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PHGY 210 > Endo II > Flashcards

Endo II Flashcards

1
Q

Hormone secretion is controlled by […] feedbacks. Explain.

A

negative feedbacks.
An excess of hormone = diminution of hormone secretion
Deficiency of hormone = increase in hormone secretion

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2
Q

What are the two tissues that constitute the pituitary gland?

A

Anterior: endocrine tissue
Posterior: neuronal tissue - extension of hypothalamus

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3
Q

Name the two posterior pituitary hormones.

A

Arginine vasopressin and oxytocin

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4
Q

What is the function of arginine vasopressin?

A

It controls blood pressure

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5
Q

Compare the structures and functions of the two posterior pituitary hormones.

A

Arginine vasopressin and oxytocin have similar structures. Over time, they diverged into these two different hormones. Both of their functions involve control of smooth muscle tone, so although they function in different locations, they are alike.

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6
Q

Name the 6 hypophyseotrophic hormones.

A

TRH, GnRH, stomatostatin, GRH, dopamine, CRH

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7
Q

Which hypophyseotrophic hormone is not gene-encoded? What type of hormones are the rest of them?

A

Not gene encoded: dopamine
Others: peptides

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8
Q

Where is oxytocin secreted? Where is it synthesized?

A

It is secreted from the posterior pituitary gland. It is synthesized in the two hypothalamic nuclei: the supraoptic nucleus and the paraventricular nucleus.

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9
Q

Where is vasopressin secreted? Where is it synthesized

A

It is secreted from the posterior pituitary gland. it is synthesized in the two hypothalamic nuclei: the supraoptic nucleus and paraventricular nucleus

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10
Q

Describe the origin, destination, and route that oxytocin and vasopressin take to their destination.

A

Origin: the supraoptic nucleus and paraventricular nucleus in the hypothalamus.
Destination: the capillary blood vessels
Route: travel down the pituitary stalk, where they are processed as prohormones.

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11
Q

Oxytocin and vasopressin and processed as […] in secretory granules during axonal transport.

A

prohormones

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12
Q

The carrier molecules of mature oxytocin and vasopressin are called […]

A

neurophysins

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13
Q

What is the half life of vasopressin and oxytocin? Is this a long or short half life?

A

1-3 minutes. This is a short half life, especially given their long processing time.

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14
Q

Name the 3 main functions/effects of oxytocin in females.

A
  1. Parturition
  2. Milk ejection
  3. Behavioural effects
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15
Q

Explain how oxytocin’s effect on parturition in females.

A

The uterus expresses high levels of oxytocin receptors at the end of pregnancy. The dilation of the cervix by the fetal head causes the release of oxytocin, which causes uterine contraction. This assists in the expulsion of the fetus and placenta.

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16
Q

Explain oxytocin’s effect on milk ejection.

A

In a lactating mother, oxytocin causes milk-filled ducts to contract and squeeze milk out in response to suckling.

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17
Q

Explain oxytocin’s behavioural effect on females.

A

Local oxytocin release in the brain reduces anxiety and enhances bonding and pro-social behaviour (“love hormone”)

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18
Q

Name the 2 main effects of oxytocin in males.

A
  1. Ejaculation
  2. Behavioural effects
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19
Q

Explain how oxytocin affects ejaculation in males.

A

Oxytocin surges during sexual activity, which assists with the passage of sperm and ejaculation

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20
Q

Explain how oxytocin affects behaviour in males.

A

Local oxytocin release in the brain reduces anxiety and enhancing bonding and pro-social behaviour (“love hormone”)

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21
Q

Where is the thyroid gland located?

A

Right above the trachea.

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22
Q

The colloid component of the thyroid gland consists of […], which is a […]

A

Thyroglobulin, large protein

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23
Q

Thyroglobulin contains which thyroid hormones?

A

Thyroxine (T4) and triiodothyronine (T3)

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24
Q

What is the purpose of thyroglobulin?

A

It provides storage for T4 and T3 proteins prior to their release into the blood.

