> low bone density)

males - “hypogonadotropic hypogonadism” —> decreased libido, infertility, gynecomastia

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17
Q

which pituitary adenoma can be treated with cabergoline and bromocriptine?

A

these are dopamine agonists, which can treat prolactinoma

inhibit prolactin release via D2 receptor binding

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18
Q

what would you predict the side effects are of the following drugs: haloperidol, risperidone, metoclopramide

A

haloperidol and risperidone are antipsychotics, metoclopramide is an antiemetic - all are dopamine antagonists; block D2 (dopamine2) receptors

this causes an increase in prolactin —> amenorrhea, breast engorgement, galactorrhea, sexual dysfunction

also cause Parkinsonian symptoms

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19
Q

what kind of drugs are haloperidol, risperidone, and metoclopramide

A

haloperidol and risperidone: antipsychotics
metoclopramide: antiemetic

all are dopamine antagonists; block D2 (dopamine2) receptors

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20
Q

what would be the effects of hemorrhage, ischemia, or a compressing mass to the anterior pituitary?

A

ACTH deficiency —> shock/hypotension (low cortisol)

TSH deficiency —> hypothyroidism

LH/FSH deficiency —> hypogonadism

21
Q

why wouldn’t hemorrhage of the anterior pituitary present with salt wasting?

A

aldosterone is controlled by the RAAS system, therefore, its function is not lost

22
Q

from what is a craniopharyngioma derived?

A

benign tumor in children 10-14yo, derived from remnants of Rathke’s pouch (embryonic source of pituitary gland)

presents with symptoms of compression of pituitary gland: hypopituitarism, headache, visual field defects, also behavioral change via frontal lobe dysfunction

23
Q

benign tumor in children 10-14yo, derived from remnants of Rathke’s pouch

A

craniopharyngioma

presents with symptoms of compression of pituitary gland: hypopituitarism, headache, visual field defects, also behavioral change via frontal lobe dysfunction

24
Q

Pt is an 11yo F presenting with hypopituitarism, headache, bilateral temporal vision loss, and behavioral changes as noted by her parents. What is most likely going on?

A

craniopharyngioma: benign tumor in children 10-14yo, derived from remnants of Rathke’s pouch (embryonic source of pituitary gland)

25
Q

what is empty sella syndrome and who will it most likely present in?

A

enlarged sella turcica (where pituitary gland sits) partially filled with CSF —> compresses pituitary gland, causing hypopituitarism

more common in women with obesity/ HTN

26
Q

what occurs in pituitary apoplexy?

A

sudden hemorrhage into the pituitary gland, usually from pre-existing adenoma

presents with shock/ severe hypotension (loss of cortisol), diplopia (pressure on oculomotor nerves), and sudden onset of severe headache

27
Q

on rounds, a patient receiving treatment for a pituitary adenoma complains of a sudden, severe headache and loss of vision, and is showing signs of shock - what are you concerned about?

A

pituitary apoplexy: sudden hemorrhage into the pituitary gland, usually from pre-existing adenoma

presents with shock (loss of cortisol), diplopia (pressure on oculomotor nerves), and sudden onset of severe headache

28
Q

sheehan syndrome

A

postpartum hemorrhage (ischemic necrosis) of pituitary gland - recall pituitary enlarges in pregnancy, making it vulnerable to infarction from hypovolemic shock

presents as shock (hypotension) after delivery or failure to lactate (due to hypopituitarism)

29
Q

Shortly after giving birth, a women goes into shock. She also had been failing to lactate. What are you worried about?

A

Sheehan syndrome: postpartum hemorrhage of pituitary gland - recall pituitary enlarges in pregnancy, making it vulnerable to infarction from hypovolemic shock

presents as shock (hypotension) after delivery or failure to lactate (due to hypopituitarism)

30
Q

somatotrophin, aka _____, is important for…

A

somatotrophin = growth hormone

protein hormone, important for linear (height) growth in childhood

released in pulsatile manner (undetectable levels in between)

31
Q

name 3 things that stimulate and inhibit release of growth hormone (somatotrophin) from the anterior pituitary

A

stimulate:
1. GHRH (hypothalamus)
2. sleep
3. exercise

inhibit:
1. glucose
2. somatostatin (hypothalamus)
3. IGF-1 (insulin like growth factor 1)

32
Q

what occurs immediately after growth hormone binds its receptor?

