1 - Pituitary and Thyroid Hormones Flashcards
(81 cards)
1
Q
The pituitary gland lies in a bony cavity called the _______
It is connected to the hypothalamus by ________
A
sella turcica
pituitary stalk
2
Q
The anterior pituitary is also known as:
The psosterior pituitary is also known as:
A
adenohypophysis
neurohypophysis
3
Q
List the six major hormones of the anterior pituitary
A
- growth hormone
- adrenocorticotropic
- TSH
- Prolactin
- FSH
- Luteinizing
4
Q
List the two major hormones of the posterior pituitary
A
- ADH
- Oxytocin
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)
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
7
Q
Where are posterior pituitary hormones synthesized?
A
Cell bodies in the hypothalamus
8
Q
Almost all pituitary secretion is controlled by the ______
A
hypothalamus, either through nervous or hormonal signalling
9
Q
Another word for pituitary is
A
hypophysial
10
Q
Prolactin inhibitory hormone is also known as _______
A
Dopamine
11
Q
All the major anterior pituitary hormones except GH exert heir effects by:
A
Stimulating target glands
12
Q
Where does GH exert its effects?
A
Directly on all or almost all tissues of the body
13
Q
What are two other names for GH?
A
Somatotropic hormone
Somatotropin
14
Q
GH promotes:
A
increased size, mitosis, and differentiation of cells
15
Q
GH has three metabolic effects:
A
- Enhances body protein
- Decreases fat stores
- Conserves carbohydrates
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
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
18
Q
Growth hormone is only effective if _____ and _____ are present
A
insulin
carbohydrates
19
Q
Function of osteoblasts:
Function of osteoclasts:
A
deposit new bone
remove old bone
20
Q
Does growth hormone stimulates osteoblasts or osteoclasts?
A
Osteoblasts
thickens the bones
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
22
Q
Growth hormone has a ____ duration
IGF-1 has a ______ duration
A
short (20 min)
long (20 hours)
23
Q
GH secretion follows a _____ pattern
A
pulsatile
24
Q
Starvation with protein deficiency will have what effect on growth hormone?
A
Stimulate secretion of GH
25
Exercise, excitement, and trauma have what effect on GH?
increased secretion
26
In severe conditions of protein malnutrition, why does it not work to just give adequate calories?
It has to be protein
If you give adequate calories via carbs, the level of GH won't change
27
\_\_\_\_\_\_ hormone is responsible for stimulating GH release
\_\_\_\_\_\_\_ hormone is responsible for supressing GH release
GHRH
Somatostatin (GHIH)
28
Where are GHRH and somatostatin stored?
The hypothalamus, in the same areas that are sensitive to blood glucose levels and satiety
29
Most of the control of GH is via _____ hormone
GHRH rather than somatostatin
30
ADH and Oxytocin are both synthesized in the \_\_\_\_\_\_
hypothalamus
31
Minute concentrations of ADH cause \_\_\_\_\_\_\_
Higher concentrations of ADH cause \_\_\_\_\_\_\_
water conservation
vasoconstriction
32
How does the body sense when ADH is needed to restore fluid balance?
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
33
The thyroid hormone secretes two hormones:
Thyroxine (T4)
Triiodothyronine (T3)
34
Complete lack of thyroid secretion decreases BMR by \_\_\_%
Extremely excessive thyroid secretion can raise BMR by \_\_\_%
40-50% below normal
60-100% above normal
35
Thyroid secretion is controlled by \_\_\_\_\_\_\_
which is secreted by \_\_\_\_\_\_\_
TSH
Anterior Pituitary
36
Besdies T3 and T4, what else does the thyroid secrete?
Calcitonin
37
Which is produced in larger quantities: Thyroxine or Triiodythonine?
Thyroxine, but it is the precursor to Triidothynonine, and pretty much all thyroxine gets converted to T3 in the tissues
38
Which is more potent: T3 or T4?
T3 is four times more potent, but is present in the blood in very low concentrations
39
The thyroid gland is comprised of large numbers of _____ that are filled with:
follicles
secretory substance called colloid
40
The major constituent of the colloid in thyroid cells is:
thyroglobulin, which contains the thyroid hormones
41
How much iodine is required per week to prevent deficiency?
1 mg/wk
50 mg/yr
42
How is iodine trapping acheived?
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
The rate of iodide trapping is mainly determined by:
the concentration of TSH
44
How is iodine transported into the cuboidal epithelial cell of the thyroid?
