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Endorine > Pituitary Physiology (5/15) > Flashcards

Pituitary Physiology (5/15) Flashcards

1
Q

Describe post pit development

A

The posterior pituitary (neurohypophysis) develops as an evagination of the ventral hypothalamus. From neural crest cells.

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2
Q

Describe ant pit dev

A

The anterior pituitary (adenohypophysis) is formed from evagination of pharyngeal ectoderm, which initially forms a duct called Rathke’s pouch and later fills in and closes. Develops over weeks 5-20

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3
Q

What TFs guide cellular differentiation during dev

A

Transcription factors that guide this process include Prop-1 and Pit-1. Inactivating mutations in these transcription factors will cause deficiencies in pituitary hormones.

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4
Q

List the 5 ant pit cell types

A
  1. Somatotrope
  2. Thyrotrope
  3. Lactotrope
  4. Gonadotrope
  5. Corticotrope
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5
Q

What does somatotrope produce?

A

Growth hormone (GH)

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6
Q

What does thryrotrope produce?

A

Thyrotropin (TSH)

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7
Q

What does lactotrope produce?

A

Prolactin (PRL)

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8
Q

What does gonadotrope produce?

A

LH and FSH

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9
Q

What does corticotrope produce?

A

Adrenocorticotropin (ACTH)

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10
Q

What are the 3 main groups of ant pit hormones?

A
  1. Glycoprotein hormones (TSH, LH, FSH, share alpha unit)
  2. ACTH (comes from POMC)
  3. GH and Prolactin (struc homology, can both activate prolactin receptor)
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11
Q

What does LH do?

A

Stimulates production and secretion of testosterone, preps uterus for implantation of fertilized ovum, stimulates ovulation

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12
Q

What does FSH do?

A

Stimulates egg and sperm production, stim estrogen synthesis

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13
Q

What does TSH do?

A

Stim secretion of thyroid hormones by thyroid gland and regulates thyroid cell proliferation and survival

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14
Q

What does ACTH do?

A

Stim synthesis and secretion of cortisol/adrenal cortex steroids by cortex of adrenal gland and proliferation and survival of adrenal cortex cells

No ACTH: atrophic adrenals
XS ACTH: hypertrophic adrenals

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15
Q

What does prolactin do?

A

Initiates milk production

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16
Q

What does human growth hormone do?

A

Stim growth and other effects post natally. Stimulates secretion of IGF-1 from the liver and other organs which is responsible for GH’s anabolic effects. Stimulates lipid and CHO metabolism

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17
Q

Which hormones have the same alpha subunit?

A

TSH, LH, FSH

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18
Q

What does loss of feedback regulation cause?

A

Pituitary trophic hormone hypersec and hyperplasia of pit cells like in severe hypothyroidism or hypoadrenalism

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19
Q

How do hypothalamic hormones get to the anterior pituitary?

A

Via the hypothalamic-pituitary portal system

Note: the portal system has two consecutive capillary beds. First carries hormones to the ant pit and does not reach the systemic circulation. Second carries hormones away from the ant pit and reaches systemic circulation

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20
Q

What are two rhythms in endocrinology?

A

Circadian (daily), most common

Ultradian (bursts, like GnRH)

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21
Q

Hypothyroidism caused by thyroid gland destruction can lead to hypertrophy of which gland?

A

Anterior pituitary…loss of negative feedback regulation

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22
Q

Describe CRH/ACTH system

A

Hypothal–>CRH (neg to hypothal)–>ant pit–>ACTH (neg on ant pit and hypothal)–>adrenal gland–>Cortisol (neg on ant pit and hypothal)

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23
Q

What are the extraadrenal actions of ACTH?

A

Stimulate lipolysis and inc skin pigmentation

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24
Q

What stimulates ACTH release?

