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Physiology II > E3- Random > Flashcards

E3- Random Flashcards

1
Q

Thyroid deficiency during gestation leads to what?

A

cretinism

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2
Q

In a hyperthyroid state is colloid is reabsorbed more or less?

A

More

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3
Q

What type of cells release calcitonin?

A

Parafollicular

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4
Q

What 2 things inhibit the Na/I symporter?

A

Perchlorate and thiocyanate inhibit

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5
Q

What are the effects of a low iodide diet?

A

NIS is increased to compensate for deficiency
Lack of iodide in the diet –> cannot make iodine –> cannot T3 or T4 –> hypothyroidism
A lack of thyroid hormones –> lack of negative feedback on the HPA –> ↑ TRH and ↑ TSH –> ↑ TSH causes goiter

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6
Q

What are the effects of Graves’ disease

A

Autoantibodies that mimic TSH
Leads to hyperthyroidism
Excessive thyroid hormones –> increased negative feedback on HPA –> ↓ TRH and ↓ TSH –> stimulation of growth causes goiter

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7
Q

What does iodide bind to for transport to/across the apical membrane

A

Pendrin

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8
Q

What is Pendred Syndrome

A

Goiter and hearing loss develop during childhood

If iodide intake is scarce, pts develop goiter and hypothyroidism

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9
Q

Iodide efflux from the cell into the colloid occurs through the what channel?

A

Iodide channel anoctamin-1

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10
Q

On the colloid side of the apical membrane, iodide is oxidized to iodine by what?

A

thyroid peroxidase (TPO)

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11
Q

What inhibits thyroid peroxidase (TPO)?

A

Propylthiouracil

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12
Q

What is the Wolff-chikoff effect?

A

Iodine metabolism can also be regulated independently of TSH
Occurs when plasma iodide levels are elevated
Elevated iodide levels inhibit organification to prevent excess thyroid hormone production

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13
Q

Iodinated tyrosine molecules fuse together to form thyroid hormones, this fusion is catalyzed by what?

A

thyroid peroxidase (TPO)

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14
Q

Following stimulation by TSH, what induces the follicular cell to engulf the colloid containing Tg, T3 and T4?

A

Megalin

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15
Q

Lysosomes target the engulfed colloid and what splits the iodinated products from thyroglobulin?

A

Proteases

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16
Q

In the plasma T3 and T4 bind to what?

A

Thyoxine-binding globulin (TBG)

T3 and T4 have a very high binding affinity for proteins; very little free circulating hormone

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17
Q

In the follicular cell, MIT and DIT are diiodinated by what?

A

Deiodinases

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18
Q

What is associated with higher Tg levels in the plasma?

A

Hyperthyroidism

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19
Q

T4 is converted to active __ by ___ ring deiodination via deiodinases type __

A

T4 is converted to active T3 by outer ring deiodination via deiodinases type 1 and 2

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20
Q

T4 is converted to inactive __ by ___ ring deiodination via deiodinase type __

A

T4 is converted to inactive rT3 by inner ring deiodination via deiodinase type 3

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21
Q

T3 and T4 enter cells by transporters.

OATP transporter has preference for which hormone?

A

T4

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22
Q

T3 and T4 enter cells by transporters.

MCT transporter has preference for which hormone?

A

T3

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23
Q

Mutations in this which thyroid hormone transporter class are associated with psychomotor retardation and thyroid hormone resistance?

A

MCT

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24
Q

Which thyroid hormone has a greater blinding affinity for thyroid receptors?

A

T3

T3 is 10x more potent for all actions!!

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25
Q

What are some calorigenic actions of thyroid hormones?

A

Increased oxygen consumption resulting in:
Increased basal metabolic rate (BMR)
Increased body temperature
Occurs in all tissues except the brain, gonads, and spleen

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26
Q

What are some metabolism actions of thyroid hormones?

A 
Increases:
-Glucose absorption from gut
-Gluconeogenesis
-Lipolysis
-Protein synthesis and proteolysis
(catabolic effect)
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27
Q

What are some CV actions of thyroid hormones?

A

T3 increases CO and ventilation
T3 is chronotropic and inotropic
T3 reduces vascular resistance

28
Q

What are some SNS actions of thyroid hormones?

A

Increased synthesis of B-adrenergic receptors in cardiac/skeletal muscles and adipocytes (heterologous up-regulation)

29
Q

What are some SNS actions of thyroid hormones?

A

Acts synergistically with GH and growth factors to promote bone formation
Stimulates protein synthesis
Maturation of CNS, axonal growth, and myelination
(anabolic effect)

30
Q

What layer produces mineralocorticoids (aldosterone)?

A

Zona glomerulosa

31
Q

What layer produces glucocorticoids (cortisol)?

A

Zona fasciculata

32
Q

What layer produces androgens (DHEA)?

A

Zona reticularis

33
Q

What layer produces EPI and NE?

A

Adrenal medulla

34
Q

The production of steroids is controlled by what?

A

ACTH

35
Q

The production of catecholamines is controlled by what?

A

SNS

36
Q

Precursor for all adrenocortical steroids is what?