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25
Q

The synthesis of thyroglobulin is under control of […] secreted by the […]

A

TSH, pituitary gland

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26
Q

How much healthy thyroid is needed to maintain euthyroid state?

A

3 g

27
Q

How much healthy thyroid do individuals typically have?

A

15 to 20 g

28
Q

Thyroid hormones are notable for containing […]

A

iodine

29
Q

How does iodine enter the thyroid?

A

Thyroid follicular cells can trap iodide and transport it across the cell against its chemical gradient (active transport).

30
Q

What substance controls the steps of T4 and T3 formation? In what way?

A

The rate of all steps of T3 and T4 formation is increased by TSH.

31
Q

Describe the 3 steps of thyroid hormone synthesis and storage.

A
  1. Iodine (I2) is added to thyroglobulin residue to form MIT or DIT.
  2. Oxidative coupling of 2 DIT forms T4 and oxidative coupling of 1 MIT forms T3.
  3. T3 and T4 are stored linked to thyroglobulin.
32
Q

Draw and describe the feedback loop of thryoid hormone production.

A
  • Hypothalamic neurons: TRH
  • Anterior pituitary: TSH
  • Activates specific receptors on Thyroid gland
    • Increases cAMP
    • Increases adenylyl cyclase
  • Both increase T3 and T4
  • T3 and T4 decrease TRH and TSH
33
Q

In thyroid activity, the synthesis and release of TSH is controlled by […]

A

TRH (thyrotropin releasing hormone)

34
Q

When T4 and T3 increase in the blood, what is the effect on thyroid activity? Explain why.

A

When they increase, they exert a negative feedback at both the hypothalamic and pituitary levels to decrease release of TRH and TSH.

35
Q

What is the effect of iodide deficiency on the thyroid hormone synthesis feedback loop?

A

When iodide is deficient, synthesis of thyroid hormones decrease and T4 and T3 in circulation decrease.

  • Release of TSH increases and the thyroid follicular cells are constantly stimulated.
  • Thyroid enlarges and may form a visible lump, a goiter.
36
Q

What are the health effects of the enlarged thyroid caused by iodide deficiency?

A

There are none. The enlarged thyroid is simply unable to synthesize thyroid hormones despite being continually stimulated, so it is a non-toxic goiter.

37
Q

Name the 6 main effects of thyroid hormones. What is the most important effect?

A
  1. Stimulation of calorigenesis in most cells
  2. Increase oxygenation of blood
  3. Effects on carbohydrate metabolism
  4. Effects on lipid turnover
  5. Effects on protein metabolism
  6. Promote neural growth

The most important effect is the impact on growth during child development.

38
Q

How do the thyroid hormones affect basal metabolic rate?

A

T4 and T3 both increase basal metabolic rate and have major effects on metabolism of carbohydrates, lipids, and proteins. This increased metabolic activity also increases the need for oxygen.

39
Q

How do thyroid hormones affect the central nervous system? What happens if they are not present?

A
  • They are necessary for normal development, as they stimulate the synthesis of nerve growth factor (NGF), which allows for dendritogenesis and regeneration of sympathetic neurons.
  • Absence of thyroid hormones at early stages of development leads to irreversible metal retardation.
40
Q

Name the 3 molecular mechanisms of thyroid hormones.

A
  1. T3 and T4 enter the target cell nucleus and bind to their cognate nuclear receptor. This alters the transcription and translation of specific proteins.
  2. Thyroid hormones have interactions with the plasma membrane and mitochondria, which have a specific receptor for T4/T3.
  3. They act directly at the plasma membrane and increase the uptake of amino acids.
41
Q

How would the introduction of protein synthesis inhibitors affect the action of thyroid hormones?

A

It would prevent them from altering the transcription and translation of specific genes/proteins. However, this would not affect their interaction with the mitochondria or with the plasma membrane to increase amino acid uptake.

42
Q

The treatment for thyroid cancer is […]

A

radioactive iodine

43
Q

What is hypothyroidism?

A

Low levels of thyroid hormones due to hypofunction of the thyroid gland

44
Q

What is hyperthyroidism?