A

protein hormone, binds membrane receptor —> activates JAK2 (cytoplasmic tyrosine kinase)

this causes phosphorylation of tyrosine residues within JAK2 itself and GH receptor - forms binding sites for signaling molecules —> altered gene expression

33
Q

what happens when growth hormone binds receptors in the liver?

A

causes secretion of IGF-1 (insulin like growth factor 1, aka somatomedin) - mediates effects of growth hormone

levels of IGF-1 can be measured in serum as indicator of GH function

34
Q

what is the effect of growth hormone on glucose metabolism?

A

decreases glucose uptake (anti-insulin) / raises blood sugar (“diabetogenic”)

peripheral tissues exposed to GH become insulin resistant, inducing hyperinsulinemia

35
Q

what is the effect of growth hormone on fatty acid metabolism?

A

promotes lipolysis via activation of hormone sensitive lipase

36
Q

indirect effects of growth hormone are mediated by IGF-1 and include… (3)

A

IGF-1 = insulin like growth factor

  1. activation of chondrocytes —> increased linear growth
  2. increase lean muscle mass
  3. increase organ size
37
Q

what is the consequence of growth hormone excess in children vs adults?

A

children —> gigantism (linear growth, very tall child)

adults —> acromegaly (large jaw, coarse facial features, large hands/feet)

38
Q

how does acromegaly present in adults?

A

result of excessive growth hormone, insidious onset (~12 years)

—> enlarged jaw, coarse facial features, large hands/feet, organ enlargement, joint pain (cartilage enlargement), CV disease

also presents with insulin resistance/ diabetes (GH is anti-insulin)

39
Q

Pt is a 36yo M presenting to his GP with joint pain. He notes he recently stopped fitting in his shoes and had to buy a size larger. He is well appearing but you note he has a very prominent jaw. Labs are indicative of diabetes. What is likely going on?

A

acromegaly: result of excessive growth hormone, insidious onset (~12 years)

—> enlarged jaw, coarse facial features, large hands/feet, organ enlargement, joint pain (cartilage enlargement), CV disease

also presents with insulin resistance/ diabetes (GH is anti-insulin)

40
Q

what kind of drug is octreotide, and what can it be used to treat (4)?

A

analog of somatostatin - suppresses release of growth hormone (somatotropin), can be used to treat acromegaly (note bony abnormalities/ joint symptoms do not regress)

can also be used to treat carcinoid syndrome, glucagonoma/insulinoma, and upper GI bleeding (decreases splanchnic blood flow)

41
Q

Cushing’s syndrome vs Cushing’s disease - which presents with hyperpigmentation?

A

Cushing’s syndrome: high levels of cortisol coming from adrenal gland, NOT driven by ACTH

Cushing’s disease: high levels of cortisol secretion induced by high levels of ACTH from pituitary gland - also presents with hyperpigmentation (recall POMC is precursor of both ACTH and MSH)

42
Q

what is proopiomelanocortin a precursor of?

A

aka POMC: produced by pituitary gland, precursor of both ACTH and alpha/beta/gamma MSH (melanocyte stimulating hormone)

(POMC gets split into multiple products)

43
Q

this hormone, produced by the paraventricular nuclei of the hypothalamus, causes milk release in response to suckling. what is?

A

oxytocin - released from posterior pituitary in response to afferent fibers in the nipple, triggers contraction of myoepithelial cells in the breast

44
Q

what are the therapeutic uses of pitocin during labor?

A

pitocin = synthetic oxytocin, which causes uterine contractions

can be used to 1. induce labor and 2. stop heavy postpartum uterine bleeding (via contraction of uterus)

45
Q

what are the most common genetic alterations found in non-spontaneous pituitary adenomas?

A

G-protein mutations, such as in GNAS gene which encodes Gs-alpha

GNAS mutation leads to constitutive activation of Gs-alpha —> persistent cAMP generation, unchecked cellular proliferation (~40% of somatotroph cell adenomas)

46
Q

How do pituitary adenomas appear histologically?

A

Cellular monomorphism - relatively uniform, polygon cells in sheets, cords, or papillae

Connective tissue is sparse

47
Q

hypopituitarism accompanied by evidence of posterior pituitary dysfunction in the form of diabetes insipidus is almost always of _____ origin

A

hypothalamic

48
Q

which type of lung cancer is known to cause ectopic secretion of ADH?

A

small-cell carcinoma - can induce SIADH (syndrome of inappropriate ADH secretion)

Endocrine (29 decks)

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