A

Cholesterol

37
Q

Free cholesterol is transferred to the mitochondria, and then to the inner mitochondrial membrane by what?

A

STaR

38
Q

Cholesterol is converted to pregnenolone by what enzyme? (rate-limiting step and is dependent on STaR)

A

Desmolase

39
Q

What stimulates desmolase?

A

ATCH

40
Q

Cells in the zona glomerulosa are lacking what enzyme?

A

17a-hydrozylase; therefore, this zone does not produce glucocorticoids or androgens

41
Q

What is a type of primary hyperaldosteronism?

A

Conn’s syndrome

42
Q

What are the effects of Conn’s syndrome?

A

Increased Na reabsorption –> hypernatremia, fluid retention and HTN
Increased K secretion –> hypokalemia
Increased H secretion –> metabolic alkalosis
Low renin levels

43
Q

What are the effects of o 17a-hydroxylase deficiency?

A

Glucocorticoids and androgens are not produced
Steroid intermediates in the aldosterone pathway build up resulting in overproduction of 11-deoxycorticosterone and corticosterone
Corticosterone produces aldosterone-like effects (fluid retention, ↑ BP); the HTN inhibits renin secretion, causing aldosterone levels to be low
Leads to the same outcomes as with Conn’s syndrome
HTN
Hypokalemia
Metabolic alkalosis

44
Q

Cells in the zona fasiculate are lacking what enzymes?

A

17,20-lyase; therefore, this zone does not produce androgens

Aldosterone synthase; therefore, the synthesis of aldosterone cannot be completed

45
Q

Corticotrophin releasing hormone (CRH) stimulates corticotrophs to release ACTH. What are the effects of ACTH?

A

Stimulates adrenal gland growth
Transfers cholesterol into the mitochondria
Activates desmolase

46
Q

What inhibits CRH?

A

Cortisol

47
Q

Cortisol levels reflect a circadian and pulsatile release of ACTH. Greatest cortisol secretion occurs in the morning
In periods of stress, ACTH secretion is enhanced as a result of what?

A

Increased amplitude of CRH burst, rather than frequency

48
Q

What are the effects of cortisol?

A

Increase blood glucose by enhancing gluconeogenesis (essential for survival during fasting and stress)

  • Increases protein catabolism and lipolysis
  • Decreases glucose uptake by the tissues
49
Q

What hormone enhances responsiveness to alpha 1 receptors, inhibits bone formation, increases proteolysis in muscle, and has anti-inflammatory and immunosuppressive effects?

A

Cortisol

50
Q

Cells in the zona reticularis are lacking what enzyme?

A

Cells in this zone do not have 21B-hydroxylase; therefore, this zone does not produce aldosterone or cortisol

51
Q

What are adrenal androgens called?

A

17-ketosteroids

52
Q

What enzyme converts Progesterone to 11-Deoxycorticosterone?

A

21B-hydroxylase

53
Q

What enzyme converts corticosterone to aldosterone?

A

Aldosterone synthase

54
Q

What enzyme converts Pregnenolone to 17-hydroxypregnelone?

A

17a-hydroxylase

55
Q

What enzyme converts Progesterone to 17-hydroxypregnelone?

A

17a-hydroxylase

56
Q

What enzyme converts 17-hydroxypregnelone to DHEA?

A

17,20-lyase

57
Q

What enzyme converts 17-hydroxypregnelone to androstenedione?

A

17,20-lyase

58
Q

What enzyme converts 17-hydroxypregnelone to 11-Deoxycortisol?

A

21B-hydroxylase

59
Q

What are the effects of a 21B-hydroxylase deficiency?

A

Cortex does not produce glucocorticoids or mineralocorticoids, resulting in Na loss and hypoglycemia
Steroid intermediates build-up in the androgen pathway
ACTH levels are high because of a lack of feedback control of cortisol on the pituitary
Trophic effect of ATCH is seen
Increased levels of DHEA and androstenedione result in masculinization of female

60
Q 
Penis-like clitoris
Scrotum-like labia
Ovaries are present
Deepening of voice
Increased muscle mass
Amenorrhea and hirsutism
Are seen with what?
A

21B-hydroxylase deficiency

61
Q

Knowing that cortisol levels are higher than aldosterone and that cortisol binds with a higher affinity to produce mineralocorticoid activity, why does this not occur in normal conditions?

A
  1. Cortisol circulates bound to albumin and CBG, allowing only a small fraction of free hormone to cross cell membranes
  2. Aldosterone target cells have the enzyme 11B-hydroxysteroid dehydrogenase type II which converts cortisol into its inactive form (cortisone), which has less affinity to the MR
  3. Aldosterone dissociates from the MR more slowly than cortisol
62
Q

What type of MR and GR are predominant in the kidney and are specific for aldosterone?

A

Type I receptors

63
Q

What type of MR and GR are expressed in all cells and are specific for glucocorticoids?

A

Type II receptors

64
Q

11B-hydroxysteroid dehydrogenase type I (11B-HSD1)

promotes what conversion?

A

Cortisone to cortisol

65
Q

11B-hydroxysteroid dehydrogenase type II (11B-HSD2) promotes what conversion?

A

Cortisol to cortisone

Physiology II (3 decks)

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