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NAPLEX Content > Thyroid Disorders > Flashcards

Thyroid Disorders Flashcards

1
Q

Which is more potent? T3 or T4?

A

T3 is more potent than T4, but has a much shorter half-life

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2
Q

What regulates thyroid hormone production?

A

Thyroid stimulating hormone (TSH or Thyrotropin)

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3
Q

Effects of elevations of T4 levels?

A

Elevations in T4 levels => inhibits secretion of TSH and create a
negative feedback loop

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4
Q

Which is measured, T3 or T4? Why?

A

Free T4 (FT4) levels

This is the active form (T4)

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5
Q

Xtics of Hypothyroidism?

A

Deficiency of T4 => elevation in TSH

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6
Q

Xtics of Hyperthyroidism?

A

Oversecretion => low level of TSH

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7
Q

Main causes of Hypothyroidism?

A

Hashimoto’s dx - most common cause

Drugs (Amiodarone, Inteferons, Lithium, Nitroprusside, Tyrosine kinase inhibitors, Sunitinib - most notable)

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8
Q

Clinical s/sx of Hypothyroidism?

A

Cold intolerance

Dry skin

Fatigue

Weight gain

Hoarseness

Coarseness or loss of hair

Heavier than normal menstrual periods (menorrhagia)

Memory and mental impairment

Goiter

Myalgias

Weakness

Depression

Constipation

Bradycardia

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9
Q

Complications of Hypothyroidism?

A

CVD (cardiomyopathy, HF, hyperlipidemia, CAD)

Goiter

Depression

Infertility

Myxedema - intense cold intolerance, drowsiness, unconsciousness

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10
Q

Effects of hypothyroidism on body metabolism?

A

Hypothyroidism causes the body to SLOW down

T/4 u see classic sx of low metabolism - fatigue, weight gain

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11
Q

What’s the most common cause of Hypothyroidism?

A

Hashimoto’s dx

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12
Q

Diagnosis of Hypothyroidism?

A

Low free thyroxine (low FT4) - normal range 0.7-1.9 ng/dL

High thyroid stimulating hormone (high TSH) - normal range 0.3-3.0 mIU/L

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13
Q

Monitoring of hypothyroidism?

A

Check free T4 and TSH levels Q6-8 wks, until levels are normal

Then 6 months later, then yearly

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14
Q

What’s FDA pregnancy category A for hypothyroidism?

A

Levothyroxine

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15
Q

DOC in hyperthyroidism?

A

Levothyroxine (T4)

Imp to use a consistent preparation

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16
Q

What can be used to supplement Levothyroxine (T4)?

A

Liothyronine (T3, Cytomel and Triostat)

Or

Desiccated thyroid (T3 & T4, Armour Thyroid) - not usually favored

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17
Q

How should thyroid replacement therapies be used?

A

Take thyroid replacement in the morning, first thing, on an empty stomach, at least 30 mins b4 breakfast

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18
Q

Is iodine supplement used in mgt of hypothyroidism?

A

No!

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19
Q

List hypothyroid tx agents

A

Levothyroxine (T4) - (Synthroid, Levothroid, Levoxyl)

Thyroid Desiccated USP (T3 and T4) - (Armour Thyroid, Nature-Throid, Westhroid, NP thyroid, WP Thyroid)

Liothyronine (T3) -(Cytomel, Triostat) tablet, inj

Liotrix (T3 and T4 in 1:4 ratio) - (Thyrolar)

20
Q

Brand name of Levothroxine (T4)? Used in hypothyroid tx?

A

Synthroid

Levothroid

Levoxyl

21
Q

Are all generic Levothyroxine bioequivalent?

A

No!

Check AB-rating

22
Q

IV to PO ratio of Levothyroxine?

A

IV to PO ratio = 1:2

23
Q

Drugs that decrease thyroid hormone levels?

A

Aluminum (antacids)

Calcium

Cholestyramine

Iron

Mg

Multivitamins (containing ADEK, folate, iron)

Orlistat (Xenical, Alli)

Sevelamer

Sodium polystyrene (Kayexalate)

Sucralfate

Lanthanum

CBZ, phenobarbital, PHT, rifampin

SSRIs
Separate doses by 4 hrs

24
Q

Effect of Thyroid hormone on anticoagulant?

A

Increases effect of anticoagulants (increased PT/INR with warfarin)

25
Q

Effect of Thyroid hormone on Digoxin, Theophylline, Antidiabetic meds?

