Thyroid meds Flashcards by tcarlso 3

What are the two thyroid hormones? What is the difference between the two?

T3 and T4

T3 have three iodines, T4 has four

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What are the four general function of thyroid hormones?

growth
Development
Body temp
Energy metabolism

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How are thyroid hormones taken up by thyroid follicles?

Na/I symporter

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What causes the change from iodide to iodine?

Thyroid peroxidase

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What do the thyroid follicles surround?

Follicle lumen (colloid)

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What is organification of iodide?

Iodination of tyrosine residues within the thyroglobulin molecule

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What are the amino acids that comprise thyroglobulin?

Tyrosine

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What are the molecules that are combined to form thyroid hormones?

MIT and DITs

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What is the ratio of T4:T3?

5:1

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What does the thyroid follicle take up from the follicular space? How? What does this do?

Thyroglobulin
Phagocytosis
Degradation to T4

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What molecule does T3/4 bind to in the blood?

Thyroxine binding globulin

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Where is the T3 receptor found? What does it do there?

T3 receptor sits on the DNA on thyroid response element (TRE)

Represses gene expression

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What happens to T4 when endocytosed into the cell?

Changed to T3 by 5’-deiodinase

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Which form of thyroid hormone is the active one? Which is found in the highest amounts in the blood?

T3 is active form

T4 is highest in the blood

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Describe the HPA axis in regards to the thyroid expression

TRH expressed by the hypothalamus, promotes TSH release by pituitary. This causes the release of thyroid hormone from the thyroid, which will feed back to the hypothalamus to inhibit further secretion

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What is the effect of high iodide concentration?

Negative feedback on the thyroid

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What is the effect of Low iodide concentration?

Promotes hormone synthesis

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What are the two effects of the thyroid hormone on the sympathetic nervous system?

Increase beta adrenergic receptors

2. Decrease alpha adrenergic receptors

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What are the effects of the thyroid hormone on: growth and development?

Brain development and neurogenesis

2. Bone growth and skeletal maturation

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What are the effects of the thyroid hormone on: thermogenesis?

Increases cellular engery consumption

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What are the effects of the thyroid hormone on: Respiratory?

Increase O2 consumption, causing increase RR

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What are the effects of the thyroid hormone on: CNS?

Rapidity of cerebration

2. Effect spinal cord synapses that control muscle tone

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What are the effects of the thyroid hormone on: the GI tract?

Increase secretions and motility

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What are the effects of the thyroid hormone on: skin and hair?

!. trophic effect

2. Prevent accumulation of glycosaminoglycans (causes water retention)

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What are the effects of the thyroid hormone on: the CV system?

1. Increase HR 2. Increase contraction 3. Increase CO 4. Increased BP 5. Decrease resistance

What are the effects of the thyroid hormone on: metabolism

Increase BMP Increased protein synthesis Decreased Fat level

Atherosclerosis is seen in hypo or hyperthyroidism

Hypo

Cold intolerance is seen in hypo or hyperthyroidism

Hypo

Low respiratory rate is seen in hypo or hyperthyroidism

Hypo

Diarrhea is seen in hypo or hyperthyroidism

Hyper

Dry and scaly skin, depressed hair and nail growth is seen in hypo or hyperthyroidism

Hypo

Fluid retention is seen in hypo or hyperthyroidism

Hypo

MR is seen in hypo or hyperthyroidism

Hypo

Vitamin deficiency is seen in hypo or hyperthyroidism

Hyper

Decrease in strength is seen in hypo or hyperthyroidism? Why?

Hyper, due to increased catabolism

What causes the increased fluid retention in hypothyroidism?

Accumulation of GAGs in interstitial space d/t decreased clearance

What is myxedema, and what is it seen in?

Swelling around the eyes in hypothyroidism d/t GAG accumulation

What is Cretinism?

Hypothyroidism d/tt lack of thyroid development of TSH receptor responsiveness

What is hashimoto's thyroiditis? Is this hyper or hypothyroidism?

Infiltration of lymphocytes in the thyroid gland, causing destruction of the thyroid Initially hyper when thyroid hormone stores released, then hypo when depleted

What medication cause destroy the thyroid?

