Thyroid Pharmacology Flashcards
Brief overview of each thyroid disorder
hyperthyroid
hypothyroid
primary & secondary
Hyperthyroid
- primary = overproduction of T4/T3 from the thyroid itself
- thus, in primary: T3/T4 will be high but TSH will be low (negative feedback from pituitary)
- secondary = abnormal pituitary gland: thus TSH is high which makes the T3/T4 high too
Hypothyroid
- Primary = thyroid isnt making enough T3/T4
- thus, in primary, TSH will be high (trying to trigger increase production of T3/T4)
- secondary: nonfunctionig pituitary gland; thus TSH is low and therefore T3/T4 is low
subclinical phases exist: in that the TSH could be high (in hypo) but the T3/T4 is normal rn, and the TSH could be low (in hyper) but the T3/T4 is normal
Hypothyroid
- who are you treating (conditions to treat)
treat everyone with overt hypothyroidism: therefore low T3/T4 and high TSH
treat those with subclinical hypothyroidism: therefore high TSH but normal T3/T4 IF…..
- the TSH is > 10
- there are antibodies (detecting hasimotos)
- symptomatic hypo: weight gain, fatigue, hair loss, dry skin, constipation, menorrhagia, etc
- goiter on PE
Hypothyroid
- gold standard medication
levothyroxine
MOA
watch dosing in what pt.
adjust dosing + monitoring + administration
Levothyroxine
gold standard hypothyroid medication
MOA: synthetic T4: converted to T3 in the peripheral tissue
Be Aware of Dosing For…
- pregnant: increase dose
- older age: decrease dose
- coranary disease: watch arrythmias with inc. doses
- GI disorders: less absorbtion
- has narrow Thearpeudic index & bioequlivence can vary depending on the brand v generic
Dosing Details
- adjust dose ever 3-6 weeks
- if pt. cannot tolerate PO (vomiting) hold med for 5 days : if still cant tolerate PO = give IV
- take with water empty stomach, 1 hour from other meds & 4 hours from DDI meds
Monitoring
- takes 3-6 months to see changes in the TSH to normalize
- once normal, repeat TSH every 6 months
Levothyroxine (hypothyroid)
DDI
(just FYI: said we dont need to know)
things that decrease levo
- amioderone
- estrogen
- iron/calcium
- SSRIs
- bile acid sequesterants
Things that increase levo.
- semaglutide
wathc with warfrain and increased anticoags.
Hypothyroid Medication
Desiccated Thyroid (Armout Thyroid)
MOA
NOt used due to… (side effects)
NOT for… (pt. population)
Desiccated Thyroid (Armour)
- a bioidentical thyroid from cows/pigs
MOA = mimics the action of endogenous thyroid hormone in the body
Side Effects
- hypersensitivity reactions
- unstable bioavalibility & potency of the med
- variable amounts of T3/T4
DO NOT USE IN
- vegan & Vegetarian pop.
