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PHPY 303 > 02- Endocrinology > Flashcards

02- Endocrinology Flashcards

1
Q

Where is the thyroid gland located?

A

The anterior surface of the trachea

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2
Q

What types of cells is the thyroid gland made of?

A

Follicular cells and parafollicular cells

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3
Q

What do follicular cells of the thyroid gland secrete?

A

Thyroxine

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4
Q

What do parafollicular cells of the thyroid gland secrete?

A

Calcitonin

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5
Q

What does calcitonin do?

A

Regulates calcium and phosphate metabolism

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6
Q

Which essential trace element is required for thyroid hormone production?

A

Iodine

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7
Q

Where are the receptors for thyroid hormones?

A

In the nucleus

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8
Q

Where are thyroid hormones synthesized?

A

Follicular epithelial cells in the thyroid gland

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9
Q

What are the eight steps of the synthesis of thyroid hormones?

A
  1. Synthesis of thyroglobulin
  2. Iodide trapping
  3. Oxidation of iodide
  4. Iodination of thyrosine
  5. Coupling reactin
  6. Endocytosis of thyroglobulin
  7. Hydrolysis of T3 and T4 from thyroglobulin
  8. Deiodination
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10
Q

Where does the synthesis of thyroglobulin take place?

A

Thyroid follicular cells

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11
Q

What happens to thyroglobulin after it is made?

A

It is released into the follicular lumen

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12
Q

How is iodide transferred into the cells?

A

Sodium-iodide symporter

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13
Q

What enhances Na-I activity?

A

Thyroid stimulating hormone

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14
Q

What enzyme is responsible for the oxidation of iodide in the follicular epithelium?

A

Thyroid peroxidase

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15
Q

What does thyroid peroxidase catalyze the formation of?

A

Mono- and di- iodothyrosine

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16
Q

What happens to the iodinated thyroglobulin while it waits for a signal?

A

It is stored in the follicular lumen as colloid

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17
Q

What does thyroid peroxidase catalyze via the process of conjugation?

A

The formation of tetraiodothyronine

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18
Q

What comes together to form T4?

A

Two molecules of di-iodiothyrosine

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19
Q

What comes together to form T3?

A

One molecule of di-iodiothyrosine and one molecule of mono-iodiothyrosine

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20
Q

When does endocytosis of thyroglobulin occur?

A

When the thyroid gland is stimulated by thyroid stimulating hormone

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21
Q

What does lysosomal protease within the endocytotic vesicle do?

A

Hydrolyzes the peptide bonds to release T3 and T4 from thyroglobulin

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22
Q

What occurs in deiodination?

A

Uncoupled monoiodotyrosine and diiodotyrosine are attached to thyroglobulin and deiodinated inside follicular cells via thyroid deiodinase

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23
Q

What can iodine deficiency lead to?

A

Hypothyroidism and goiter

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24
Q

What can iodine deficiency cause in infants?

A

Cretinism

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25
Q

How do thyroid hormones impact basal metabolic rate?

A

They increase it by stimulating ineffective catabolic and anabolic cycles

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26
Q

What do thyroid hormones do in the bones?

A

Increase osetoblastic and osteoclastic activity

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27
Q

What do thyroid homrones do in the liver?

A

Increase triglyceride and cholesterol metabolism

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28
Q

What do thyroid hormones do in the brain?

A

Encourage axon growth and development

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29
Q

What do thyroid hormones do in the heart?

A

Have inotropic and chronotropic effects, and reduce smooth muscle resistance in vessels

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30
Q

What do thyroid hormones do in adipose tissue?

A

Increase lipolysis

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31
Q

What do thyroid hormones do in muscle?

A

Increase protein breakdown

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32
Q

What do thyroid hormones do in the gut?

A

Increase the rate of carnohydrate absorption

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33
Q

How is reverse T3 made and what is the problem with it?

A

The iodine is removed from the inner benzyl ring which makes it biologically inactive

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34
Q

What does 5’/3’-deiodinase do?