What are the causes of secondary hypothyroidism?

``` Head trauma Cranial neoplasm Brain infx Cranial irradiation Neurosurgery ```

What are the three synthetic thyroid hormones?

Levothyroxin Liothyronine Liotrix

What is levothyroxine?

Synthetic T4

What is Liothyronine?

Synthetic T3

What is Liotrix?

Synthetic mix of T3 and T4

Why is Levothyroxine given more often than Liothyronine?

Since T4 is more common in the blood, closer to physiologic concentrations

What is the complication of treating elderly pts with hypothyroidism and CAD?

Hypothyroidism is protective against CV problems, so "curing" hypothyroidism may cause increased in CV problems

What is the MOA of synthetic thyroid hormones?

Activation of T3 receptors,

What are the side effects of synthetic thyroid hormones?

ssx of hyperthyroidism: | Restlessness, insomnia, nervousness, weight loss, afib

What are the common complications of synthetic thyroid hormone in the elderly?

A-fib | Osteoporosis

What is the half life of T3 relative to T4?

1 day compared to 7 days for T4

What is the T4 synthetic?

Levothyroxine

What is the T3 synthetic?

Liothyronine

What is Grave's disease?

Autoantibodies stimulate TSH receptors, and increase the production of T3 and T4

What happens to TSH levels in Grave's disease?

Decreases

What is the effect of increased iodide? How?

hyperthyroidism can be due to underlying disease, or primary

What are the major causes of hyperthyroidism?

Grave's Hashimoto's Thyroid adenoma/carcinoma

What is a thyroid storm?

ACute episode of thyroid activity brought on by stress (surgery, infx, DKA etc)

What is the main secondary cause of hyperthyroidism?

Dysfunction of hypothalamus or pituitary

What is the general class of antithyroid agents? What are the two drugs that fall into this class? MOA?

Thioamides Methimazole Propylthiouracil Inhibition of peroxidase reaction, iodine organification, and coupling of the iodotyrosine in the thyroid colloid

What is the MOA of methimazole?

Thioamides---Inhibition of peroxidase reaction, iodine organification, and coupling of the iodotyrosine in the thyroid colloid

What is the MOA of Propylthiouracil?

Thioamides---Inhibition of peroxidase reaction, iodine organification, and coupling of the iodotyrosine in the thyroid colloid

What are the side effects of the thioamides?

Rash | N/v GI distress

What is the black box warning with Propylthiouracil?

Severe Hepatitis

Why is PTU preferred in pregnancy?

More protein bound, so less likely to cross placenta

What is the drug of choice for thyroid storm? Why?

PTU because is absorbed faster

Which is more potent: methimazole or propylthiouracil?

Methimazole

What are the two Iodides that are used to treat hyperthyroidism? MOA?

Potassium iodide Lugol's solution Inhibit hormone release by inhibiting proteolysis of Tgb

What is the MOA of potassium iodide?

Inhibit hormone release by inhibiting proteolysis of Tgb

What is the MOA of lugol's solution?

Inhibit hormone release by inhibiting proteolysis of Tgb

Why are the iodides only for short term use?

Will only inhibit 2-8 weeks d/t downregulation of Na/I transporter receptor

What will happen with sudden withdrawal of iodides?

Thyrotoxicosis

What are iodides particularly good for?

Thyroid storm or preoperative thyroid problems

What are the adverse effects of Iodides?

ILI Sore gums Metallic tasts

What is the MOA of radioactive Iodine (I-131)?

radioactive beta rays will ablate thyroid tissue

What is the major risk of using I-131?

Total ablation of the thyroid causing hypothyroidism

Is there evidence of CA risk with using Radioactive iodine? Why or why not?

No, since it concentrates in the thyroid

What are the three anion inhibitors? MOA?

perchlorate Pertechnetate Thiocyanate Inhibit Na/I transporter

What is the MOA of Perchlorate?

Inhibit Na/I transporter

What is the MOA of pertechnetate?

Inhibit Na/I transporter

What is the MOA of Thiocyanate?

Inhibit Na/I transporter

What are the adverse effects of perchlorate?

Aplastic anemia

What is the effect of amiodarone on the thyroid? What drug should be used to treat this?

Causes hypothyroidism

What beta blocker is used as an adjuvant agent for treating hyperthyroidism? Why is this used?

Propranolol Inhibits 5'DI Controls heart effects of hyperthyroids

What is the use of diltiazem in treating hyperthyroidism?

Controls techycardia in asthmatic

What is the use of barbiturates in treating hyperthyroidism?

Increased T4 metabolism

What is the use of Bile acid sequestrants in treating hyperthyroidism?

Increase biliary T4 excretion

Thyroid meds Flashcards

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