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PHGY-210 > Endocrinology - Lecture 3 > Flashcards

Endocrinology - Lecture 3 Flashcards

1
Q

What is the parathyroid hormone secreted from?

A

parathyroid chief cells in the thyroid

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2
Q

How many parathyroid glands are there and where are they located?

A

4, located on the back side of the thyroid

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3
Q

What happens to plasma calcium levels when parathyroids are removed?

A

there is a severe drop = convulsions and death

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4
Q

What is the structure of parathyroid hormone?

A

N-terminal 34 amino acid

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5
Q

What is the larger protein that undergoes proteolytic cleavage to produce parathyroid hormone?

A

preproparathyroid hormone

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6
Q

What is the half-life of parathyroid hormone?

A

3-18 minutes

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7
Q

What is the main function of the parathyroid hormone?

A

increase the concentration of plasma calcium

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8
Q

What does PTH do to bone resorption?

A

it increases bone demineralization

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9
Q

What does PTH do to the kidneys?

A

it increases the reabsorption of Ca++ in proximal convoluted tubule

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10
Q

What does PTH do to vitamin D synthesis?

A

stimulates the conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3

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11
Q

Where does PTH stimulate the conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3?

A

in the kidney

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12
Q

What does PTH do to the gut?

A

it facilitates the absorption of Ca++ from the gut

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13
Q

What does PTH use in the gut to facilitate the absorption of Ca++?

A

1,25D3

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14
Q

What controls PTH release?

A

the circulating concentration of calcium

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15
Q

What is the mechanism of PTH activity?

A

it binds to cognate receptor on target cells

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16
Q

What is hypoparathyroidism?

A

low levels of PTH in circulation

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17
Q

What are the 3 symptoms of hypoparathyroidsim?

A
  1. hypocalcemia
  2. decreased vitamine D production
  3. tetany
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18
Q

What level of calcium needs to be present in the body for there to be muscle spasms in hypoparathyroidism?

A

<7mg/100mL

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19
Q

What is the treatment for hypoparathyroidism?

A

administration of 1,25-dihydroxyvitamin D and calcium supplements

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20
Q

What is hyperparathyroidism?

A

parathyroid adenoma of parathyroid producing too much PTH

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21
Q

What two substances are produced too much in hyperparathyroidism?

A
  1. PTH
  2. 1,25D3
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22
Q

What does high PTH stimulate in hyperparathyroidism?

A

bone resorption and calcium reabsorption from the kidney

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23
Q

What does 1,25D3 increase in hyperparathyroidism?

A

calcium absorption from the intestines

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24
Q

How are the levels of calcium describes in hyperparathyroidism?

A

elevated

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25
Q

What is a common symptom of hyperparathyroidism?

A

kidney stones

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26
Q

What are the symptoms of severe cases of hyperparathyroidism?

A

cardiac arrhythmias, depressed neuromuscular excitability, calcium deposition on walls of blood vessels and cartilaginous regions of bones

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27
Q

What is the treatment for hyperparathyroidism?

A

removal of affected parathyroids and replacement therapy of 1,25D3 and Ca++

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28
Q

How can we get vitamin D from our diet?

A

cod liver oil, fatty fish

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29
Q

Why is vitamin D not a vitamin?

A

because it can be synthesized from a cholesterol metabolite

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30
Q

What are the 3 steps in the synthesis of vitamin D?

A
  1. UVB light + 7-dehydrocholesterol in the skin
  2. 25-hydroxylation in liver
  3. 1-hydroxylation in kidney and several peripheral tissues -> 1,25-dihydroxyvitamin D3
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31
Q

What is the primary function of vitamin D?

A

increases calcium absorption from the intestine

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32
Q

What are the 2 secondary functions of vitamin D?

A
  1. regulates immune system (protects against infection, anti-inflammatory)
  2. anticancer properties
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33
Q

When is vitamin D synthesis increases?

A

in conditions of low calcium when PTH is also increases

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34
Q

When is vitamin D synthesis decreased?

A

when calcium is high

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35
Q

What is Rickets?

A

absence fo UVB leading to vitamin D deficiency and deficient bone mineralization

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36
Q

What does low vitamin D lead to in adults?

A

osteomalacia

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37
Q

What is calcitonin made of?

A

32 amino-acid calcium-loweing peptide hormone

38
Q

Where is calcitonin manufactured?

A

in parafollicular cells of the thyroid gland

39
Q

What is the function of calcitonin?

A

lowers plasma calcium

40
Q

How does calcitonin lower plasma calcium?

A
  1. promoting transfer of Ca++ from blood to bone
  2. increasing urinary excretion of Ca++
41
Q

Rise in plasma Ca++ ___ the release of calcitonin.

A

increases

42
Q

Decrease in plasma calcium concentration ___ the release of calcitonin.

A

decreases

43
Q

Calcitonin is of ___ importance than PTH and 1,25D3.

A

lesser

44
Q

Does the absence of calcitonin compromise calcium homeostasis?

A

no

45
Q

Where are adrenal glands located?

A

adjacent to the upper surface of the kidneys

46
Q

Are adrenal glands heavier in males or females?

A

males

47
Q

What are the 2 tissues found in the adrenal glands?

A

cortex and medulla

48
Q

What is the histologic appearance of the cortex?

