The Thyroid Gland Flashcards

1
Q

What does TH produce?

A

Thyroid Hormones (T3 and T4)

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2
Q

What cells do the thyroid gland contain?

A

C cells - secretes calcitonin

Follicular Cells - Support thyroid hormone synthesis and surround hollow follicles

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3
Q

What is thyroglobulin?

A

A large protein rich in tyrosine residues

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4
Q

Describe the link between iodide and follicular cells?

A

Follicular cells concentrate iodide cells from plasma and transport it to colloid where is combines with tyrosine to form thyroid hormones

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5
Q

How does iodide enter follicular cells?

A

Na+/I- transporter

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6
Q

How does iodide enter the colloid?

A

Via the pendrin transporter

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7
Q

How is iodide added on to tyrosine?

A

Enzymes are exocytosed into the colloid, alongside thyroglobulin. This catalises the reaction of the addition of iodide to tyrosine

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8
Q

What occurs when one iodine molecule to tyrosine?

A

Monoiodotyrosine is made

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9
Q

What occurs when two molecules of iodide are added to tyrosine?

A

Diiodotyrosine

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10
Q

What happens when MIT is added to DIT?

A

T3 is formed

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11
Q

What happens when two molecules of DIT are added together?

A

T4 is formed

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12
Q

How do cells respond to TSH?

A

Portions of the colloid are taken back up into the follicular cell by endocytosis. Within the cells, vesicles which contain proteolytic enzymes that cut the thyroglobulin to release thyroid hormones

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13
Q

Where do T3 and T4 circulate?

A

The plasma

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14
Q

To what does T3 and T4 bind to?

A

Thyroxine-binding Globulin

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15
Q

When is Thyroid Hormone release stimulated?

A

During exercise, pregnancy and when you’re cold

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16
Q

What inhibits TSH?

A

Somatostatin

17
Q

What inhibits TSH and conversion of T4 to T3?

A

Glucocorticoids

18
Q

What is T3?

A

The active form of thyroid hormone

19
Q

What is T4?

A

The plasma form of thyroid hormone

20
Q

What is the function of Thyroid Hormone?

A

They bind to nuclear receptors in the target cells and change transcription and translation to alter protein synthesis

21
Q

What affect does TH have on metabolic rate?

A

It increases it and promotes thermogenesis

22
Q

What affect does TH have on hepatic gluconeogenesis?

A

It increases it

23
Q

What affect does TH have proteolysis and lipolysis?

A

There is an net increase

24
Q

What does lack of TH result in?

A

Retarded growth

25
Q

What is congenital hypothyroidism caused by?

A

Dietary iodine deficiency in the mother

26
Q

What is graves disease?

A

An autoimmmune disease where antibodies produced bind and micmic TSH which continuously activates the thyroid gland. Increased release of TH switches off TSH release from ant. pituitary, Plasma [TSH] is very low.

27
Q

What is a thyroid adenoma?

A

Hormone secreting thyroid tumour

28
Q

Why are those with hyperthyroidism intolerant to heat and experience weight loss?

A

There is an increased metabolic rate and heat production

29
Q

Increased protein catabolism in hyperthyroidism causes what symptoms?

A

Muscle weakness/weight loss

30
Q

Why do hyperthyroidism patients have an altered nervous system function?

A

Hyperexcitable reflexes and physiological disturbances occur in hyperthyroidism

31
Q

What is the result of the elevated cardiovascular function seen in hyperthyroidism?

A

Increased HR/ Contractile Force, High output, cardiac failure

32
Q

What are some cause of Hypothyroidism?

A

Hashimoto’s Disease (Autoimmune attack on thyroid gland), Dietary iodine deficiency, Idiopathic

33
Q

What are the symptoms of hypothyroidism?

A

Weight gain/cold intolerance (Decreased metabolic rate and heat production), Brittle nails/Thin skin (disrupted protein synthesis), Slow speech/reflexes and fatigue (altered nervous system function), Slow heart rate and weaker pulse (reduced CVS function)