A

Removes an iodine from the outer benzene ring of T4 to produce T3

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35
Q

What does 5/3-deiodinase do?

A

Removes an iodine from the inner benzene ring of T4 to produce rT3

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36
Q

Where is type 1 5’/3’-deiodinase found and what does it do?

A

Present in the liver, kidneys, and thyroid

Generates most of the T3 that reaches general circulation

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37
Q

Where is type 2 5’/3’-deiodinase and what does it do?

A

Found in the pituitary, CNS, and placenta

Responsible for producing the T3 that is used in feedback inhibition

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38
Q

What are T3 and T4 usually bound to?

A

Thyroxine-binding globulin

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39
Q

Which two hormones influence feedback on TSH?

A

Somatostatin and dopamine

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40
Q

Where is the problem in a primary thyroid disorder?

A

The thyroid gland

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41
Q

Where is the problem in a secondary thyroid disorder?

A

The pituitary of hypothalamus

42
Q

Which disorders are associated with hypothyroidism?

A

Cretinism, myxedema, iodine-deficient goiter, and graves disease

43
Q

What makes up pancreatic cells?

A

Acini

44
Q

What makes up acini?

A

Islets of Langerhans

45
Q

How do islets use humoral communication?

A

The blood supply of islets courses outward from the center of the islet towards the periphery carrying glucose, humoral products, and other secretagogues

46
Q

How do islets uses cell-cell communication?

A

Communicate through gap junctions

47
Q

How do islets use neural communication?

A

Islets are innervated by sympathetic and parasympathetic nerves

48
Q

What kind of adrenergic stimulation causes excitation and which causes inhibition of islets?

A

Beta causes stimulation and alpha causes inhibition

49
Q

What do alpha cells secrete?

A

Glucagon

50
Q

What does glucagon do?

A

Causes glycogenolysis to increase blood glucose levels

51
Q

What causes glucagon secretion?

A

Reduced blood glucose, exercise, and protein rich meals

52
Q

What inhibits glucagon secretion?

A

Somatostatin and insulin

53
Q

What do beta cells secrete?

A

Insulin

54
Q

What does insulin do?

A

Lowers blood glucose, glycogenesis, and increased lipogenesis and protein synthesis

55
Q

What causes insulin secretion?

A

Elevated blood glucose, ACTH, ACh, glucagon, GIP, hCG, hCS, and hPL

56
Q

What inhibits insulin secretion?

A

Somatostatin

57
Q

What do delta cells secrete?

A

Somatostatin

58
Q

What does somatostatin do?

A

Inhibits secretion of hormones and reduces absorption of nutrients

59
Q

What inhibits somatostatin secretion?

A

Pancreatic polypeptide

60
Q

What do F cells secrete?

A

Pancreatic polypeptide

61
Q

What does pancreatic polypeptide inhibit?

A

Pancreatic digestive enzymes, somatostatin, contraction of the gall bladder, and intestinal motility

62
Q

What does insulin look like?

A

Two straight chains linked by disulfide bridges

63
Q

What tissues use GLUT 1?

A

Red blood cells and endothelial cells

64
Q

What tissues use GLUT2?

A

Renal tubular cells, hepatic cells, and pancreatic beta-cells

65
Q

What tissues use GLUT4?

A

Adipose tissue, skeletal muscle, and cardiac tissue

66
Q

What method of glucose administration is the most powerful insulin stimulant and why?

A

Oral intake causes an interaction with gastric inhibitory peptide hormone which also influences insulin

67
Q

How much more insulin is needed in a diabetic to get the same response as 5% insulin in a healthy person?

A

1000x

68
Q

Which insulin receptor chains are extracellular and which are membrane spanning?

A

The alpha chains are extracellular and the beta chains are membrane spanning

69
Q

What impacts the number of insulin receptors present on a cell?

A

Receptor synthesis, endocytosis of receptors, endocytosis by degradation

70
Q

Why do cells chronically exposed to insulin have fewer insulin receptors?

A

Downregulation

71
Q

What influences the ability of insulin to act on target cells?

