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PharmacologyII > M2- lecture 15: thyroid disorders > Flashcards

M2- lecture 15: thyroid disorders Flashcards

1
Q

what hormones do the thyroid gland secrete?

A

thyroxine (t4)

tri-iodothyronine (t3)

calcitonin

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2
Q

what are t4 and t3 important for?

A

they are important for normal growth/ development and the control of energy metabolism.

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3
Q

whats the main steps in synthesis and storage of thyroid hormones ?

A

uptake of plasma iodide by the follicle cells

iodination of thyroglobulin

secretion of thyroid hormones

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4
Q

whats thyroperoxidase ?

A

it oxidizes iodine and incorporates iodine radicals into tyrosine residues of thyroglobulin

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5
Q

how are thyroid hormones regulates?

A

they are regulated by TRH and protirelin which causes the anterior pituitary to release TSH.

not the difference between TRH and TSH

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6
Q

what does TSH act on ?

A

acts on GPCR in thyroid follicle cells which increases cAMP and activates of PI3K.

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7
Q

what are the actions of TSH on thyroid cells and what type of actions are they?

A

TROPHIC ACTIONS

  • increases NIS expression
  • synthesis/secretion of thyroglobulin TG
  • generation of H2O2 and iodination of tyrosine
  • endocytosis/ proteolysis of TG
  • secretion of t3 and t4
  • increased blood flow through the gland.
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8
Q

what are the causes of hypothyroidism ?

A
  • hashimoto’s disease (autoimmune disorder)

- leads to enlargement of the thyroid gland (goitre)

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9
Q

what are the symptoms of hypothyroidism?

A
  • low metabolic rate, lethargy
  • slow speech
  • bradycardia
  • sensitivity to cold
  • myxedema (Severe cases)
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10
Q

what are some thyroid replacements for hypothyroidism?

A

T4 (most common)

t3 (more active)

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11
Q

whats the mechanism of action for thyroid replacements? the general mechanism of action.

A
  • exogenously administered t4 is deiodinated to t3

- bind to intracellular nuclear thyroid hormone receptors (10x more affinity for t3 than t4).

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12
Q

whats the MOA related to T3? for hypothyroidism ?

A

t3 impacts numerous bodily systems:
- metabolism: increased body temp and reduced weight

  • cardiovascular: increased HR and BP
  • GI: increased motility.
  • Musculoskeletal: required for skeletal development and peak bone mass.
  • reproductive: enhance ovulation and spermatogenesis
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13
Q

what are 2 adverse effects for hypothyroidism?

A

tachycardia (contraindicated)

atrial fibrillation

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14
Q

what are some causes of hyperthyroidism? (thyrotoxicosis)

A
  • diffuse toxic goitre (Graves’ Disease)

- toxic nodular goitre

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15
Q

what are some symptoms of hyperthyroidism?

A
  • high basal metabolism (increased appetite associated with body weight loss)
  • increased skin temp
  • heat intolerance
  • sweating
  • nervousness and tremor
  • tachycardia
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16
Q

when is surgery administered for hyperthyroidism?

A

used if mechanical problems occur like thyroid compressing the trachea.

17
Q

whats one drug thats used to treat hyperthyroidism ?

A

radioiodine (131I)

  • first line treatment for hyperthyroidism
  • dose is generally 5-15 mCi
18
Q

whats the MOA of radioiodine?

A
  • its taken up and processed the same way as normal iodine by the thyroid
  • isotope emits beta-particles that have a short range and cytotoxic actions within thyroid follicle cells.
  • given as a single dose that makes at least 1 month to start mediating its actions.
19
Q

what happens after radioiodine is administered?

A
  • following use and destruction of the gland, individuals will become hypothyroid and require administration of T4
20
Q

whats another drug thats used for hyperthyroidism?

A

Antithyroids (thioamides)

  • propylthiouracil
  • methimazole, carbimaxole (prodrug converted to methimazole)
21
Q

whats the MOA of antithyroids (thioamide)?

A

contain a thiocarbamide (S-C-N) group required for antithyroid activity

  • prevent synthesis of thyroid hormone
  • inhibit thyroperoxidase
  • block iodine oxidation
  • block coupling of iodinated tyrosines
  • inhibit peripheral deiodination of t4 to t3 (propylthiouracil)
  • REQUIRES 3-4 WEEKS TO WORK
22
Q

whats the contraindications for thioamides?

A

pregnancy

23
Q

what are some AE of thioamides?

A

skin rash,
neutropenia
-agranulocytosis

24
Q

what is antithyroid (Lugol Iodine)?

A
  • solution of potassium iodide with iodine in water
  • symptoms of thyrotoxicosis subside within 1-2 days
  • used for either severe thyrotoxicosis or preparation for surgery .
25
Q

whats the MOA of lugol iodine? (antithyroids)

A
  • iodide in excess amounts inhibits thyroid hormone secretion
  • reduces vascularity of the thyroid gland
  • may also inhibit iodination of thyroglobulin by reducing generation of H202.

PharmacologyII (12 decks)

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