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MSI Unit VIII Endocrine/Reproductive > Vallano-Hypothalamus and Pituitary, Thyroid Phys, Thyroid ARS > Flashcards

Vallano-Hypothalamus and Pituitary, Thyroid Phys, Thyroid ARS Flashcards

1
Q

Steroid Hormone Properties:

  1. Storage pools?
  2. Interaction with cell membrane?
  3. Receptor location?
  4. Action?
  5. Response Time?
A
  1. None
  2. Diffusion through cell membrane
  3. Receptor in cytoplasm or nucleus
  4. Regulation of gene transcription (primarily)
  5. Hours to days (primarily)
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2
Q

Peptide-Amine Hormone Properties:

  1. Storage pools?
  2. Interaction with cell membrane?
  3. Receptor location?
  4. Action?
  5. Response Time?
A
  1. Secretory vesicles
  2. Binding to receptor on cell membrane
  3. Receptor on cell membrane
  4. Signal-transduction cascade(s) affect a variety of cell processes
  5. Seconds to minutes
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3
Q

Which type of hormone is typically stored and which is typically produced on demand?

A

Peptide hormones stored in secretory vesicles

Steroid hormones produced on demand

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4
Q

Which type of hormone typically up/down-regulates gene transcription?

A

Steroid hormones

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5
Q

Which type of hormone has a quicker response time?

A

Peptide hormone response time is rapid while steroid hormone response time is slower

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6
Q

The anterior pituitary gland is also called what?

The posterior pituitary gland is also called what?

A

Anterior: adenohypophysis
Posterior: neurohypophysis

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7
Q

How does the hypothalamus communicate with the anterior pituitary (adenohypophysis)?

A

The anterior pituitary gland is controlled by hormones secreted into the hypophyseal portal circulation, which does not enter the general systemic circulation

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8
Q

What are the 6 major trophic hormones that the anterior pituitary secrete?

A

FLAT PiG

FSH, LH, ACTH, TSH, Prolactin, i, GH

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9
Q

Feedback of hormones released from peripheral glands onto the hypothalamic-pituitary axis is called ________.
Feedback from anterior pituitary hormones (FLAT PiG), onto the hypothalamus is called ________.

A

Long loop feedback

Short loop feedback

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10
Q

Which is the major hormone that stimulates milk production during lactation?
What hormone stimulates its release?

A

Prolactin

TRH: Thyrotropic releasing hormone stimulates its release

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11
Q

Unlike other anterior pituitary hormones, prolactin is under tonic inhibitory control by ________.
Why is this important?

A

Dopamine (aka prolactin releasing factor, PRF)
This is important because prolactin exerts a negative feedback on its own release by enhancing dopamine release from the hypothalamis (short-loop)…therefore if the pituitary stalk is severed, prolactin levels will increase (hyperprolactinemia), which causes infertility

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12
Q

What are Neurophysins and what two hormones are carried by it to the posterior pituitary?

A

Neurophysins are carrier proteins that are released wit their associated hormones and carry Oxytocin and ADH (vasopressin) from hypothalamus to posterior pituitary

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13
Q

Which hormone promotes milk let-down (ejection) and uterine contractions?
What kind of hormone is it?
Where is it synthesized?

A

Oxytocin is a neuropeptide that is synthesized in the hypothalamus (PVN) and can be secreted in response to suckling, uterine contractions, sight/smell/sound of an infant, and orgasm

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14
Q

Which hormone promotes water reabsorption and vasoconstriction?
Where is is synthesized, stored, and released?

A

ADH (vasopressin) is synthesized mainly in supraoptic nuclei (also PVN) of hypothalamus and is stored and released from posterior pituitary

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15
Q

The release of growth hormone (GH) is under inhibitory control by what other hormone?

A

Somatostatin

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16
Q

________ is the only hormone under primarily negative control from the hypothalamus, via dopamine release.

A

Prolactin is the only hormone under primarily negative control from the hypothalamus, via dopamine release. Sectioning of the pituitary stalk therefore increases prolactin secretion, due to loss of dopamine action on lactotrope cells of the anterior pituitary.