A

CRH, stress, hypoglycemia, anxiety, depression, alpha and beta adrenergic agonists

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25
What pattern does ACTH get released normally?
Diurnal: peaks just before awakening with pulsatility
26
What inhibits ACTH?
Cortisol
27
To look for a deficiency in ACTH, when would you measure it?
Highest in the morning normally, measure then to see if its low
28
To look for excess in ACTH, when would you measure it?
Lowest at night normally, measure to see if its high
29
How do we measure hypothalamic hormones in the blood?
We don't ! It doesn't get to the systemic circulation
30
Someone wakes up stressed at 1am, what is their cortisol profile?
High ACTH and cortisol
31
Someone is sleeping at 1am, what is their cortisol profile?
Lower ACTH and Cortisol
32
Describe the growth hormone feedback loop
Hypothal-->GHRH (inhib hypothal) and Somatostatin (inhibits ant pit and hypothal)-->ant pit-->GH-->Liver-->IGF1 (inhibits ant pit and hypothal)
33
What is GHRH
Stimulatory hypothalamic hormone that is stim for somatotropes
34
What kind of rhythm is GHRH released in?
Episodic
35
What is GHRH release stimulated by/
Hypoglycemia, dietary protein, exercise
36
What is GHRH inhibited by?
IGF1 and GH
37
Is somatostatin confined to ant pit?
No also has receptors elsewhere like GI and pancreas, hypothalamus
38
What does somatostatin do?
Opposes GHRH action-inhibits GH release. Also inhibits TSH, PRL in pit and glucagon/insulin in panc
39
What somatostatin analogs are FDA approved?
Octreotide and Lantreotide
40
What is GH's rhythm and half life?
Pulatilie with a short half life of 6-20 min
41
What regulates the amplitude and freq of GH release
Age, gender, nutrition, sleep, body composition, stress, exercise
42
What does GH stimulate and how?
Stimulates post natal growth via indirect effects of IGF1
43
If you suspect excessive production of GH. What lab measurement would you order 1st
IGF1
44
What physiologic process will lead to decrease in GH production?
- reduction in GHRH secretion - Inc in somatostatin - Inc in IGF1
45
What inhibits prolactin?
Dopamine and dopamine agonists
46
Waht does prolactin do?
Negatively regulates LH and FSH via hypothalamus (GnRH) and stimulates milk production
47
Describe the prolactin axis
Hypothal-->PRFs, dopamine (neg to ant pit)-->ant pit-->Prl (neg to hypothal)-->mammary gland Also stimulating to ant pit is E2 from the ovary Neural stimulus also goes from mammary gland to hypothalamus
48
What hormone does prolactin stimulate?
NONE, does not stimulate a hormone and not a subject to feedback
49
What stimulates prolactin?
Breast stimulation, stress, estrogen, sleep, dopamine antag, TRH
50
Where is prolactin secreted from?
Lactotropes
51
What physiologic process can explain amenorrhea in a nursing woman?
High prolactin negatively regulates hypothalamic pituitary gonadal axis
52
What is more impt the concentration or pulsatility of GnRH?
Pulsatility and pulse freq are critical with greater freq and amplitude in puberty Pulsatile infusion stim LH and FSH sec Constant infusion inhibits LH and FSH sec to suppress gonadal fxn
53
What does high FSH, high LH, and low estrogen signal?
Menopause
54
What does TRH do?
Stim release of TSH and prolactin
55
What does TSH do?
TSH stimulates the conversion of T4-->T3. Responsive to intracellular T3 levels, when T3 is high, TRH receptors dec and thus response of thyrotrope to TRH decreases and thus TSH decreases
56
Describe the thyroid axis
Hypothal--> somatostatin (neg to ant pit) and TRH-->Ant pit-->TSH--->T4->T3 (neg regulate ant pit and hypothal)
57
What lab changes are expected when there is excessive production of TH (thyroxin) by overactive thyroid gland?
Low TSH, high thyroxin
58
What is the only axis in which the hypothalamus is primarily inhibitory?
Prolactin regulation by hypothalamus is primarily inhibitory
59
What are the two inhibitory hypothalamic factors?
Somatostatin and dopamine
60
Hormone activity depends on what?
quantity present and mode of release (impt for lab tests)

Endorine (24 decks)

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