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PM3B: Autumn > Thyroid Systems > Flashcards

Thyroid Systems Flashcards

1
Q

Explain the hypothalamic regulation of thyroid function?

A
  1. Hypothalamus contains parvocellular neurosecretory cells that release Thyrotropin Releasing Hormones (TRH)
  2. Inflow of blood from superior hypophyseal artery carries hormones across to anterior pituritary
  3. The endocrine then releases to the vein Thyroid Stimulating Hormone- Thyrotropin (TSH)
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2
Q

What effect does the thyroid hormones have on basal metabolic rate

A

Raised O2 consumption

Raised CO2 and heat production

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3
Q

What effect does the thyroid hormones have on cardiovascular system

A

Increases heart rate and force of contraction

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4
Q

What effect does the thyroid hormones have on nervous system

A

Increases activity of sympathetic nervous system

Enhances the sensitivity to catecholamines

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5
Q

What effect does the thyroid hormones have on growth and maturation

A

Embryo development

CNS development

Linear growth (promotes growth hormone effect)

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6
Q

What role does C cells play in thyroid follices

A

Make calcitonin, lowers calcium levels by inhibiting bone breakdown- involved in managing calcium balance

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7
Q

How do you form the two types of iodinated molecules?

A

Combination of Thyroglobulin (contains high amount of tyrosine) with Iodine (I2) made form iodide (I-) taken up from the blood

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8
Q

What are the two couple of iodinated molecules called

A

MIT: mono-iodotyrosine- one iodine per tyrosine

DIT: di-iodotyrosine- two iodines per tyrosine

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9
Q

How do you produce Thyroxine (T4)

A

DIT (di-iodotyrosine) + DIT

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10
Q

How do you produce Triiodothyronine (T3)

A

MIT (mono-iodotyrosine) + MIT

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11
Q

Explain how the Thyroid hormones are released

A
  1. Follicular cells take up portion of colloid in lumen (endocytosis)
  2. Lysosomal enzymes in follicular cell break down the iodinated thyroglobulin, this creates T3 and T4
  3. T3 and T4 diffuse via the plasma membrane of the follicular cell into the blood
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12
Q

What is the role of TBG (thyroxine binding globulin)

A

Releases bound T3 and T4 to exert its biological effect

Needed to circulate blood stream as we know T3 and T4 have poor solubility in water

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13
Q

Which is more active between T3 and T4, explain

A

T3 is more active as it binds to the thyroid hormone with a higher affinity than T4

Local tissues convert T4 into T3 via removal of one iodine

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14
Q

Explain how thyroid hormones are transported around the body to have its targeted effect

A
  1. They are lipophilic in nature and are transported in blood stream bound to carrier protein (TBG and albumin)
  2. The activated receptor hormone complex can alter the gene expression
  3. Newly formed mRNA directs specific synthesis of specific proteins on ribosomes which bind to intracellular receptors on target cell
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15
Q

What are the three diseases associated with the thyroid hormone

A

Goitre

Cretinism

Grave’s disease

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16
Q

Describe what goitre is

A

Hypertrophy of thyroid gland (too much TSH stimulation)

Associated with hypo/hyperthyroidism forms

Association with autoimmune disease

17
Q

What can hypothyroidism lead to symptom wise

A 
Weight gain
Cold intolerance 
Lethargy and depression
Puffiness of skin and muscles
Muscular weakness
Sluggish Reflexes
Reduced pulse and cardiac output
18
Q

Describe what cretinism is

A

Hypothyroidism in kid that can cause fetal brain damage
Shortness
Obesity
Mental retardation

19
Q

How do you treat hypothyroidism

A

Life long replacement with T4

Levothyroxine- identical to natural T4

20
Q

What is the drug that is identical to T3 and T4 called

A

Liothyroxine- T3

Levothyroxine- T4

21
Q

What is Hashimoto’s thyroiditis

A

An autoimmune disease that causes damage to the gland which can lead to hypothyroidism

22
Q

What are the symptoms of hyperthyroidism

A 
Weight loss
Nervousness
High cardiac output
Heat intolerance
Hand tremor 
eyeball protrusions
23
Q

What is Grave’s disease

A

Cause of hyperthyroidism
Peculiar form of autoimmune disease
Reason: Thyroid stimulating antibody that mimics TSH
HIGH T3/T4, LOW TSH, goitre

24
Q

How do you treat hyperthyroidism

A

Interfere with thyroid synthesis by blocking the thyroid peroxidase enzyme (prevents iodination of thyroglobulin)

Drug: CARBIMAZOLE

PM3B: Autumn (19 decks)

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