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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
Q

What pattern does ACTH get released normally?

A

Diurnal: peaks just before awakening with pulsatility

26
Q

What inhibits ACTH?

A

Cortisol

27
Q

To look for a deficiency in ACTH, when would you measure it?

A

Highest in the morning normally, measure then to see if its low

28
Q

To look for excess in ACTH, when would you measure it?

A

Lowest at night normally, measure to see if its high

29
Q

How do we measure hypothalamic hormones in the blood?

A

We don’t ! It doesn’t get to the systemic circulation

30
Q

Someone wakes up stressed at 1am, what is their cortisol profile?

A

High ACTH and cortisol

31
Q

Someone is sleeping at 1am, what is their cortisol profile?

A

Lower ACTH and Cortisol

32
Q

Describe the growth hormone feedback loop

A

Hypothal–>GHRH (inhib hypothal) and Somatostatin (inhibits ant pit and hypothal)–>ant pit–>GH–>Liver–>IGF1 (inhibits ant pit and hypothal)

33
Q

What is GHRH

A

Stimulatory hypothalamic hormone that is stim for somatotropes

34
Q

What kind of rhythm is GHRH released in?

A

Episodic

35
Q

What is GHRH release stimulated by/

A

Hypoglycemia, dietary protein, exercise

36
Q

What is GHRH inhibited by?

A

IGF1 and GH

37
Q

Is somatostatin confined to ant pit?

A

No also has receptors elsewhere like GI and pancreas, hypothalamus

38
Q

What does somatostatin do?

A

Opposes GHRH action-inhibits GH release. Also inhibits TSH, PRL in pit and glucagon/insulin in panc

39
Q

What somatostatin analogs are FDA approved?

A

Octreotide and Lantreotide

40
Q

What is GH’s rhythm and half life?

A

Pulatilie with a short half life of 6-20 min

41
Q

What regulates the amplitude and freq of GH release

A

Age, gender, nutrition, sleep, body composition, stress, exercise

42
Q

What does GH stimulate and how?

A

Stimulates post natal growth via indirect effects of IGF1

43
Q

If you suspect excessive production of GH. What lab measurement would you order 1st

A

IGF1

44
Q

What physiologic process will lead to decrease in GH production?

A
  • reduction in GHRH secretion
  • Inc in somatostatin
  • Inc in IGF1
45
Q

What inhibits prolactin?

A

Dopamine and dopamine agonists

46
Q

Waht does prolactin do?

A

Negatively regulates LH and FSH via hypothalamus (GnRH) and stimulates milk production

47
Q

Describe the prolactin axis

A

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
Q

What hormone does prolactin stimulate?

A

NONE, does not stimulate a hormone and not a subject to feedback

49
Q

What stimulates prolactin?

A

Breast stimulation, stress, estrogen, sleep, dopamine antag, TRH

50
Q

Where is prolactin secreted from?

A

Lactotropes

51
Q

What physiologic process can explain amenorrhea in a nursing woman?

A

High prolactin negatively regulates hypothalamic pituitary gonadal axis

52
Q

What is more impt the concentration or pulsatility of GnRH?

A

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
Q

What does high FSH, high LH, and low estrogen signal?

A

Menopause

54
Q

What does TRH do?

A

Stim release of TSH and prolactin

55
Q

What does TSH do?

A

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
Q

Describe the thyroid axis

A

Hypothal–> somatostatin (neg to ant pit) and TRH–>Ant pit–>TSH—>T4->T3 (neg regulate ant pit and hypothal)

57
Q

What lab changes are expected when there is excessive production of TH (thyroxin) by overactive thyroid gland?

A

Low TSH, high thyroxin

58
Q

What is the only axis in which the hypothalamus is primarily inhibitory?

A

Prolactin regulation by hypothalamus is primarily inhibitory

59
Q

What are the two inhibitory hypothalamic factors?

A

Somatostatin and dopamine

60
Q

Hormone activity depends on what?

A

quantity present and mode of release (impt for lab tests)

Endorine (24 decks)

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