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17
Q

Is Oxytocin released into portal or systemic circulation?
Posterior or anterior pituitary?
Where is it synthesized?

A

Oxytocin is released directly into the general circulation by the posterior pituitary gland but is synthesized in the paraventricular and supraoptic nuclei of the hypothalamus.
It is carried by axonal transport to the nerve endings in the posterior pituitary. Its actions include milk expulsion during breastfeeding and uterine contractions, although a physiological role in induction or progression of labor is not well established.

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18
Q

Where does thyroid hormone bind?

A

Thyroid hormone, vitamin D, and steroid hormones are lipophilic and readily diffuse into target cells, where they are bound by nuclear receptors, initiating gene transcription.

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19
Q

What two types of hormones bind membrane receptors?

A

Peptide hormones and catecholamines are bound by membrane receptors, initiating an intracellular signaling cascade that ultimately leads to regulation of cellular function.

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20
Q

Hypothalamic hormone secretion of Somatostatin has what effect on which hypophysial hormone(s)?

A

Hypophysial hormone:↓GH

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21
Q

Hypothalamic hormone secretion of Dopamine has what effect on which hypophysial hormone(s)?

A

Hypophysial hormone:↓Prolactin

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22
Q

Hypothalamic hormone secretion of CRH (corticotropin-releasing hormone) has what effect on which hypophysial hormone(s)?

A

Hypophysial hormone:↑ACTH

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23
Q

Hypothalamic hormone secretion of TRH has what effect on which hypophysial hormone(s)?

A

Hypophysial hormone:↑TSH

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24
Q

Hypothalamic hormone secretion: of GnRH has what effect on which hypophysial hormone(s)?

A

Hypophysial hormone:↑LH and FSH

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25
Q

The inhibitory hormone _________ is both synthesized and stored in the hypothalamus.

A

somatostatin

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26
Q

In patients with _______, there is an inappropriately low secretion rate of ADH in response to changes in plasma osmolality,

A

central diabetes insipidus

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27
Q

A defect in the gene that codes for GnRH causes production of an inactive peptide. What is the effect on function of the anterior pituitary?

A

GnRH is required for the anterior pituitary to produce and secrete both FSH and LH. The absence of GnRH will cause deficiency of both pituitary gonadotropins.

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28
Q

Why does a tumor that compresses the pituitary stalk lower plasma level of most anterior pituitary hormones even if its tissue survives?

A

Compression of the stalk blocks the flow of blood that carries hormones and factors secreted by hypothalamic cells to target cells of the anterior pituitary. Most anterior pituitary hormones are predominately controlled by releasing factors; prevention of their delivery to the anterior pituitary lowers secretion of the pituitary hormone.

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29
Q

An anterior pituitary tumor has caused hypogonadism and galactorrhea in a male. Which of the following hormones is most likely secreted in excess?

A

Excessive prolactin suppresses gonadotropin production, leading to hypogonadism. The prolactin directly stimulates production of milk; this may occur in males as well as females.

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30
Q

A patient undergoes laboratory testing that reveals that she is hyperprolactinemic. What could be the cause of elevated prolactin levels?

A

Prolactin-inhibiting factor, or dopamine, is released from the hypothalamus and acts to inhibit prolactin secretion from the anterior pituitary. A decrease in dopamine would result in elevated prolactin levels.

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31
Q

An experiment is conducted during which the pituitary stalk is severed. Secretion of which hormone would increase?

A

Severing the pituitary stalk would remove all influence of the hypothalamic hormones on the anterior pituitary. Because prolactin secretion is controlled primarily by dopaminergic inhibition from the hypothalamus, removing this inhibition would increase prolactin levels.

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32
Q

TRH (thyrotropic-releasing hormone) is released by ______, and its effects are to stimulate ________, which releases _________, which has effects on the _________, ultimately releasing _____.

