EXAM #1: PITUITARY PHYSIOLOGY Flashcards

1
Q

What is short-loop feedback? Give an example.

A

Hypothalamus acting on anterior pituitary and vice versa

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2
Q

What is ultra short-loop feedback? Give an example.

A

Hypothalamus releases a hormone that acts on the hypothalamus

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3
Q

What is long-loop feedback? Give an example.

A

Target organ exerting negative feedback on the:

  • Anterior pituitary
  • Hypothalamus
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4
Q

What releasing/inhibiting hormones are made and released by the hypothalamus?

A

1) CRH= Corticotroptin-releasing hormone
2) TRH= Thyrotropin releasing hormone
3) GnRH= Gonadotropin-releasing hormone
4) GHRH= Growth hormone releasing hormone
5) GHIH/Somatostatin= Growth hormone inhibiting hormone
6) PIH= Prolactin-inhibiting hormone

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5
Q

What is the action of Corticotroptin-Releasing Hormone (CRH) on the anterior pituitary?

A

Release of ACTH

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6
Q

What is the action of Thyrotropin Releasing Hormone (TRH) on the anterior pituitary?

A
  • Release of Thyroid Stimulating Hormone (TSH)

- Secretion of Prolactin

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7
Q

What is the action of Gonadotropin-Releasing Hormone (GRH) on the anterior pituitary?

A

Release of LH and FSH

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8
Q

What is the action of Growth Hormone Releasing Hormone (GHRH) on the anterior pituitary?

A

Release of Growth Hormone

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9
Q

What is the action of Growth Hormone Inhibitory Hormone (GHIH) on the anterior pituitary?

A

Inhibition of GH release

*Note that this is also called Somatostatin

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10
Q

What is the action of Prolactin-Inhibiting Hormone on the anterior pituitary?

A

Causes the release of dopamine

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11
Q

Which hormones are made by hypothalamic cells and released by the posterior pituitary?

A

1) Vasopressin

2) Oxytocin

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12
Q

Where are posterior pituitary hormones made? (Know names of the two hypothalamic nuclei)

A

1) Supraoptic nucleus

2) Paraventricular nucleus (PVN)

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13
Q

List the anterior pituitary hormones.

A

1) ACTH
2) TSH
3) FSH
4) LH
5) GH
6) Prolactin

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14
Q

List the posterior pituitary hormones and give their functions.

A

1) Vasopressin

2) Oxytocin

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15
Q

Which three pituitary hormones have a common α subunit but different β subunits which determine hormone specificity?

A

1) TSH
2) LH
3) FSH

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16
Q

What is the effect of increased prolactin release on the release of GnRH?

A

Prolactin inhibits GnRH

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17
Q

How does increased prolactin release affect fertility?

A

Inhibiting GnRH causes infertility

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18
Q

Describe the effect of pregnancy on lactotropes.

A

Pregnancy results in hypertrophy and hyperplasia of the prolactin-secreting lactotrophs

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19
Q

Why does the effect of pregnancy on lactotropes make the pituitary more likely to suffer ischemia from postpartum hemorrhage?

A
  • Hypertrophy/hyperplasia causes enlargement of the anterior pituitary
  • Enlargement makes the pituitary more likely to suffer ischemia if there is HYPOTENSION s/p post-partum hemorrhage
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20
Q

What is Sheehan syndrome?

A

Ischemic necrosis of the pituitary associated with post-partum hemorrhage/hypotension

21
Q

Describe the different types of diabetes insipidus.

A

1) Neurogenic diabetes insipidus= problem in hypothalamus/posterior pituitary
2) Nephrogenic diabetes insipidus= problem in kidney
3) Acquired diabetes insipidus= lithium induced
4) Psychogenic diabetes insipidus= excessive water intake

22
Q

How could you distinguish the different types from each other and from polyuria caused by excessive water ingestion?

A
  • Water restrict the patient and measure urine osmolality*
  • Give the patient ADH**

*IF psychogenic, the urine should be MORE concentrated with water restriction

23
Q

Describe the action of oxytocin and the stimulus for the milk let down reflex.

