Thyroid Flashcards
T4 or T3 is more potent?
T3
Thyroid hormones will cause ________ sensitivity
cathecholamine
_____ has to be converted to _____ before it can bind (T4 or T3 in which blank?
T4 –> T3
Process of biosynthesis of thyroid Hormones:
1st step:
_____ enters from ______ via ______
iodine; plasma; Na symporter
Process of biosynthesis of thyroid Hormones:
2nd step
____, an iodine channel, puts Iodine into the follicle ____
pendrin; colloid
Process of biosynthesis of thyroid Hormones:
3rd Step
Iodine is oxidized into _____ or _____
MIT or DIT
aka mono-iodine or di-iodine
Process of biosynthesis of thyroid Hormones:
4th step:
Iodine gets added to ________
thyroglobulin
Process of biosynthesis of thyroid Hormones:
5th step:
_________ of rings occurs
conjugation
Process of biosynthesis of thyroid Hormones:
6ht step
_______ produces protein and either thyroxine or triiodothyronine
Proteolysis
Hypothalamus release ______ to stimulate ______ pituitary
TRH; anterior
Physiological effects of thyroid hormones
- growth/development
- Thermoregulation
- BMR
- Protein Synthesis
- Catecholamine Sensitivity
Physiological effects of thyroid hormones
Growth and Development:
No T3 leads to _______ which is essential for ____ development
cretinism; brain
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)
Physiological effects of thyroid hormones:
Metabolic Effects
- increase _____ and ____
BMR; oxygen consumption
Physiological effects of thyroid hormones:
Metabolic Effects
starvation will decrease _____ and thyroid receptor
T3
Physiological effects of thyroid hormones:
Thermogenesis
________ (increase or decrease) resting heat production
increase
Metabolism of Thyroid hormones:
it gets ________
it will be excreted in ______
deiodized; the bile;
Causes of HYPOthyroidism
- Hashimotos Thyroiditis
- Destruction of removal of gland
- iodine deficiency
- Congenital
- Secondary - TSH deficiency
Hypothyroidism has nontoxic or toxic goiter
NONTOXIC! (thyroid is just stimulated a lot bc of low thyroid)
Hyperthyroidism has nontoxic or toxic goiter
toxic! seen in graves disease
possible causes of Hyperthyroidism
- graves disease
- Adenoma making T3 (multi or uni nodular goiter)
- subacute thyroiditis
Toxicity that can be seen with thyroid hormone replacement therapy
- nervousness
- heat intolerance
- weight loss
- tachycardia
- atrial fibrillation
what is subactue thyroiditis
viral infection of thyroid gland
what is graves disease
autoimmune thyroid stimulating IgG
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
