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SUGER > Thyroid And Parathyroid Physiology > Flashcards

Thyroid And Parathyroid Physiology Flashcards

1
Q

Where is the thyroid gland located

A

It is located in the anterior of the neck just below the larynx

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2
Q

What makes up the thyroid

A

The thyroid is made up by right and left lobes which are joined in the middle by an isthmus

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3
Q

What is the thyroid made up

A

Thin fibrous capsule of connective tissue

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4
Q

What is found in the middle of the thyroid follicles

A

Colloid

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5
Q

What can be found surrounding follicular cells

A

C-cells

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6
Q

What do thyroid hormones control

A

Control of metabolism : energy generation and use

Regulation of growth

Roles in development

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7
Q

Explain how thyroid hormone secretion is regulated

A

The hypothalamus is stimulated to release thyroid releasing hormone which travels to the anterior pituitary to stimulate the release of thyroid secreting hormone. This stimulates the thyroid to produce thyroid hormones T3 and T4. T4 has a negative feedback affect on the hypothalamus and the pituitary to stop it releasing TRH and TSH. T4 binds to T3 to enter target cells. When T3 enters target cells it has a negative feedback affect and tells the hypothalamus and pituitary to stop producing TRH and TSH

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8
Q

Explain the process of thyroid hormone synthesis

A

6 steps

1 - active transport of iodide into follicular cell via sodium-iodide symporter

2 - thyroglobulin is formed in the follicular ribosome

3 - exocytosis of thyroglobulin into the follicle lumen where it is stored as colloid

4 - iodination of the thyroglobulin, iodide is made reactive by thyroid peroxidase, iodide binds and forms MIT and DIT

5 - Coupling of MIT and DIT = T3 and Coupling of DIT and DIT = T4

6 - endocytosis of iodinated thyroglobulin goes back into the follicular cell and undergoes proteolysis to cleave tyrosine, free T3 and T4 is released

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9
Q

Which thyroid hormone is biologically active

A

T3 is biologically active thyroid hormone

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10
Q

What is thyroglobulin

A

Thyroglobulin is a large protein which is rich in tyrosine

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11
Q

If a patient is suspected to have hyperthyroidism what would there thyroid function tests

A

Low serum thyroid synthesising hormone
High serum T3
High serum T4

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12
Q

If a patient is suspected to have hypothyroidism what would there thyroid function tests

A

High serum Thyroid secreting hormone
Low serum T4
Low serum T3

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13
Q

Signs and symptoms of hyperthyroidism

A

Tachycardia
AF
Shortness of breath
Tremor
Anxiety
Weight loss
Increased appetite
Double vision

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14
Q

Symptoms of hypothyroidism

A

Bradycardia
Heart failure
Weight gain
Constipation
Vitiligo
Depression
Carpal tunnel syndrome

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15
Q

What is the role of the parathyroid gland

A

Regulate calcium and phosphate levels
Secreting parathyroid hormone in response to low calcium and high phosphate

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16
Q

What is the action of parathyroid hormone

A

Increase calcium reabsorption in renal distal tubule
Increase intestinal calcium absorption via activation of vit D
Increases calcium release from bone stimulates osteoclast activity
Decrease phosphate reabsorption

17
Q

What are the 2 types of cells in the parathyroid gland

A

Chief cells
Oxyphil cells

18
Q

What cells secrete parathyroid hormone

A

Chief cells

19
Q

What is calcium homeostasis

A

Regulates calcium flow to and from the bones

20
Q

What can inadequate calcium levels result in

A

Osteoporosis

21
Q

What is vitamin d converted to

A

Calcidiol

22
Q

Where is vitamin d converted

A

The liver

23
Q

What does calcitriol regulate

A

It regulates the levels of calcium and phosphorus in the blood and helps maintain healthy skeletal system

24
Q

How is bone resorption done

A

Done by osteoclasts

25
Q

What does calcitonin stimulate

A

The incorporation of calcium in bone

26
Q

Explain the process of vitamin D and calcium homeostasis

A

Vit D is converted to calcidiol in the liver, part of this is converted by the kidneys to calcitriol which is the biologically active of vit D.
Calcitriol circulates as a hormone in the blood which regulates the concentration of calcium and phosphate in the bloodstream and promoting healthy growth and remodelling of bone

27
Q

What is involved in the endocrine control of extracellular calcium homeostasis

A

Parathyroid hormone
Vitamin D
Calcitonin

28
Q

What makes parathyroid hormone

A

84 amino acids
But is biological activity in first 34 amino acids

29
Q

What is the half-life of parathyroid hormone

A

8 mins

30
Q

What does parathyroid hormone stimulate in the kidneys

A

Increases distal tubular reabsorption of calcium and inhibits phosphate reabsorption and stimulates the production of the active form of vit D

Enhances bone reabsorption by stimulating osteoclasts

31
Q

What inhibits the translation of parathyroid hormone

A

Increase of serum calcium

SUGER (17 decks)

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