A
  • Infant suckles and stimulates the nipple
  • Oxytocin is released
  • Milk let-down reflex initiated
24
Q

What is the role of oxytocin in childbirth.

A
  • Increased number of oxytocin receptors on uterus during pregnancy
  • Distension of cervix and contraction of uterus causes release of oxytocin

*Positive feedback increases contraction of the uterus

25
Q

Describe the metabolic functions of growth hormone. What is the effect of growth hormone on bone growth?

A

Metabolic

1) Increased protein synthesis
2) Increased release of FA and use of fats for energy
3) Decreased use of glucose/ insulin resistance

Bone= growth at the epiphyseal plates

26
Q

Describe the relationship between growth hormone and the insulin like growth factors. Where is each produced?

A
  • GH= anterior pituitary
  • IGF= hepatocytes

*GH requires IGF-1 to exert its action

27
Q

What is the other name for the insulin-like growth factors?

A

Somatomedins C

28
Q

Define term panhypopituitarism.

A

Inadequate or absent production of the anterior pituitary hormones

29
Q

Describe the effect of too much growth hormone.

A

Giantism vs. acromegaly

30
Q

Describe the effect of too little growth hormone.

A

Dwarfism

31
Q

How do the effects of too much GH differ if the problem is present from birth or occurs in adulthood.

A

Birth= giantism

Adult= acromegaly

32
Q

Describe the symptoms seen in patients with acromegaly.

A

After the epiphyseal plates close, excess GH causes:

  • Enlargement of the hands/feet
  • Protruding brow/jaw
  • Soft tissue swelling
  • Growth of internal organs
33
Q

Describe what is meant by primary hypothyroidism.

A

Problem is in the thyroid

34
Q

Describe what is meant by secondary hypothyroidism.

A

Problem in the pituitary i.e. deficient release of TSH

35
Q

Describe what is meant by tertiary hypothyroidism.

A

Problem in the hypothalamus i.e. deficient TRH

36
Q

Explain how primary hypothyroidism can cause hyperprolactinemia.

A
  • If T3/4 are low, body will compensate with increases TRH and TSH
  • TRH increases BOTH TSH and prolactin

*Thus, primary hypothyroid can lead to hyperprolactinemia

37
Q

What is the Median eminence?

A

Location in the hypothalamus where the portal vessels arise

38
Q

Describe the parts of the portal circulation between the hypothalamus and anterior pituitary.

A

Primary plexus= first part of circulation between hypothalamus and anterior pituitary

Secondary plexus

39
Q

What is the Hypothalamohypophysial tract?

A

Axons of the supraoptic and PVN that connect the hypothalamus to posterior pituitary

40
Q

What function is the associated with the VMN?

A

Satiety center

41
Q

What function is the associated with the lateral hypothalamus?

A

Hunger center

42
Q

What function is the associated with the anterior hypothalamus?

A

1) Thermoregulation–cooling

2) Thirst

43
Q

What function is the associated with the posterior hypothalamus?

A

Thermoregulation–heating

44
Q

What are the functions of ACTH?

A

1) Stimulation of cortisol synthesis and secretion
2) Increased melanin synthesis

*Also increases androgens and aldosterone

45
Q

What are the functions of TSH?

A

1) Increased synthesis and secretion of thyroid hormones (T3 and T4)
2) Growth of the thyroid
3) Stimulation the release of Prolactin

46
Q

What are the functions of FSH in males and females?

A

Females= growth of follicles in ovaries

Males= sperm maturation

47
Q

What are the functions of LH in males and females?

A

Males= stimulation of testosterone synthesis

Females=

1) Stimulation of ovulation
2) Formation of Corpus Luteum
3) Estrogen and progesterone synthesis

48
Q

What are the functions of Growth Hormone?

A

1) Stimulation of protein synthesis and overall growth

2) Production of Insulin-like Growth Factors

49
Q

What are the functions of Prolactin?

A

1) Breast development and milk production

2) Inhibits ovulation/ spermatogenesis