A

TRH (thyrotropic-releasing hormone) is released by the hypothalamus, and its effects are to stimulate anterior pituitary, which releases TSH (thyroid stimulating hormone), which has effects on the Thyroid gland, ultimately releasing T4,T3

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33
Q

T3, T4 are released from ________ and through negative feedback, inhibit _______ & _________.

A

T3, T4 are released from Thyroid gland and through negative feedback, inhibit anterior pituitary & hypothalamus

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34
Q

What two substances exert inhibitory effects on TSH release?

A

Dopamine and somatostatin

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35
Q

Choose T3 or T4:

There is preferential synthesis of _____

A

T4

36
Q

What essential trace element does THs require, which normally exists as salt?

A

Iodine

37
Q

Choose T3 or T4:

The thyroid gland primarily secretes____

A

T4 (93%)

T3 and reverse T3 (7%)

38
Q

Most iodide is stored in the ______ in association with _______

A

Most iodide is stored in the thyroid gland in association with thyroglobulin

39
Q

T/F: The majority of circulating or tissue T3 is derived from T4

A

True

40
Q

Most circulating TH is bound to _________

A

thyroid-binding globulin (TBG)

Other TH binding proteins are albumin and transthyretin
A small amount of TH circulates in free form

41
Q

T/F: TH receptors are expressed in virtually all tissues of the body

A

True

42
Q

Once inside the cell, 5’/3’ monodeiodinase activity removes _____, converting ____ to _____

A

5’/3’ monodeiodinase activity removes iodine converting T4 to T3, so once inside the cell, the levels of T4 and T3 are about equal

43
Q

Of the total thyroid hormone bound to thyroid receptors, about ~90% is _______

A

T3

44
Q

______is typically used to treat hypothyroidism, because of its longer half-life and greater stability

A

T4

45
Q

Choose T3 or T4:

_____ has higher biologic potency

A

T3

46
Q

Choose T3 or T4:

The volume of distribution is higher

A

T3

47
Q

Overall, THs have slow onset and long duration of action, between T3/T4, which acts more rapidly?

A

T3

48
Q

The overall effect of THs is to increase _________

A

the basal metabolic rate and O2 comsumption

49
Q

What effect does TH have on glucose metabolism?

A

Increases glucose absorption
Increases gluconeogenesis
Increase lipolysis

50
Q

T/F: TH deficiency in infants results in growth retardation and mental retardation?

A

True

Growth remediation can be attenuated with T4 treatment

51
Q

TSH is significantly elevated in _________, due to lack of negative feed back of ______

A

TSH is significantly elevated in primary hypothyroidism due to lack of negative feed back by low levels of circulating T3/T4

52
Q

TSH is reduced in _________, due to excessive negative feedback by _______

A

Primary hyperthyroidism

T3, T4

53
Q

Primary thyroid disease refers to a problem in _________, whereas secondary disease refers to a problem with _____ in the ________

A

Primary thyroid disease refers to a problem in thyroid gland itself, whereas secondary disease refers to a problem with TSH in the anterior pituitary

54
Q

BMR Increases/decreases in hyperthyroidism?

A

Increases

55
Q

T/F: TH has only anabolic effects in multiple tissues?

A

False, it has both anabolic and catabolic effects

56
Q

What role does TSH play in the synthesis and regulation of thyroid tissue growth?

A

The thyroid gland is composed of follicular epithelial that syntehsize and store T3/T4 and release these hormones into circulation. The synthesis is controlled by TSH, which is under negative feedback from the thyroid hormones themselves. Thyroid-stimulating hormone (TSH) regulates many steps in the synthetic pathway, including iodide uptake by Na+-I- symporters ([NIS] or cotransporters). TSH upregulates NIS. TSH stimulates thyroid tissue growth.

57
Q

What effect on cholesterol is observed in hypothyroidism?

What about BMR?

A

Increased plasma cholesterol concentration is commonly observed in hypothyroidism.
BMR decreased

58
Q 
Choose T3/T4:
Nuclear receptors have a higher affinity for?
Secretion rate is higher?
Plasma concentration is higher?
half-life is longer?
Volume of distribution is higher?
A

In target tissues, nuclear receptors for thyroid hormones have a greater affinity for T3 than for T4.
T3 has a greater volume of distribution
The secretion rate, plasma concentration, half- life, and onset of action are all greater for T4 than for T3.

