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Patho 2 > 1 - Pituitary and Thyroid Hormones > Flashcards

1 - Pituitary and Thyroid Hormones Flashcards

1
Q

The pituitary gland lies in a bony cavity called the _______

It is connected to the hypothalamus by ________

A

sella turcica

pituitary stalk

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2
Q

The anterior pituitary is also known as:

The psosterior pituitary is also known as:

A

adenohypophysis

neurohypophysis

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3
Q

List the six major hormones of the anterior pituitary

A
  1. growth hormone
  2. adrenocorticotropic
  3. TSH
  4. Prolactin
  5. FSH
  6. Luteinizing
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4
Q

List the two major hormones of the posterior pituitary

A
  1. ADH
  2. Oxytocin
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5
Q

Name the cell types of the anterior pituitary and the hormones they produce

A

Somatotropes - hGH

Corticotropes - ACTH

Thyrotropes - TSH

Gonadotropes - LH and FSH

Lactotropes - Prolactin (PRL)

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6
Q

Why are tumors that secrete hGH called acidophilic tumors?

A

Somatotropes stain strongly with acid dyes

These tumors have large numbers of somatotropes, so they stain strongly with acid dye

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7
Q

Where are posterior pituitary hormones synthesized?

A

Cell bodies in the hypothalamus

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8
Q

Almost all pituitary secretion is controlled by the ______

A

hypothalamus, either through nervous or hormonal signalling

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9
Q

Another word for pituitary is

A

hypophysial

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10
Q

Prolactin inhibitory hormone is also known as _______

A

Dopamine

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11
Q

All the major anterior pituitary hormones except GH exert heir effects by:

A

Stimulating target glands

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12
Q

Where does GH exert its effects?

A

Directly on all or almost all tissues of the body

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13
Q

What are two other names for GH?

A

Somatotropic hormone

Somatotropin

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14
Q

GH promotes:

A

increased size, mitosis, and differentiation of cells

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15
Q

GH has three metabolic effects:

A
  1. Enhances body protein
  2. Decreases fat stores
  3. Conserves carbohydrates
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16
Q

What effect does blood glucose level have on growth hormone?

A

increased BG = inhibition of GH secretion

decreased BG = stimulation of GH secretion

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17
Q

How does growth hormone effect amino acid and protein level?

A

enhances amino acid uptake and protein synthesis

reduces the breakdown of proteins

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18
Q

Growth hormone is only effective if _____ and _____ are present

A

insulin

carbohydrates

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19
Q

Function of osteoblasts:

Function of osteoclasts:

A

deposit new bone

remove old bone

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20
Q

Does growth hormone stimulates osteoblasts or osteoclasts?

A

Osteoblasts

thickens the bones

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21
Q

The growth effects of GH are probably the result of the action of _______

rather than the direct effects of GH

A

insulin-like growth factors

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22
Q

Growth hormone has a ____ duration

IGF-1 has a ______ duration

A

short (20 min)

long (20 hours)

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23
Q

GH secretion follows a _____ pattern

A

pulsatile

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24
Q

Starvation with protein deficiency will have what effect on growth hormone?

A

Stimulate secretion of GH

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25
Q

Exercise, excitement, and trauma have what effect on GH?

A

increased secretion

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26
Q

In severe conditions of protein malnutrition, why does it not work to just give adequate calories?

A

It has to be protein

If you give adequate calories via carbs, the level of GH won’t change

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27
Q

______ hormone is responsible for stimulating GH release

_______ hormone is responsible for supressing GH release

A

GHRH

Somatostatin (GHIH)

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28
Q

Where are GHRH and somatostatin stored?

A

The hypothalamus, in the same areas that are sensitive to blood glucose levels and satiety

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29
Q

Most of the control of GH is via _____ hormone

A

GHRH rather than somatostatin

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30
Q

ADH and Oxytocin are both synthesized in the ______

A

hypothalamus

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31
Q

Minute concentrations of ADH cause _______

Higher concentrations of ADH cause _______

A

water conservation

vasoconstriction

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32
Q

How does the body sense when ADH is needed to restore fluid balance?