A

Reduce digoxin, theophylline levels and effect of antidiabetic agents

26
Q

Xtics of Hyperthyroidism (Thyrotoxicosis)?

A

High FT4 and low TSH

27
Q

Main causes of Hyperthyroidism?

A

Graves dx

28
Q

Clinical s/sx of Hyperthyroidism?

A

Heat intolerance or increased sweating

Weight loss (or gain)

Agitation, nervousness, irritability, anxiety

Palpitations and tachycardia

Fatigue and muscle weakness

Freq bowel movements or diarrhea

Insomnia

Light or absent menstrual periods

Goiter

Thinning hair

Tremor

Exophthalmos (exophthalmia), diplopia

29
Q

Drugs that can cause hyperthyroidism?

A

Iodine

Amiodarone

Interferons

Any pt taking excessive doses of any forms of any available forms of thyroid hormone

30
Q

Tx of choice of for Grave’s dx?

A

Radioactive iodine (RAI-131)

31
Q

Role of beta-blocker in grave’s dx?

A

Beta-blocker should be given first for sx control (to reduce palpitations, tremors and tachycardia)

32
Q

Mao of Thionamides (used for Hyperthyroid tx)?

A

Inhibits synthesis of thyroid hormones by blocking the oxidation of iodine in thyroid gland

PTU also inhibits peripheral conversion of T4 to T3

33
Q

Drugs used for hyperthyroid tx?

A

Propylthiouracil (PTU) - (Propyl-Thyracil)

Methimazole (Tapazole)

34
Q

BBW of Propylthiouracil (PTU) - (Propyl-Thyracil) & Methimazole (Tapazole) - used for hyperthyroid tx?

A

Severe liver injury and Acute liver failure (with PTU)

35
Q

SEs of Propylthiouracil (PTU) - (Propyl-Thyracil) & Methimazole (Tapazole) - used for hyperthyroid tx?

A

GI upset

SLE-like syndrome

Hepatitis

Agranulocytosis (rare) - see MD at once if u develop yellow skin, abdominal pain, high fever or severe sore-throat

36
Q

How do u use Propylthiouracil (PTU) - (Propyl-Thyracil) & Methimazole (Tapazole) - used for hyperthyroid tx - in pregnancy?

A

Propylthiouracil (PTU) - (Propyl-Thyracil) - preferred in 1st trimester

Methimazole (Tapazole) - used in 2nd and 3rd trimesters

Due to increased risk of liver toxicity from PTU

37
Q

Hyperthyroid tx preferred in thyroid storm?

A

Propylthiouracil (PTU) - (Propyl-Thyracil)

38
Q

Is PTU first-line in hyperthyroidism?

A

No!

Except in pts who can’t tolerate other options or conditions where other antithyroid therapies are CI

39
Q

Iodides - used in hyperthyroidism?

A

Potassium Iodide + Iodine Solution (Lugol’s solution) used off-label

Saturated soln of Potassium Iodide (SSKI, ThyroShield)

40
Q

MOA of Iodides - used in hyperthyroidism?

A

Temporary inhibit secretion of thyroid hormones; T4 and T3 levels will be reduced for several weeks, but effect will it be maintained

41
Q

What’s thyroid storm?

A

Life-threatening medical emergency caused by decompensated hyperthyroidism

42
Q

S/sx of thyroid storm?

A

Fever > 103 degree F

Tachycardia

Tachypnea

Dehydration

Profuse sweating

Agitation

Delirium

Psychosis

Coma

43
Q

Tx of thyroid storm?

A

PTU 900-1200mg PO - divided Q4-6 hrs
+
Inorganic iodide therapy such as, SSKI 3-5 drops PO Q8H or
Lugol’s soln 5-10 drops PO Q8H (iodine to be given 1 hr AFTER PTU)
+
Beta-adnerergic blockage (eg. Propranolol 40-80 mg PO Q6H)
+
Corticosteroid therapy (eg. Dexamethasone 2-4 mg PO Q6H)
+
Aggressive cooling with APAP + cooling blankets + other supportive tx (eg. Antiarrhythmics, Insulin, Fluids, Electrolytes, etc)

44
Q

Pregnancy category of Levothyroxine (Synthroid, Levoxyl)?

A

A

45
Q

Role of thyroid gland?

A

One of the largest organs within the body’s endocrine system and is the only organ which contains cells that have the ability to ABSORB iodine

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