A

The number of receptors, receptor affinity, and the receptor’s ability to transduce a signal

72
Q

What are insulin-receptor substrates important form?

A

The insulin signal transduction pathway

73
Q

Where is IRS-1 active?

A

Skeletal muscle

74
Q

Where is IRS-2 active?

A

The liver

75
Q

What does insulin do in the liver?

A

Promotes storage of glucose as glycogen, lipogenesis, and stimulates protein metabolism

76
Q

What does insulin do in the muscles?

A

Enhances the conversion of glucose to glycogen, increases glucose breakdown, and promotes the synthesis of proteins in the skeletal muscle

77
Q

What does insulin do in the adipose tissue?

A

Stimulates breakdown of glucose, promotes formation of triglycerides, and induces the synthesis of lipoprotein lipase

78
Q

What can cause an increase in nitric oxide production?

A

Insulin, C-peptide, and pro-insulin

79
Q

What does glucagon cause during hypoglycemia?

A

Glycogenolysis, gluconeogenesis, and ketogenesis

80
Q

How does human placental lactogen impact a pregnant mother?

A

Reduces insulin sensitivity, reduces utilization of nutrients, and enhances maternal lipolysis

81
Q

What are some microvascular complications associated with diabetes?

A

Retinopathy, nephropathy, and neuropathy

82
Q

What are some macrovascular complications of diabetes?

A

Coronary artery disease, stroke, and peripheral arterial disease

83
Q

What does cortisol do?

A

Increases plasma glucose levels, is an anti-inflammatory, optimizes the vascular responsiveness to catecholamines, and enhances glomerular filtration

84
Q

What does aldosterone do?

A

Promotes salt and water retention

85
Q

What do chromaffin cells produce?

A

Epinephrine and norepinephrine from tyrosine

86
Q

Where is cortisol produced?

A

The zona faciculata of the adrenal cortex

87
Q

What is cortisol bound to in the plasma?

A

Transcortin (corticosteroid-binding globulin)

88
Q

How does cortisol increase plasma glucose concentrations?

A

Activating gluconeogenesis, increasing protein catabolism, and increasing lipolysis

89
Q

How does cortisol act as an anti-inflammatory?

A

Increases the synthesis of lipocortin, inhibits the release of cytokines and interleukin-2, and reduces the proliferation of T-lymphocytes, inhibits the release of histamine, inhibits bradykinin and seretonin’s inflammatory effects, decreases eosinophil, basophil, and lymphocyte counts, and impairs cell-mediated immunity

90
Q

What kind of immunity are T-lymphocytes and B-lymphocytes involved in?

A

T-lymphocytes are involved in cytotoxic cell-mediated adaptive immunity
B-lymphocytes are involved in humoral or antibody driven adaptive immunity

91
Q

What is cushing syndrome?

A

Excess cortisol leading to truncal adiposity, hypertension, loss of subcutaneous adipose and connective tissue, loss of bone mineral, muscle weakness, and hyperglycemia

92
Q

What is Addison’s disease?

A

Insufficient cortisol causing adrenal insufficiency and hypocortisolism

93
Q

Where is aldosterone produced?

A

In the zona glomerulosa of the adrenal cortex

94
Q

What other elements are impacted due to the salt-water balance of aldosterone?

A

Potassium and hydrogen

95
Q

Where are adrenal andorgens produced?

A

The zona reticularis of the adrenal cortex

96
Q

What are examples of adrenal androgens?

A

Dehydroepiandrosterone and androstenedione

97
Q

What happens to adrenal androgens in males?

A

They are converted to testosterone in the testes

98
Q

What happens to adrenal androgens in females?

A

Converted into 17beta-estradiol by the granulosa cells of the ovarian follicle

99
Q

Which enzymes degrade catelcholamines?

A

Catelcholamine-O-methyltransferase and monoamine oxidase

100
Q

What stimulates the secretion of cortisol?

A

Corticotropin-releasing hormone from the hypothalamus stimulates the corticotrophs to secrete adrenocorticotropic hormone which stimulates adrenal cortex

PHPY 303 (3 decks)

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