- relgious subsets (who cant have pork)
- BEERS LIST MEDICATION: for CVD events = therefore eldery
Desiccated Thyroid (Armour Thryoid)
- titrate dose how often
- monitoring parameters
- warnings
- contraindications
Dosing
- titrate dose every 2-3 weeks
- monitor = HR, BP, new/worsening cardiac symptoms
- take on empty stomach
Warning
- cardiovascular events : becuase the amoutn of T3/T4 is variable need to be aware
Contraindications
- cannot be used in those with an uncorrected adrenal insufficiency
Hypothyroid Medication
Liothyronine
MOA
Titration
Side Effects
Monitoring
Liothyronine
NOT recommended by the AACE: because of its potent cardiovascualr affects and CVD risk
MOA = syntheic T3 (active! thats why it has severe cardio issues)
Dosing
- titration: every 1-2 weeks
Monitoring
- BP
- HR
- Cardiovascualr effects
- bone mineral density
Side Effects
- CVD risks
- osteoporosis
Hypothyroid Medication
Liotriax
MOA
Dosing & titration
Side Effects
Liotriax
not recommened by the AACE: because of teh cadriovascualr risks with active T3 and that it is a set dose of T4/T3 ratio and cannot be adjusted
MOA = synthetic T4:T3 ratio (its levothyroxine & liothyronine) in a 1:4 ratio
Dosing
- Titration = every 2-3 weeks
Side Effects
- cardiovascualr risks
- monitor: BP, HR and new cardiovascualr events
Thyroid Hormone Replacement (hypothyroid medications)
Adverse Drug Reactions
if its giving thyroid hormone: the ADRS will be signs/symptoms of hyperthyroid
- weight lss
- fever
- diarrhea
- HA
- temperature chagnes
- nervousness & anxiety
- Nausea/vomiting
- cardiac abnormalities
Goals of treating hypothyroidism
- resolve clinical symptoms
- reverse biochemical issues
- decreased cholesterol to decreased CVD risk
- prevent myxedema coma & neruologic effects
- prevent dementia-like state in eldery & prevent miscarriage in pregnant & developmental issues in kids
Euthyroid Sick Syndrome
what is it
how do you treatment
Euthyroid Sick Syndrome
- pts. who have abnormalities in the circualtion free thyroid hormones (TSH) , as a result of an underlying severe illness
- this will happen in spetic pts. trauma, cancer, etc.
- most commonly, see low levels of T3 but they do not have underlying thyroid issues
Treatment
- DO NOT given thyroid replacement thearpy
- treat underlying condition and thyroid labs (T3 and TSH) will go back to normal
Myxedema Coma
- what is it
- symptoms/signs
- medications
- Treatment
Myxedema Coma
- life-threatening and severe decompensated hypothyroid: extreme hypothyroidism
Symptpms
- thick, non-pitting edema
- AMS
- hypotensions, hypothermia, hyponatremia
- hypoventilation
- coma not required
precipated by….
- infection, trauma, heart failure
- medications: beta, blockers, anesthesia, narcotics, seditives, lithium, amioderone, phenyotoin
Treatment
- IV thyroid replacement: levothyroxine (T4) or liothyronine (if they need to be recovered very quickly)
- give Abx. if infection
- steroids
- supprotive treatmetn (ventilation, etc.)
Monitor
- VS, consciousness & TSH levels
-
Hyperthyroid treatment
who are you initiating treatment in
those with overt hyperthyroid: elevated T4/T3 with low TSH
those with subclinical hyperthyroid (low TSH but normal T4/T3) IF….
- TSH < 0.1
- those with postive tests for Grave’s Disease
- those who are postmenopausal
- those with cardiovascualr disease
Hyperthyroid Treatment
gold standard
Methimazole
MOA
who should use this med
pregnancy consideration
dosing based on what
Methimazole
gold standard medication for hyperthyroid
MOA = thiourea: inhibits iodination and synthesis of teh thyroid hormones in the thyroid gland
Positives
- longer half-life
- lower cost
- less hematologic effects
Pregnancy
- cannot be used in the 1st trimester : use PTU instead
Dosing
- the dosing is based on the Free T4 levels of the pt.
Methimazole
Treatment Duration (for those undergoing definitative thearpy or not)
those undergoing definative therapy: aka taking RAI or getting thyroidectomy
- take med until they get to euthyroid state
- discontinue the med 2-3 days prior to starting radioactive iodine therapy (RAI)
- discontinue on day of surgery for thyroidectomy
those NOT undergoing definitive therapy
- if they are dx. with Grave’s Disease = continue med for 8-12 months then assess labs
- if they are dx. with toxic mulinodular goite/adenoma: continue med indefinately
Hyperthyroid Medication
Propylthiouracil (PTU)
MOA
Role in Therapy
Dosing
PTU
MOA = thiourea: more potent that methimazole & works in the peripheral tissue to decrease T3 levels as well
Drug of choice for those pregnant in the first trimester: P for Pregnancy !!!
