Thyroid Flashcards by Kappa Epsilon Pi Chapter

T4 or T3 is more potent?

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Thyroid hormones will cause ________ sensitivity

cathecholamine

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_____ has to be converted to _____ before it can bind (T4 or T3 in which blank?

T4 –> T3

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Process of biosynthesis of thyroid Hormones:
1st step:
_____ enters from ______ via ______

iodine; plasma; Na symporter

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Process of biosynthesis of thyroid Hormones:
2nd step
____, an iodine channel, puts Iodine into the follicle ____

pendrin; colloid

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Process of biosynthesis of thyroid Hormones:
3rd Step
Iodine is oxidized into _____ or _____

MIT or DIT

aka mono-iodine or di-iodine

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Process of biosynthesis of thyroid Hormones:
4th step:
Iodine gets added to ________

thyroglobulin

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Process of biosynthesis of thyroid Hormones:
5th step:
_________ of rings occurs

conjugation

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Process of biosynthesis of thyroid Hormones:
6ht step
_______ produces protein and either thyroxine or triiodothyronine

Proteolysis

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Hypothalamus release ______ to stimulate ______ pituitary

TRH; anterior

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Physiological effects of thyroid hormones

growth/development
Thermoregulation
BMR
Protein Synthesis
Catecholamine Sensitivity

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Physiological effects of thyroid hormones
Growth and Development:
No T3 leads to _______ which is essential for ____ development

cretinism; brain

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Physiological effects of thyroid hormones:
Protein Synthesis
(anabolic or catabolic) at normal levels
and
(anabolic or catabolic) at elevated levels

anabolic; catabolic (at high thyroid levels - BMR too high proteins will be broken down)

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Physiological effects of thyroid hormones:
Metabolic Effects
- increase _____ and ____

BMR; oxygen consumption

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Physiological effects of thyroid hormones:
Metabolic Effects
starvation will decrease _____ and thyroid receptor

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Physiological effects of thyroid hormones:
Thermogenesis
________ (increase or decrease) resting heat production

increase

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Metabolism of Thyroid hormones:
it gets ________
it will be excreted in ______

deiodized; the bile;

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Causes of HYPOthyroidism

Hashimotos Thyroiditis
Destruction of removal of gland
iodine deficiency
Congenital
Secondary - TSH deficiency

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Hypothyroidism has nontoxic or toxic goiter

NONTOXIC! (thyroid is just stimulated a lot bc of low thyroid)

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Hyperthyroidism has nontoxic or toxic goiter

toxic! seen in graves disease

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possible causes of Hyperthyroidism

graves disease
Adenoma making T3 (multi or uni nodular goiter)
subacute thyroiditis

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Toxicity that can be seen with thyroid hormone replacement therapy

nervousness
heat intolerance
weight loss
tachycardia
atrial fibrillation

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what is subactue thyroiditis

viral infection of thyroid gland

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what is graves disease

autoimmune thyroid stimulating IgG

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Thyroid Replacement Therapy Options: | Natural replacement comes form bovine and porcine - ______ blood levels tho

variable - inconsistent then - not good for thyroid!

Thyroid Replacement Therapy Options: Synthetic thyroid: Levothyroxine is (T3 or T4) and has a (slow or fast) onset?

T4; slow (slow bc T4 --> T3)

Thyroid Replacement Therapy Options: Synthetic Thyroid Liothyronnine is (T3 or T4) and has a (slow or fast) onset?

T3; fast!

Thyroid Replacement Therapy Options: Synthetic Thyroid Liotrix is (T3 or T4) and has a (slow or fast) onset?

its a mixture of both T3 and T4! more T4 than T3) not sure about timing...

Main Options for Treating Hyperthyroidism

- Antithyroid Drug Therapy (Thioamides) - Thyroidectomy - Destruction of gland w/ radioactive iodine - Other drug therapies....

Metabolism of thyroid hormones: | ______ to form glucuronide or sulfate w/ phenolic group

conjugated

Metabolism of thyroid hormones: | conjugated to form glucuronide or sulfate w/ __________

phenolic group

What are some "off label" drugs that are used to treat hyperthyroidism/help with symptoms - and how do they help?

- Propranolol (for tachycardia) - Diltiazem (for tachycardia) - Barbiturates (inducing enzymes that will lower T4 levels) - Bile acid sequesterants: lower t4 levels by increasing excretion

What drugs are Thioamides

- methimazole | - propylthiouracil

Thioamides are used to treat ________

thyrotoxicosis

Thioamides inhibit _______ to block ______ and ________

inhibit thyroid peroxidase; block iodine organification and coupling of iodotyrosines

Thioamides - onset is ~ _______

3 - 4 weeks aka kinda slow

Side effects of Thioamides

- Nausea/GI distress - Altered sense of taste and smell (methimazole) - Maculpapular pruritic rash (most common) - Agranulocytosis

what is "iodine organification"

I- is put on thyroglobulin with the help of H2O2 as the oxidizer

Radioactive Iodine used for Hyperthyroidism: - ____ is emitted - localized destruction of _______ - Can pregnant women/nursing moms do this? - is administered as _______

B-rays; thyroid follicles; No!; Na(131)I

Larges dose of _______ inhibits iodine organification

Iodine

what is Lugols Solution? and what is it used for

Aqueous solution of elemental I and KI; used as an antiseptic/disinfectant

Treatment for Thyroid Storm

- KI solution - beta-blocker - antithyroid drugs

Electrophysiology of the Heart: K+ channel or Na+ Channel - which one has a very quick onset and which one has a slower onset?