59
Q

Triiodothyronine (T3) and thyroxine (T4) have a multitude of peripheral effects. In which form are T3 and T4 most biologically active?

A

Unbound.
Blood binding proteins, such as albumin and thyroxine-binding globulin, are important in maintaining a circulating “pool” of triiodothyronine (T3) and thyroxine (T4). However, while bound, hormones such as T3 and T4 are not biologically active. Only free hormones can exert peripheral effects, and this is one reason why both the free and bound states of thyroid hormones are measured in the blood during a thyroid panel

60
Q

What is the difference between thyroglobulin (TG) and thyroid-binding globulin (TBG)

A

Thyroglobulin is a protein involved in thyroid hormone synthesis by the thyroid gland.
Thyroid-binding globulin is a blood binding protein that maintains a circulating pool of T3/T4

61
Q

Describe the biosynthesis of thyroid hormones

A

TSH regulates synthesis (and release) of thyroid hormones (THs). This process involves uptake of dietary iodide, synthesis of proteins (including TG), incorporation of iodide into TG (organification), and coupling of MIT/DIT to form T3/T4 (catalyzed by thyroid peroxidase, TPO).

62
Q

Thyroid hormone receptors bind to DNA in what form?

A

The receptor that binds to the DNA is preferentially a heterodimer of the TR and retinoid X receptor (RXR)

63
Q

What changes would be expected to occur with increased binding of a hormone to plasma proteins?

A

Increase in plasma reservoir for rapid replenishment of free hormone.
Protein-bound hormones are biologically inactive and cannot be metabolized. Thus, an increase in protein binding would tend to decrease hormone activity and plasma clearance and increase the half-life of the hormone. Free hormone is also responsible for negative feedback inhibition of hormone secretion. Therefore, a sudden increase in hormone binding to plasma proteins would decrease negative feedback. Protein binding of hormones does, however, provide a reservoir for the rapid replacement of free hormone.

64
Q

A patient is administered sufficient thyroxine (T4) to increase plasma levels of the hormone severalfold.
What sets of changes to heart rate, respiratory rate, and cholesterol concentration is most likely in this patient after several weeks of T4 administration?

A

Increased heart rate, increased respiratory rate, and decreased cholesterol concentration are all responses to excess thyroid hormone.

65
Q

In hyperthyoridism, what is a concern with muscles?

What about B-adrenergic receptors?

A

In hyperthyroidism muscle wasting occurs because proteolysis outweighs synthesis.
Increased expression of B-adrenergic receptors result in enhanced sensitivity to epi/norepi

66
Q

In primary hypothyroidism, what are the effects on T4, TSH, and TRH?

A 
T4: ↓
TSH: ↑ 
TRH: ↑ 
Thyroid antibodies: Positive
Hashimoto's thyroiditis is most common cause...patients have reduced T4, which leads to increased TSH due to reduced negative feedback, but the thyroid gland cannot respond to elevated TSH levels because it is being destroyed by anti-thyroid antibodies
67
Q

In primary hyperthyroidism (Grave’s disease), what are the effects on T4, TSH, and TRH?

A

T4: ↑
TSH: ↓
TRH: ↓

68
Q

In secondary hypothyroidism (pituitary hypothyroidism), what are the effects on T4, TSH, and TRH?

A

T4: ↓
TSH: ↓
TRH: ↑

69
Q

In secondary hyperthyroidism (pituitary hyperthyroidism), what are the effects on T4, TSH, and TRH?