A

High levels of thyroid hormones due to hyperfunction of the thyroid gland

45
Q

Name some of the major effects of hyperthyroidism.

A
  • Elevated T3 and T4
  • Elevated BMR (hyopermetabolism)
  • Increased perspiration
  • Rapid pulse
  • Increase body temperature
  • Heat intolerance
  • Weight loss
  • Increased appetite
  • Goiter (in some individuals)
    Etc.
46
Q

Name some of the effects of hypothyroidism.

A
  • Decreased or absent T3 and T4
  • Low BMR (hypometabolism)
  • Decreased pespiration
  • Slow pulse
  • Lowered body temperature
  • Cold intolerance
  • Weight gain
  • Loss of hair
    Etc.
47
Q

What are the 3 possible causes of primary hypothyroidism?

A
  1. Idiopathic atrophy of thyroid
  2. Autoimmune thyroiditis aka Hasimoto’s disease (more common in women)
  3. Non-toxic goitre: blockage in step of T3/T4 synthesis. Leads to increased thyroid gland size and a non-toxic goitre forms
48
Q

What is myxedema?

A

Another title for primary hypothyroidism

49
Q

What is primary hypothyroidism and who is most affected by it?

A

Inability to synthesize active thyroid hormones at the level of the thyroid. It is more common in women than men, and appears at 40-60 years of age.

50
Q

Oxytocin and vasopressin and processed as prohormones in […] during axonal transport.

A

secretory granules

51
Q

What is secondary hypothyroidism?

A

At the level of the pituitary; synthesis of little or no TSH

52
Q

What is tertiary hypothyroidism?

A

At the level of the hypothalamus; synthesis of little or no TRH

53
Q

What is infantile hypothyroidism? What are the major effects of it on the individual?

A

Absence of thyroid gland or incomplete development of the thyroid gland at birth. At birth, the infant is normal because it uses mother’s T3/T4. But a few months later, the child exhibits decreased physical growth and mental development. Can lead to dwarfism and cretinism.

54
Q

What is the treatment for hypothyroidism?

A

All types of hypothyroidism are effectively treated by administration of thyroid hormones.

55
Q

What is an ectopic thyroid?

A

It is a thyroid that developed on the wrong side of the throat.

56
Q

What is primary hyperthyroidism? What forms can it take?

A

Primary hyperthyroidism occurs at the level of the thyroid gland. It can take the form of either Graves disease or thyroid adenoma/thyroid cancer

57
Q

Explain how Graves disease affects the functioning of the thyroid hormone feedback loop.

A
  • The disease causes the presence of LATS, which mimic the action of TSH and stimulate the release of T4 and T3.
  • This leads to constant stimulation, which increases the mass of the thyroid. This forms a toxic goitre.
    Note that the negative feedback loop of T3/T4 production still functions.
58
Q

Explain how thyroid adenoma works.

A

Synthesis of thyroid hormones independent of TSH stimulation.

59
Q

What is secondary hyperthyroidism? What is its cause?

A

Occurs at the level of the anterior pituitary gland. There is no negative feedback from increased levels of T3/T4 and synthesizes TSH autonomously. This is often due to the presence of a pituitary tumour.

60
Q

What is tertiary hyperthyroidism? What is its cause?

A

At the level of the hypothalamus. There is no negative feedback of high T3 and T4 to decrease synthesis of TRH. Often it is due to the presence of a hypothalamic tumour.

61
Q

What are the 3 typical treatments for hyperthyroidism?

A
  1. Surgery plus thyroid hormone adminstration
  2. Administration of radioactive iodide, which will concentrate in the cells of the thyroid follicles and destroy them. Replacement therapy may be administered.
  3. Administration of antithyroid drugs such as propylthiouracil, which blocks the addition of iodine to thyroglobulin.
62
Q

What is propylthiouracil? What is its function?

A

It is an antithyroid drug used to treat hyperthyroidism. It works by blocking the addition of iodine to thyroglobulin.

63
Q

What is Hashimoto’s disease?

A

It is a cause of primary hypothyroidism in which the immune system attacks the thyroid.

PHGY 210 (36 decks)

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