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Endocrine & Reproductive Systems > Drugs control of thyroid, adrenal and GH secretion > Flashcards

Drugs control of thyroid, adrenal and GH secretion Flashcards

0
Q

What is the difference between T3 and T4?

A
  • T3 is the active hormone which exerts effects on cells ; T4 has to be deiodinated to form T3
  • T4 itself is inactive
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1
Q

What is the structural unit of the thyroid?

A
  • follicles
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2
Q

How is thyroid hormone synthesised and secreted?

A

1- uptake of iodide by Na/I transporter
2- thyroperoxidase oxidises iodine into iodide + iodinate thyroglobulins at the follicle lumen
3- the iodinated thyroglobulin molecules then form a vesicle and return back into cells
4- lysosomes break the vesicle = T3+ T4 are released

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3
Q

What can increase thyroid hormone release?

A
  • cold, trauma and stress
    = increase in TRH, TSH and in turn stimulates the thyroid follicle cells to produce T3 and T4
    = by increasing occurrence of iodination and increase amount of thyroglobulin proteins
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4
Q

What are the actions of thyroid hormone?

A
  • increase calorigenesis, metabolism
  • exerts CVS effects (increase heart rate)
  • growth and maturation
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5
Q

How can TSH up regulate thyroid gland functions? ie via what mechanisms?

A
  • by increasing expression level of NA/I carrier= increase uptake of iodide, iodination and coupling of thyroglobulin proteins
  • increase secretion of T3/T4 out of vesicles
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6
Q

What is the mechanism of action of T3/T4?

A
  • exerts effects by binding to nuclear receptors of cells
  • have direct effects on regulation of genes, ie increase gene transcription
  • There is a higher conc of T4 in blood than T3 because T3 is more potent so need fewer of them to circulate in blood to exert effects
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7
Q

What are the causes of hypothyroidism? (4)

A
  • iodine deficiency in diets
  • natural goitrogens which interferes with iodine uptake
  • autoimmune thyroiditis where antibodies are produced against the thyroglobulin proteins so no T3/T4 can be made
  • atrophy of thyroid = thyroid gland is destructed
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8
Q

How do you classify hypothyroidism?

A
  • primary: at the level affecting the thyroid gland
  • secondary: at the level affecting anterior pituitary gland
  • tertiary: at the level affecting hypothalamus
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9
Q

What are the symptoms hypothyroidism?

A
  • cretinism in young; myxoedema in adults

* myxoedema= cold intolerant, lethargy, weigh gain, husky voice, muscle weakness

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10
Q

How do we diagnose hypothyroidism? (4)

A
  • increased levels of TSH
  • thyroglobulin antibodies found (in autoimmune thyroiditis)
  • decreased levels of T4
  • hypercholesterolaemia
  • high level of cholesterol because thyroid hormones normally increases level of expression of LDL receptors. Fewer thyroid hormones= fewer LDL receptors so fewer LDL can be taken into cells
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11
Q

What is the treatment of hypothyroidism?

A
  • always REPLACEMENT

eg levothroxine sodium, T4 ( orally, standard treatment)
tri-iodothyronine, liothyonine, T3
-> these are for hypothyroidism that is NOT caused by iodide deficiency

eg sodium iodide or potassium iodide
-> these are hypothyroidism that is caused by iodide deficiency

  • main treatment is T4 as they last for longer due to have to be deiodinate; T3 is only used in emergency because it can create an immediate acute response on CVS and other side effects
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12
Q

What are the symptoms of hyperthyroidism?

A
  • irritability, heart racing, hand tremors, difficulty sleeping, fine brittle hair, muscular weakness
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13
Q

What are the most common cause of hyperthyroidism? (2)

A
  • Grave’s disease: antibodies formed binds to TSH receptors and increases production of T3 and T4
  • tumours of thyroid glands
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14
Q

How do you diagnose hyperthyroidism? (4)

A
  • symptoms of hyperthyroidism
  • mass at base of the neck (tumour/ goitre)
  • increased level of T4/T3
  • decrease level of TSH ( due to negative feedback from T3/T4)
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15
Q

What are the treatments for hyperthyroidism? (5)

A
  • drugs that inhibit T3/T4 secretion
  • high doses of iodide
  • thyroidectomy
  • beta-adrenergic receptor antagonist
  • Radial iodine
16
Q

What drugs are used to inhibit secretion of T3/T4?

A
  • thiureylenes; carbimazole; methimazole; felimazole
  • side effects = hypothyroidism, but they are rare; reduce in level of platelets and white cells due to reduction in granulocytes

** usually take one month to work even though the drugs inhibit the enzymes efficiently, due to there is a reservoir of T3/T4

17
Q

How do high doses of iodide inhibit thyroid hormone synthesis?

A
  • mechanism unclear but can reduce level of thyroid efficiently for 3 months then the system becomes desensitised to high level of iodide so no longer works
18
Q

How does thyroidectomy treat hyperthyroidism?

A
  • removal of thyroid gland then will indue hypothyroidism
19
Q

How do beta-adrenergic receptor antagonists work in treating hyperthyroidism?

A
  • does not treat hyperthyroidism but reduce the CVS effects caused by high thyroid level
    eg propranolol
20
Q

How do radial iodine work in treating hyperthyroidism?

A
  • localised radioactivity (only very limited distance it can travel) in destroying some follicle cells = very effective
  • takes time to work
21
Q

How are mineralocorticoids and glucocorticoids produced in adrenal glands?

A
  • hypothalamus release CRF which acts on anterior pituitary to produce ACTH
  • ACTH acts on adrenal cortex to produce mineralocorticoids and glucocorticoids
22
Q

What can be given to replace ACTH if it is not being produced efficiently in anterior pituitary?

A
  • ACTH or tetracosactide ( ACTH analogue)
23
Q

What are the components of glucocorticoids?

A
  • hydrocortisone and corticosterone
  • hydrocortisone= convert fats and proteins into energy and helps to regulate CVS
  • corticosterone= works with hydrocortisone and regulates inflammatory response
24
Q

In Cushing’s disease, what do you give to patients?

A
  • Cushing’s= too much adrenal activity so producing excess glucocorticoids
25
Q

What do you use to test the function of anterior pituitary and hypothalamus?

A
  • metyrapone
26
Q

What is Cushing’s disease?

A
  • when there is an excess of hydrocortisone
27
Q

What do you give patients who have Addison’s disease?

A
  • hydrocortisone and fludrocortisone
28
Q

What is Addison’s disease?

A
  • when there is a glucocorticoids deficiency
29
Q

What do you use to diagnose GH deficiency? (Ie anterior pituitary malfunction)

A
  • sermorelin (a GHRF analogue)
30
Q

What can cause a reduction of GH production?

A
  • somatostatin
31
Q

What drugs stimulate somatostatin receptors in anterior pituitary to reduce GH release?

A
  • octreotide and lanreotide
32
Q

What is the drug used for replacement therapy in GH deficiency?

A
  • Somatotropin

Endocrine & Reproductive Systems (11 decks)

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