A

T4: ↑
TSH: ↑
TRH: ↓

70
Q

Primary/secondary Hypo-/hyper-thyroidism?
T4: ↑
TSH: ↑
TRH: ↓

A

secondary hyperthyroidism (pituitary hyperthyroidism)

71
Q

Primary/secondary Hypo-/hyper-thyroidism?
T4: ↓
TSH: ↓
TRH: ↑

A

secondary hypothyroidism (pituitary hypothyroidism)

72
Q

Primary/secondary Hypo-/hyper-thyroidism?
T4: ↑
TSH: ↓
TRH: ↓

A

primary hyperthyroidism (Grave’s disease)

73
Q 
Primary/secondary Hypo-/hyper-thyroidism?
T4: ↓
TSH: ↑ 
TRH: ↑ 
Thyroid antibodies: Positive
A

Primary hypothyroidism
Hashimoto’s thyroiditis is most common cause…patients have reduced T4, which leads to increased TSH due to reduced negative feedback, but the thyroid gland cannot respond to elevated TSH levels because it is being destroyed by anti-thyroid antibodies

74
Q

Which of the following is characteristic of a patient with Hashimoto’s thyroiditis?

A. Elevated serum TSH and TSH receptor antibodies
B. Elevated serum TSH and thyroid antibodies
C. Reduced serum TSH and reduced serum T3 & T4
D. Elevated serum TRH and reduced serum TSH

A

B. Elevated serum TSH and thyroid antibodies
Hashimoto’s thyroiditis is a common autoimmune disorder characterized by production of antithyroid antibodies (e.g. against thyroid peroxidase) that gradually destroy the gland. The antibodies interfere with synthesis of THs which are reduced as a consequence. Circulating TSH is increased due to less negative feedback by THs. However, the increased TSH cannot overcome the destructive effects of the thyroid antibodies (MLV).

75
Q

Which of the following is used to treat Graves disease?
A. Very high levels of iodine (Wolff-Chaikoff effect)
B. Iodinated iodine to destroy the gland (131I-)
C. Antithyroid agents such as PTU
D. Surgical removal of gland (thyroidectomy)
E. All of the above

A

E. All of the above

76
Q

Which one of the following symptoms is characteristic of hypothyroidism in the adult?
A. warm, moist skin
B. increasing muscle mass and strength
C. Exophthalmos
D. a deterioration of the thermoregulatory responses to cold
E. an increased ability to sweat in response to warming

A

D. a deterioration of the thermoregulatory responses to cold
Cold intolerance is associated with hypothyroidism.

Warm, moist skin, heat intolerance (not cold intolerance), increased sweating, and exophthalmos are associated with hyperthyroidism of Grave’s disease.

77
Q

Lethargy and myxedema are signs of hyper/hypothyroidism?

A

Lethargy and myxedema are signs of hypothyroidism

78
Q 
Which of the following findings would likely be reported in a patient with a deficiency in iodine intake?
A. Weight loss
B. Nervousness
C. Increased sweating
D. Increased synthesis of thyroglobulin
E. Tachycardia
A

D. Increased synthesis of thyroglobulin
Because iodine is needed to synthesize thyroid hormones, the production of thyroid hormones is impaired if iodine is deficient. As a result of feedback, plasma levels of thyroid-stimulating hormone increase and stimulate the follicular cells to increase the synthesis of thyroglobulin. This results in a goiter.

Increased metabolic rate, sweating, nervousness, and tachycardia are all common features of hyperthyroidism, not hypothyroidism due to iodine deficiency.

79
Q 
Which of the following would least likely be associated with thyrotoxicosis?
A. Tachycardia
B. Increased appetite
C. Somnolence
D. Increased sweating
E. Muscle tremor
A

C. Somnolence
Thyrotoxicosis indicates the effects of thyroid hormone excess. Thyroid hormone excites synapses. In contrast, somnolence is characteristic of hypothyroidism. Tachycardia, increased appetite, increased sweating, and muscle tremor are all signs of hyperthyroidism.

80
Q 
Untreated goiter is associated with:
A. hyperthyroidism
B. hypothyroidism
C. euthyroidism
D. hyperthyroidism and hypothyroidism
E. hyperthyroidism, hypothyroidism, and euthyroidism
A

hyperthyroidism, hypothyroidism, and euthyroidism

81
Q

__________ is an autoimmune disorder with the production of antithyroid antibodies that gradually destroy the gland, resulting in hypothyroidism….what is the name of the disease and what are the levels of TSH and TH?