A

large-lipid containing epithelial cells

49
Q

What is the histologic appearance of the medulla?

A

chromaffin cells-fine brown granules when fixed with potassium bichromate

50
Q

What is the origin of the cortex?

A

derived from mesoderm

51
Q

What is the origin of the medulla?

A

derived from the neural crest

52
Q

What is the function of the cortex?

A

produces steroid hormones

53
Q

What are the 3 hormones that the cortex produces?

A
  1. glucocorticoids
  2. mineralocoirticoids
  3. progestins
54
Q

What are the 4 hormones that the medulla produces?

A
  1. catecholamines
  2. epinephrine
  3. norepinephrine
  4. some peptide hormones
55
Q

What are the 3 layers of the adrenal cortex called?

A
  1. zona glomerulosa
  2. zona fasciculata
  3. zona reticularis
56
Q

What does the zona glomerulosa produce?

A

mineralocorticoids (aldosterone)

57
Q

What does the zona fasciculata produce?

A

glucocorticoids (cortisol)

58
Q

What does the zona reticularis produce?

A

glucocorticoids, progestins, androgens and estrogens

59
Q

What is the synthesis of adrenal steroids controlled by?

A

adrenocorticotropin ACTH

60
Q

Which zone is 18-hydroxylase present in?

A

zona glomerulosa

61
Q

Which zone is 17a-hydroxylase not present in? Why?

A

zona glomerulosa, because this zone does not produce glucocorticoids

62
Q

What is the function of steroid hormones?

A

to regulate the transcription of hormone/receptor specific target genes

63
Q

What are the 2 functions of aldosterone?

A
  1. increases the reabsorption of Na+ by the kidney
  2. affects the plasma concentration of K+ and H+
64
Q

What is an example of a glucocorticoid?

A

cortisol (humans), corticosterone (rodents)

65
Q

Which steroid hormone has more of an effect on salt retention?

A

aldosterone > cortisol

66
Q

How do glucocorticoids have an effect on protein and carbohydrate metabolism?

A

stimulate the synthesis of a number of gluconeogenic enzymes in hepatocytes, and several
enzymes that breakdown proteins in muscle and other tissues

67
Q

What does cortisol do to gluconeogenesis and glucose oxidation?

A

gluconeogenesis: increased
glucose oxidation: decreased

68
Q

Since glucocorticoids increase blood glucose levels, what happens to secreted insulin?

A

it increases

69
Q

What is increased blood glucose due to excess of glucocorticoid activity known as?

A

adrenal diabetes

70
Q

What happens if adrenal diabetes is prolonged?

A

it leads to true diabetes mellitus

71
Q

What do glucocorticoids do to the levels of lipolytic enzymes in the adipose tissue cells?

A

they maintain or increase them

72
Q

What does excess of glucocorticoids lead to in lipid metabolism?

A

hyperlipidemia and hypercholesterolemia

73
Q

What do glucocorticoids do to
1. inflammatory responses
2. atrophy of the lymphatic system
3. circulating lymphocytes
4. antibody formation
5. histamine formation

A
  1. decrease
  2. increase
  3. decrease
  4. decrease
  5. decrease
74
Q

What steroid hormone is used in organ transplantation?

A

glucocorticoids

75
Q

Through the protein catabolic effect of glucocorticoids, what do they do to the protein matrix of bones?

A

they decrease it

76
Q

What does glucocorticoids increase the loss of in bone which can lead to osteoporosis?

A

Ca++

77
Q

What is ACTH synthesized as part of?

A

proopiomelanocortin (POMC)

78
Q

What controls the feedback of cortisol secretion? (2)

A

hypothalamus and anterior pituitary

79
Q

What happens to ACTH secretion in cases of enzyme deficiencies?

A

it is unchecked

80
Q

What is caused due to enzyme deficiencies where cortisol is not produced?

A

congenital adrenal hyperplasia

81
Q

What is the treatment for congenital adrenal hyperplasia?

A

administration of cortisol

82
Q

Why is administration of cortisol used to treat congenital adrenal hyperplasia?

A

a) it corrects the deficiency
b) normalizes the ACTH secretion

83
Q

What 2 membranes does ACTH bind to?

A

zona fasciculata and zona reticularis

84
Q

What causes an increased production of cyclic AMP?

A

stimulation of adenylyl cyclase

85
Q

What does cyclic AMP activate?

A

steroidogenic enzymes

86
Q

What happens when steroidogenic enzymes are activated?

A

increase in synthesis and release of steroid hormones

87
Q

When is the diurnal rhythm of ACTH and cortisol secretion at a minimum and maximum?

A

minimum: midnight
maximum: in the morning

88
Q

What can the rhythm of plasma cortisol and ACTH be abolished by?

A

stress and Cushing’s disease

89
Q

What does stress stimuli (physical or psychological) increase the synthesis and release of?

A

CRH, ACTH and cortisol

90
Q

Why can the release of cortisol during stress be advantageous?

A

because it provides energy and amino acids through the breakdown of tissue proteins

91
Q

Why can the release of cortisol during stress be disadvantageous?

A

because it can inhibit wound healing

92
Q

Prolonged stress would maintain high levels of ___ which could lead to increased ___ ___, decreased ___ ___ and ___ ___

A

glucocorticoids, blood glucose, immune responses, bone loss

PHGY-210 (36 decks)

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