A

Osmoreceptors in the hypothalamus sense osmolarity/tonicity by monitoring their cell size. If the cells are shrinking, they interpret that as hyperosmolar plasms

If they’re getting bigger, they interpret that as hypoosmolar plasma

When the osmolarity is too high, ADH is secreted

When osmolarity is too low, ADH secretion is inhibited

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33
Q

The thyroid hormone secretes two hormones:

A

Thyroxine (T4)

Triiodothyronine (T3)

34
Q

Complete lack of thyroid secretion decreases BMR by ___%

Extremely excessive thyroid secretion can raise BMR by ___%

A

40-50% below normal

60-100% above normal

35
Q

Thyroid secretion is controlled by _______

which is secreted by _______

A

TSH

Anterior Pituitary

36
Q

Besdies T3 and T4, what else does the thyroid secrete?

A

Calcitonin

37
Q

Which is produced in larger quantities: Thyroxine or Triiodythonine?

A

Thyroxine, but it is the precursor to Triidothynonine, and pretty much all thyroxine gets converted to T3 in the tissues

38
Q

Which is more potent: T3 or T4?

A

T3 is four times more potent, but is present in the blood in very low concentrations

39
Q

The thyroid gland is comprised of large numbers of _____ that are filled with:

A

follicles

secretory substance called colloid

40
Q

The major constituent of the colloid in thyroid cells is:

A

thyroglobulin, which contains the thyroid hormones

41
Q

How much iodine is required per week to prevent deficiency?

A

1 mg/wk

50 mg/yr

42
Q

How is iodine trapping acheived?

A

the sodium-iodide symporter cotransports one iodid alongw ith two sodium into the cell

Sodium is actively pumped out of the cell by the Na-K ATPase

It passes back through its concentration gradient through the sodium-iodid pump, carrying to iodine with it which are then trapped in the cell

43
Q

The rate of iodide trapping is mainly determined by:

A

the concentration of TSH

44
Q

How is iodine transported into the cuboidal epithelial cell of the thyroid?

How is it transported into the follicle?

A

the sodium iodide pump

a chloride-iodid ion counter-transporter called pendrin

45
Q

What is the role of iodine in formation of thyroid hormones?

A

Oxidized iodine binds with thyroglobulin and “organifies” it, assisted by a peroxidase enzyme

Tyrosine substrates are formed

Eventually they couple to form lots of T4 and a little bit of T3

46
Q

If your thyroid stops making hormones, how long will it take for symptoms to show up?

A

2-3 months

47
Q

Each thyroglobulin contains up to _____ thyroxine molecules and ___ T3 molecules

A

30

a few

48
Q

How is thyroglobulin released into the blood stream?

A

It isn’t

The apical surface of the thyroid cell forms pinocytic vesicles around thyroglobulin

These join up with lysosomes that break thyroglobulin into T3 and T4

T3 and T4 freely diffuse across the membrane into the blood

49
Q

What is the role of the deiodinase enzyme?

A

75% of the iodinated tyrosine never becomes thyroid hormone

When the vesicles digest thyroglobulin, these tyrosines are also freed from the thyroglobulin molecules

They are cleaved by a deiodinase enzyme to recycle that iodine to make more thyroid hormone

50
Q

How are T3 and T4 circulated in the blood?

A

99% protein bound

The high affinity of plasma proteins for T3 and T4 allow slow release into the tissue cells

51
Q

Once they enter the target cell, what happens to T3 and T4?

A

They are again bound to intracellular proteins and stored for

used slowly over a period of days or weeks

52
Q

What is the onset and peak to T4?

T3?

A

2-3 days, 10-12 days

6-12 hours, 2-3 days

53
Q

Why do the latency periods of T3 and T4 vary so intensely?

A

Mostly due to T3’s relatively smaller affinity for plasma proteins

It’s released more easily and more rapidly

54
Q

What changes do thyroid hormones incite once they enter the cell?

A

Increases transcription of many genes

increases the size and number of mitochondria

Increases Na-K ATPase activity

55
Q

When thyroid hormone levels rise, the concentrations of plasma cholesterol, phospholipids and triglycerides ______

A

decrease

The opposite is also true

56
Q

Why is hypothyroidism associated with atherosclerosis?