K+ - slower | Na+ - fast

Explain the components of the resting membrane potential

Na/Ca on outside of cell and K+ inside cell | V. Positive outside

Explain components of the depolarization membrane potential

Na+ comes INTO the cell which makes the inside of the cell positive

Explain components of the repolarization membrane potential

K+ goes to the outside of the cell - to make the inside of the cell negative again.

what is HCN channel

hyperpolarization activated cyclic nucleotide gated channel - NON SELECTIVE CATION channel

HCN channel is responsible for the _______ current

pacemaker

Pacemaker Current: determines the rate of what?

diastolic depolarization

Sympathetic Control of Heart: | Sympathetic Nerve will release ______

norepinephrine

Sympathetic Control of Heart: | NE binds to _______ receptor and ________ the concentration of cAMP which activates ________

beta-adrenergic; increases; HCN channel

Sympathetic Control of Heart: | Activating HCN Channel will _______ diastolic Na+ conductance will ______ time to next spike

INCREASE; shorten

Parasympathetic Control of Heart: | _________ will bind to _______ and Gby is released from Ga

acetylcholine; Muscarinic

Parasympathetic Control of Heart: | the _______ channel is involved

K+; GIRK

Parasympathetic Control of Heart: | increased K+ conductance causes __________ and ____ time to next spike

hyperpolarization; delays

Selected Thyroid Tests for Adults

TSH/Free T4; Test for Autoimmunity: ATgA; TPO-Ab; TRAb

Drug Inducing Causes for Hyperthyroidism:

Iodinated Compounds Amiodarone Interferons Lithium

Treatment Options for Hyperthyroidism

- Thioamides (Propylthiouracil, Methimazole) - RAI (radioactive iodine) - Surgery (thyroidectmy)

Drug of Choice for Hyperthyroidism and WHY?

Methimazole; | Once a day dosing, good for 2nd and 3rd trimester, no black box warning; Does NOT need renal adjustment

Why would propylthiouracil be a good choice for hyperthyroidism?

- if 1st trimester of Pregnancy | - if pt has thyroid storm issue (because it blocks T4-->T3 conversion

which thioamide needs renal adjustment?

propylthiouracil

Thioamide Adverse Effects:

GI - N/V - take with meals (divided doses) Rash - can be systemic or non systemic; Agranulocytosis Hepatitis

Thioamide Adverse Effects: | If pt comes in and has maculopapular rash and no systemic symptoms - what should be done?

give diphenhydramine/other antihistamines - and try another thioamide

Thioamide Adverse Effects: | If pt comes in has wheals/hives/SOB - what should be done?

this is "anaphylactoid type 1" - stop drug! and do NOT try a different thioamide - must do surgery or RAI

Warning Signs for pt to know about if thioamide causes Agranulocytosis

- flu like symptoms/FEVER (bc have low neutrophil count)/mouth sores/sore throat

how often to check for efficacy of a thioamide

Q4 - 8 weeks until euthyroid;

RAI - treatment for hyperthyroidism: | __________ of thyroid gland with ________ isotope

SLOW DESTRUCTION; radioactive (131)I

Note about RAI for hyperthyroidism and Pregnancy

CONTRAINDICATED: separate pregnancy/lactation/planning pregnancy for 4 -6 months

How does a pt take RAI?

in water- colorless/tasteless

Counseling Points for RAI:

Avoid physical contact due to possible radioactive emission ~ 5 days (avoid kids and babies!) Also note about not trying to become pregnant

In Hyperthyroidism avoid what kind of agents?

agents with intrinsic sympathomimetic activity (acebutolol, carteolol, penbutolol, pindolol)

What are possible adjunctive treatments for Hyperthyroidism?

Use Cardioselective Beta-Blockers! (only for short term - just to control HR) - Propranolol, Metoprolol, Atenolol (Alt. Calcium channel blockers - Diltiazem/Verampil)

Drug Induced Causes for Hypothyroidism

- Amiodarone - Lithium - Interferons - Bexarotene

Possible Hypothyroid Supplements

- LEVOTHYROXINE (1st choice!) - Liothyronnine - Liotrix - Dessicated Thyroid (Natural option)

Dosing for healthy adult for thyroid supplementation

1/6 mcg/kg/day | use IBW for obese patients

starting dose of levothyroxine for elderly patient with hypothyroidism

<1.6 mcg/kg/day | aka start 25 - 50 mcg/day

starting dose of levothyroxine for CVD patient with hypothyroidism

start 12.5 mcg/day - 25 mcg/day

starting dose of levothyroxine for patient that has had hypothyroidism for more than 1 year

start 25 mcg/day

Liothyronine is ____ (T3 or T4)

T3 - rapidly absorbed

Liothyronine has what kind of risk

cardiac toxicity - because rapid absorption of T3 --> hyperthyroid symptoms possible

Possible reasons for a patient to still have high/fluctuating TSH despite a high levothyroxine dose (> 200 mcg/day)

- poor adherence - drug-food interaction - drug-drug interaction

Drug Interactions for levothyroxine that will decrease T4 absorption

- bile acid sequestrant - Antacids - Ferrous Sulfate - Calcium supplement - Sucralfate

Drug Interactions for levothyroxine that will increase serum TBG concentration

Estrogen

Drug Interactions for levothyroxine that will increase the T4 requirement/cause more of a need for supplementation

- Enzyme inducers! (Phenytoin, phenobarbitol, carbamazepine, rifampin)

Levothyroxine and pregnancy: adjust by _____ mcg and check every _______

25; trimester

Immediately after delivery of baby ---- levothyroxine dose should _______ and be checked _______

resume to original (pre-pregnancy) dose; in 6 - 8 weeks