Used for
- pregnancy (1st tri)
- for those in thyroid storm (since so potent)
Dosing
- for severe hyperthyroid or large goiter = increase dose
Thioureas (methimazole & PTU)
Adverse Drug Reactions
Hepatotoxicity: Black Box Warning with PTU about this (aka life threatening)
- monitor LFTs at baseline and at 3-6 months
Maculopapular rash
- variable & spontaneously resolves self
Lupus Like Syndrome & Arthraligas (joint pain)
- typically after 6 months of med
Agranulocytosis
- need to monitor WBC
Fever
Thioureas (methimazole and PTU)
Monitoring Parameters
- TSH & T4
- CBC
- LFTS
Monitoring
TSH and T4
- monitor every 4-6 weeks until euthyroid achieved
- then monitor every 3-6 months
CBC
- watch leukopenia
- watch agranulocytosis
- agranulocytosis (more commony with PTU)
- IF agranulocytosis occurs: STOP med immediately and DO NOT rechallenge or restart
LFTS baseline and 3-6months
will see signs of clinical improvement (symptom resolution) in 4-8 weeks
Hyperthyroid Medication
Radioactive Iodine (RAI)
MOA
popultaions preferred to use in
RAI : radioactive Iodine
MOA = inhibits the release of store thyroid hormone
- able to concentrate within the thyroid tissue specifically to avoid necrosis of the tissue
- helpful and used to reduce the size of the thyroid tissue prior to surgery
Populations to use RAI in
- elderly
- those with a cardiac diagnosis
- those with multinodular goiter
- those who have failed medication therapy
RAI
side effects/ADRS
contraindicated in….
when do you see improvement
RAI: radioactive iodine for hyperthyroid
Cons
- some fear swallowing radioactive substances
- hypothyroidism likely to develop: then you treat that
- CONTRAINDICATED IN PREGNANT OR BREASTFEEDING
Adverse reactions
- metallic taste
- soreness in the mouth
- hypothyroid develops
euthyroid effecs after 6 months
Hypperthyroid Treatmetn
Iodine
- types
- MOA
- when its used
- ADRs
Types of Iodine
- lugol’s solution
- satueratede solutions of potassium iodine (SSKI)
MOA = inhibit thyroid release of hormones when there is a prence of excess iodine: less T3/T4 produced
When its Used
- least prefered
ADRS
- hypersensitivity
- palpaltations
- depression
- weight loss
- gynecomastia
- these are significant and therefore rarely used
Hyperthyroid Treatment
Ablative Surgery
- who shold consider this
- down sides
- adeverse Effects
Ablative Surgery
Consider In…
- extremely large thyroid glands
- those with severe opthomapathy
- those not responding to medication treatment
Down Sides
- morbidity
- recurreing hyperthyroid
- invasive, painful & scarring
- expensive
Adverse Effects
- hypothyroid
- voal cord issue if recurrent laryngeal nerve impacted
Role of Nonselective Beta Blockers in Hyperthyroid
- names
- when are they used
- do not use in who
- specifics of each med
Propranolol and Nadolol
- a small therapeduic effect: but can help block the hyperthyroid manifestations of palpations, etc.
goald HR: < 90
- used as adjunctive add-on therapy
Contraindicated in
- bronchial asthma
- heart block in the first degree
Propranolol
- use in breastfeeding moms
- most studied for hyperthyroid effects
Esmolol
- used for thyroid strom in ICU
Non-Dihydropyridine Calcium Channel Blockers for Hyperthyroidism
- names
- when used
- contraindications
Diltiazem and Verapamil
when are they used
- add on therapy but cannoy used a beta blocker
Contraindications
- those with 2nd or 3rd degree heart block
- acute MI
- pulmonary congestion
- hypotension (systolic < 90)
