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PMCOL 200 > Thyroid Pharmacology > Flashcards

Thyroid Pharmacology Flashcards

1
Q

What are the two classes of hormones released from the thyroid?

A

T3 (triiodothyronine) and T4 (thyroxine)

Calcitonin

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2
Q

How are thyroid hormones regulated?

A
  1. TRH is released from hypothalamus.
  2. TSH is stimulated by TRH and released from anterior pituitary.
  3. T3 and T4 exert negative feedback on TSH/TRH
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3
Q

What are the main physiological effects of thyroid hormones?

A
  1. Increased basal metabolic rate.
  2. Sensitization to catecholamines.
  3. Growth and development.
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4
Q

What is the precursor protein for thyroid hormones?

A

Thyroglobulin.

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5
Q

What amino acid does thyroglobulin contain?

A

Tyrosine.

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6
Q

How many iodine can be added to each tyrosine ring?

A

1: Monoiodine (MIT)

2. Diiodine (DIT)

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7
Q

Which thyroid hormones are composed from MIT/DIT?

A

2 DIT: T4

1 DIT/1 MIT: T3

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8
Q

What is the predominant thyroid hormone that is released?

A

Thyroxine (T4)

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9
Q

What hormone causes coupled MIT/DIT to be endocytosed and processed?

A

TSH.

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10
Q

What occurs in the apical portion of the thyroid follicle?

A

Iodination and coupling of thyroglobulin.

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11
Q

What occurs in the intracellular portion of the thyroid follicle?

A

Processing of thyroglobulin after being iodinated and couple (colloid), endocytosis.

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12
Q

What happens in the basolateral side of the thyroid follicle?

A

Release of T3/T4 into bloodstream.

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13
Q

How does the thyroid gland accumulate iodide from the bloodstream?

A

Na/I co-transporter (symport)

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14
Q

What is the mechanism of action of thyroid hormones?

A

T3 is taken up by transmembrane receptors and bind to receptors in the nucleus. This causes the recruitment of RXR, which forms a heterodimer with the hormone receptor. This complex recruits co-activators that enhance transcription of target genes.

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15
Q

What is occurring in thyroid hormone target cells at rest?

A

Unbound thyroid hormone receptors associate with TRE to recruit co-repressors (weaken gene transcription)

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16
Q

What is hypothyroidism?

A

Deficient thyroid function.

17
Q

What is the cause of hypothyroidism?

A

Iodine deficiency
Hashimoto’s thyroiditis
Defects
Inappropriate hormonal regulation

18
Q

What is primary hypothyroidism?

A

Defect in the thyroid function; low T4/T3 but high TSH.

19
Q

What is secondary hypothyroidism?

A

Central defect (pituitary or hypothalamus); low T4/T3 low TSH

20
Q

What is the treatment for hypothyroidism?

A

Synthetic thyroxine (levothyroxine)

21
Q

What is hyperthyroidism?

A

Overactive thyroid function.

22
Q

What are the most common causes of hyperthyroidism?

A

Grave’s disease

Hyperplasia of thyroid (excess release)

23
Q

What is Grave’s disease?

A

Stimulation of thyroid by anti-TSH receptor antibodies; high T3/T4 and low TSH. Characterized by goiters and bulging eyes.

24
Q

What is thyroid hyperplasia?

A

Thyroid adenoma/goiter; high T4/T3 which causes negative feedback on TSH.

25
Q

What is secondary hyperthyroidism?

A

Central defect causing excess production of TSH; high T3/T4 high TSH

26
Q

What is the difference between Graves disease and Hashimotos?

A

Both are autoimmune disorders, but there are many lymphocytes and shriveled follicles present in the thyroid of Hashimotos disease (because of thyroid-specific cell attack)

27
Q

What causes goiters?

A

Overactivation of thyroid tissue leading to accumulation of thyroxine, or iodine deficiency which causes increased TSH.

28
Q

What is treatment for hyperthyroidism?

A
  1. Surgery and treatment with thyroxine, may cause parathyroid disturbances.
  2. Radioactive iodine treatment (destroys thyroid, but may cause destruction of baby’s thryoid in pregnant or breastfeeding women)
  3. Anti-thyroid drugs (methimazole) that prevent T3/T4 synthesis.
  4. Beta-blockers to treat tachycardia.
29
Q

What are thioamides?

A

Prevent iodination and coupling mediated by thyroperoxidase enzyme.

PMCOL 200 (19 decks)

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