A

Increased circulating plasma cholesterol level

57
Q

How does thyroid hormone stimulate carb metabolism?

A

Increases rapid glucose uptake by cells

enhances glycolysis and gluconeogenesis

increased rate of absoprtion from GI tract

increased insulin secretion

58
Q

How does thyroid hormone increase fat metabolism?

A

rapidly mobilizes lipids from fat tissue

59
Q

Thyroid hormone increases the need for _____, and may cause a deficiency if repletion isn’t present.

A

Vitamins

60
Q

Why don’t you lose weight when you have excess thyroid?

A

It also increases appetite

61
Q

Why does the thyroid hormone cause increased blood flow and cardiac output?

A

Increased metabolism means increased release of metabolic end products, which causes vasodilation

Cardiac output increases to compensate

62
Q

Why does the heart rate increase with thyroid hormone?

A

It’s NOT just due to the increase in cardiac output

seems to have a direct excitatory effect on the heart

Often one of the first s/s of thyroid issues is heart rate

63
Q

How does blood pressure change in response to thyroid hormone?

A

The MAP is unchanged, but the pulse pressure is greater in hyperthyroidism

64
Q

How does thyroid hormone dysfunction effect menstruation?

A

Hyperthyroidism causes amenorrhea

Hypothyroidism causes menorrhagia and polymenorrhea

65
Q

What are the five ways TSH effects the thyroid gland?

A
  1. increases proeolysis of thyroglobulin
  2. increased activity of iodide pump
  3. increased iodination of tyrosine
  4. increased size and increased secretory activity of thyroid cells
  5. increased number of thyroid cells (plus changes them from cuboidal to columnar)
66
Q

After TSH is released, how long does it take for T3 and T4 release to occur?

A

30 minutes

67
Q

What intracellular signalling pathway does TSH utilize to effect thyroid cells?

A

cAMP- adenylyl cyclase

68
Q

TSH release from the anterior pituitary is regulated by which hormone?

A

TRH from the hypothalamus

69
Q

What intracellular signalling pathway does TRH utilize to release TSH from the Anterior pituitary?

A

Phospholipase second messenger system

70
Q

What is one of the best known stimulants for TRH and TSH secretion?

A

Cold!

71
Q

The anterior pituitary is composed of two main cell types:

A

Chromophobes (nonsecretory)

Chromophils (secretory)

72
Q

What are the three categories of tropic hormones secreted by the anterior pituitary?

A
  1. Corticotropin related hormones (ACTH, MSH)
  2. Glycoproteins (LH, FSH, TSH)
  3. Somatotropins (GH and Prolactin)
73
Q

GH secretion from the anterior pituitary is controlled by two hormones from the hypothalamus:

A
  1. GHRH (increases secretion)
  2. Somatostatin (inhibits secretion)
74
Q

When does growth hormone secretion peak?

A

adolescence

75
Q

What is the difference between somatotropic hormones and somatomedins?

Name an example of each

A

Somatotropic hormones induce increased cellular function and reproduction (GH, Prolactin)

Somatomedins promote cell growth and division (IGFs)

76
Q

How does IGF mediate GH function?

A

binds to IGF-1 receptors and mediates anabolic effect

binds to insulin receptors, providing insulin-like efffect on skeletal muscle (moves glucose into the muscle)

77
Q

The major stimulating substance for ADH secretion is:

The major inhibitory stimulus is:

A

Glutamate

GABA

78
Q

The effects of ADH may be inhibited by:

A

hypercalcemia

prostaglandin E

hypokalemia

79
Q

Melatonin release is stimulated by ______ and inhibited by _______

A

exposure to dark

exposure to light

80
Q

What is the function of the pineal gland?

A

Melatonin secretion

circadian rhythm

81
Q

Why does hyperthyroidism cause cardiac hyperactivity?

A

T3 stimulates the synthesis of alpha myosin havey chain, sarcolemmal ion pumps, and beta membrane receptors

more receptors = more sensitivity

the heart is overreacting to a normal amout of beta stimulation, and as a result it is beating harder and faster

Patho 2 (24 decks)

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