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Neuroendocrine > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

For the Thyroid hormone axis, what does the hypothalamus release?

A

TRH

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2
Q

For the Thyroid hormone axis, what does the anterior pituitary release?

A

TSH

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3
Q

What are the 2 types of thyroid hormones?

A

T3 and T4

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4
Q

What thyroid hormone is the active form?

A

T3

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5
Q

What is the main thyroid hormone secreted?

A

T4

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6
Q

What must 80-90% of T4 undergo in order to create T3?

A

Peripheral conversion

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7
Q

For peripheral conversion, what takes T4 to T3’s active form?

A

Deiodinase type 1 and 2

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8
Q

For peripheral conversion, what takes T4 to T3’s inactive form?

A

Deiodinase type 3

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9
Q

What can inhibit peripheral conversion of T4 to T3?

A

Fasting, medical stress, catabolic diseases

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10
Q

How does Iodide, get into the follicular cell of the thyroid from the blood?

A

Iodide trap - comes into the cell with sodium

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11
Q

What pump takes Iodide from the follicular cell into the colloid?

A

Pendrin

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12
Q

Once in the colloid, what enzyme takes Iodide to Iodine and attaches to tyrosine residues within Thyroglobulin, as well as coupling?

A

Thyroid Peroxidase (TPO)

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13
Q

What is the storage from of T3 and T4?

A

Attached to Thyroglobulin tyrosine residues in colloid

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14
Q

Once TSH stimulates thyroid gland, how does it release T3 and T4?

A

Endocytosis

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15
Q

T3 and T4 are normally bound to what protein in the blood?

A

Thyroxine Binding Globulin (TBG)

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16
Q

Thyroxine Binding Globulin (TBG) has a higher affinity for which thyroid hormone?

A

T4

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17
Q

DIT

A

1 tyrosine residue plus 2 iodines

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18
Q

MIT

A

1 tyrosine residue plus 1 iodine

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19
Q

How do you make T4?

A

DIT + DIT

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20
Q

How do you make T3?

A

DIT + MIT

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21
Q

What is the result of a mutation in pendrin?

A

Sensorineural hearing loss, goiter, hypothyroidism

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22
Q

High levels of iodide that inhibit the synthesis of T3 and T4

A

Wolff-Chaikoff Effect

23
Q

Effective treatment for hyperthyroidism?

A

PTU

24
Q

How do you measure the activity of the thyroid gland?

A

Measuring radioactive iodine uptake

25
Q

Steady increase of radioactive iodine uptake

A

Hyperthyroidism

26
Q

Extremely fast increase of radioactive iodine uptake that starts to decrease after 24 hours due to high turnover

A

Grave’s Disease

27
Q

TBG has a higher affinity for T4, what does this do to the half life of T4?

A

Increases it compared to the half life of T3

28
Q

How do you measure circulating levels of TBG?

A

T3 resin uptake

29
Q

High TBG means?

A

Increased T4 and decreased T3 resin uptake

30
Q

Low TBG means?

A

Decreased T4 and increased T3 resin uptake

31
Q

Hepatic failure does what to levels of TBG?

A

Decreases

32
Q

Pregnancy can do what to level of TBG?

A

Increase

33
Q

Describe the results of pregnancy increasing TBG

A

This decreases free T3 and T4 because there will be more bound to TBG. There will be a transient increase in secretion of T3 and T4, but free levels will remain normal due to higher binding proteins =
clinically euthyroid

34
Q

Summarize the synthesis of T3 and T4

A
  • Iodide transported into the follicular cell from the blood due to iodide trap with sodium
  • Pendrin transports Iodide into colloid
  • Thyroid Peroxidase converts it to Iodine, attaches them to tyrosine residues of Thyroglublin and couples DITs/MITs
  • When TSH stimulates, endocytosis will occur to release T3 and T4 from thyroglobulin so they can bind TBG in the blood stream
35
Q

List 3 proteins that are synthesized under direction of thyroid hormones

A
  1. Na+/K+ ATPase
  2. Beta1 adrenergic receptors in cardiac cells
  3. Metabolic enzymes in liver/adipose tissue
36
Q

What is the effect of thyroid hormones on cardiac cells?

A

Increases the number of beta1 adrenergic receptors which INCREASES the total cardiac output!!

37
Q

What is the effect of thyroid hormones stimulating more Na+/K+ ATPase?

A

Increased basal metabolic rate (BMR)

38
Q

Increased BMR

A

Hyperthyroidism

39
Q

Decreased BMR

A

Hypothyroidism

40
Q

Hypothyroidism does what to cholesterol?

A

Increases it

41
Q

General symptoms of hyperthryoidism

A

Increased BMR, weight loss, sweating, increased HR, exopthalmos

42
Q

General symptoms of hypothyroidism

A

Decreased BMR, weight gain, lethargy, coldness

43
Q

Thyroid hormones are essential for ____ maturation

A

CNS

44
Q

Thyroid hormones work with what to stimulate bone formation?

A

GH

45
Q

Another name for hyperthyroidism

A

Thyrotoxicosis

46
Q

Describe Grave’s disease

A

Antibodies stimulate TSH receptor that causes an overproduction of T3 and T4

  • levels of TSH are low due to negative feedback from high levels of T3 and T4
  • Presence of TSI - Thyroid stimulating immunoglobulins
47
Q

TSH-secreting pituitary

A

Secondary hyperthyroidism

48
Q

Most common cause of hypothyroidism in iodine-sufficient areas of the world

A

Hashimoto’s thyroiditis

49
Q

Describe Hashimoto’s Thyroiditis

A

Antibodies to Thyroglobulin or Thyroid Peroxidase (TPO) which impairs thyroid hormone synthesis even if TSH levels are HIGH

50
Q

What can cause congenital hypothyroidism?

A

Iodide deficiency, maternal intake of anti-thyroid meds

51
Q

Signs of hypothyroidism in babies?

A

Feeding problems, protruding tongue, retardation, breathing problems

52
Q

Sheehan syndrome

A

Necrosis of pituitary gland postpartum - causes difficulty with lactation and may impair other endocrine glands

53
Q

Can you have a goiter with hyperthyroidism and hypothyroidism?

A

Yes

Neuroendocrine (47 decks)

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