How is it transported into the follicle?
the sodium iodide pump
a chloride-iodid ion counter-transporter called pendrin
45
What is the role of iodine in formation of thyroid hormones?
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
If your thyroid stops making hormones, how long will it take for symptoms to show up?
2-3 months
47
Each thyroglobulin contains up to _____ thyroxine molecules and ___ T3 molecules
30
a few
48
How is thyroglobulin released into the blood stream?
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
What is the role of the deiodinase enzyme?
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
How are T3 and T4 circulated in the blood?
99% protein bound
The high affinity of plasma proteins for T3 and T4 allow slow release into the tissue cells
51
Once they enter the target cell, what happens to T3 and T4?
They are again bound to intracellular proteins and stored for
used slowly over a period of days or weeks
52
What is the onset and peak to T4?
T3?
2-3 days, 10-12 days
6-12 hours, 2-3 days
53
Why do the latency periods of T3 and T4 vary so intensely?
Mostly due to T3's relatively smaller affinity for plasma proteins
It's released more easily and more rapidly
54
What changes do thyroid hormones incite once they enter the cell?
Increases transcription of many genes
increases the size and number of mitochondria
Increases Na-K ATPase activity
55
When thyroid hormone levels rise, the concentrations of plasma cholesterol, phospholipids and triglycerides \_\_\_\_\_\_
decrease
The opposite is also true
56
Why is hypothyroidism associated with atherosclerosis?
Increased circulating plasma cholesterol level
57
How does thyroid hormone stimulate carb metabolism?
Increases rapid glucose uptake by cells
enhances glycolysis and gluconeogenesis
increased rate of absoprtion from GI tract
increased insulin secretion
58
How does thyroid hormone increase fat metabolism?
rapidly mobilizes lipids from fat tissue
59
Thyroid hormone increases the need for \_\_\_\_\_, and may cause a deficiency if repletion isn't present.
Vitamins
60
Why don't you lose weight when you have excess thyroid?
It also increases appetite
61
Why does the thyroid hormone cause increased blood flow and cardiac output?
Increased metabolism means increased release of metabolic end products, which causes vasodilation
Cardiac output increases to compensate
62
Why does the heart rate increase with thyroid hormone?
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
How does blood pressure change in response to thyroid hormone?
The MAP is unchanged, but the pulse pressure is greater in hyperthyroidism
64
How does thyroid hormone dysfunction effect menstruation?
Hyperthyroidism causes amenorrhea
Hypothyroidism causes menorrhagia and polymenorrhea
65
What are the five ways TSH effects the thyroid gland?
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
After TSH is released, how long does it take for T3 and T4 release to occur?
30 minutes
67
What intracellular signalling pathway does TSH utilize to effect thyroid cells?
cAMP- adenylyl cyclase
68
TSH release from the anterior pituitary is regulated by which hormone?
TRH from the hypothalamus
69
What intracellular signalling pathway does TRH utilize to release TSH from the Anterior pituitary?
Phospholipase second messenger system
70
What is one of the best known stimulants for TRH and TSH secretion?
Cold!
71
The anterior pituitary is composed of two main cell types:
Chromophobes (nonsecretory)
Chromophils (secretory)
72
What are the three categories of tropic hormones secreted by the anterior pituitary?
1. Corticotropin related hormones (ACTH, MSH)
2. Glycoproteins (LH, FSH, TSH)
3. Somatotropins (GH and Prolactin)
73
GH secretion from the anterior pituitary is controlled by two hormones from the hypothalamus:
1. GHRH (increases secretion)
2. Somatostatin (inhibits secretion)
74
When does growth hormone secretion peak?
adolescence
75
What is the difference between somatotropic hormones and somatomedins?
Name an example of each
Somatotropic hormones *induce* increased cellular function and reproduction (GH, Prolactin)
Somatomedins *promote* cell growth and division (IGFs)
76
How does IGF mediate GH function?
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
The major stimulating substance for ADH secretion is:
The major inhibitory stimulus is:
Glutamate
GABA
78
The effects of ADH may be inhibited by:
hypercalcemia
prostaglandin E
hypokalemia
79
Melatonin release is stimulated by ______ and inhibited by \_\_\_\_\_\_\_
exposure to dark
exposure to light
80
What is the function of the pineal gland?
Melatonin secretion
circadian rhythm
81
Why does hyperthyroidism cause cardiac hyperactivity?
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