A

Hashimoto’s thyroiditis-most common form of primary hypothyrodism
TSH is elevated but TH remains normal

82
Q 
Causes of hypothyroidism include:
A. Autoimmune thyroiditis
B. Surgery for hyperthyroidism
C. Iodide deficiency
D. Decreased TRH or TSH
E. All of the above
A

all of the above

83
Q

A patient presents with tachycardia and heat intolerance. You suspect Graves’ disease. Which of the following is not consistent with your diagnosis?
A. Increased total and free T4
B. Suppressed plasma [TSH]
C. Exophthalmos
D. Goiter
E. Decreased thyroid radioactive iodine uptake

A

E. Decreased thyroid radioactive iodine uptake
In Graves’ disease, antibodies against the TSH receptor in the thyroid gland stimulate many of the steps in the synthesis of thyroid hormones, including increased iodine uptake. Due to excessive stimulation of the gland, the thyroid gland hypertrophies and secretes increased amounts of thyroid hormones. High circulating levels of thyroid hormones inhibit TSH secretion due to negative feedback inhibition. The antibodies present in Graves’ disease also cause pathological changes in the tissue surrounding the eyes, leading to protrusion of the eyeballs.

84
Q

Thyrotoxicosis or Grave’s disease is typically characterized by:
A. Elevated serum T3, T4, and TSH
B. Elevated serum T3, T4 and thyroid antibodies
C. Elevated serum T3, T4, and TSH receptor antibodies
D. Elevated serum T3, T4, and non-toxic goiter
E. Reduced serum T3, T4, and elevated serum TSH

A

C. Elevated serum T3, T4, and TSH receptor antibodies
Grave’s disease is the most common form of hyperthyroidism. It is an autoimmune disorder characterized by high circulating titers of TSH receptor antibodies (sometimes called LATS or thyroid stimulating antibodies). These antibodies stimulate the TSH receptors on the thyrocytes to a greater extent than TSH itself, leading to increased synthesis and release of TH. The increased THs feedback to reduce TRH and TSH release from the hypothalamus and anterior pituitary, but the continued presence of the TSH receptor antibodies over-ride this compensatory effect (MLV).

85
Q

TSH receptor antibodies are associated with what disease?

A

Graves disease (thyrotoxicosis)-primary hyperthyroidism

86
Q

The following symptoms are typically observed in thyrotoxicosis or Graves disease:
A. Warm moist skin, elevated BMR, & heart palpitations
B. Heat intolerance, muscle wasting, & lethargy
C. Exophthalmos, nervousness, and constipation
D. Muscle wasting, cold intolerance & tachycardia

A

A. Warm moist skin, elevated BMR, & heart palpitations
Common symptoms of Graves disease include: nervousness, irritability, insomnia, goiter (toxic), increased BMR, heart palpitations/tachycardia, warm/moist skin, heat intolerance, fine tremor, muscular weakness (wasting), increased appetite, diarrhea (or loose stools), altered menstrual cycles. Exophthalmos is common in Grave’s disease (MLV).

87
Q 
A 58-year-old woman complained of lethargy and weight gain over the past year. Further investigation revealed a painless goiter, thick coarse skin, peripheral edema, and low iodine levels. Which of the following most likely describes this patient's diagnosis and plasma thyroid-stimulating hormone (TSH) level?
A. Primary hyperthyroidism, high TSH
B. Primary hyperthyroidism, normal TSH
C. Primary hyperthyroidism, low TSH
D. Primary hypothyroidism, high TSH
E. Primary hypothyroidism, normal TSH
F. Primary hypothyroidism, low TSH
A

Primary hypothyroidism, high TSHResponse Feedback:

Iodine deficiency prevents normal production of thyroid hormone by the thyroid gland, producing primary hypothyroidism. Lack of negative feedback inhibition by thyroid hormone on the hypothalamus and pituitary results in high TSH levels.

MSI Unit VIII Endocrine/Reproductive (10 decks)

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