Thyroid Disorders Flashcards by Grace Whitham

What 2 thyroid hormones are produced by the thyroid gland?

triiodothyronine (T3)

thyroxine (T4)

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The thyroid gland is the only organ that can absorb what molecule?

Iodine

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Which is more potent T3 or T4?

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Which has a shorter half-life T3 or T4?

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What is thyroid hormone production regulated by?

thyroid-stimulating hormone (TSH)

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Which is the active form T3 or T4?

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When the level of (T3/T4) increases, it inhibits the secretion of TSH

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In hypothyroidism T4 is (high/low) and TSH is (high/low)

T4: low
TSH: high

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What is Hashimoto’s disease

Autoimmune condition in which antibodies attack the thyroid gland causing hypothyroidism

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What is Myxxedema coma?

Life-threatening emergency characterized by poor circulation, hypothermia, and hypometabolism
Cause by chronically untreated hypothyroidism
Initial treatment: IV levothyroixine

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S/Sx hypothyroidism

Cold intolerance
Dry skin
Fatigue
Muscle cramps
Constipation
Weight gain
Goiter
Depression
Bradycardia
Menorrhagia
Memory and mental impairment
Coarse hair or loss of hair

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What drugs can cause hypothyroidism?

I TALC
Interferons
Tyrosine kinase inhibitors (e.g. sunitinib)
Amiodarone
Lithium
Carbamazepine

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What is normal free T4? TSH?

T4: 0.9-2.3 ng/L

TSH 0.3-3 mIU/L

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When initiating hypothyroidism treatment, how often should you monitor TSH?

every 4-6 weeks

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What is DOC for hypothyroidism?

Levothyroxine (T4)

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Why is iodine deficiency rare? How can you treat it if it does occur?

In US most salt is iodized

Can supplement with multivitamin

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Levothyroxine initial dosing

1.6 mcg/kg/d (IBW)

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Levothyroxine warnings, monitoring

Warnings: decrease dose in CV disease, can decrease BMD and lead to fractures
Monitoring: TSH levels and clinical symptoms every 4-6 weeks until levels are normal

Levothyroxine IV to PO ratio

IV: PO

0.75:1

Levothyroxine tablet colors

Orangutans Will Vomit On You Right Before They Become Large, Proud Giants
Orange - 25
White - 50
Violet - 75
Olive - 88
Yellow - 100
Rose - 112
Brown - 125
Turquois - 137
Blue - 150
Lilac - 175
Pink - 200
Green - 300

What drugs decrease levothyroxine absorption?

Separate by 4 hours: Antacids and polyvalent cations containing iron, calcium, aluminum, or magnesium, multivitamins (ADEK, folate, iron), cholestyramine, sevelamer, and sucralfate

Thyroid hormone replacement can increase effects of ___ and decrease effects of ___

Increase warfarin (Increased INR)
Decrease theophylline (asthma/COPD)

Levothyroxine PO administration counseling notes

Take 60 minutes before breakfast or at bedtime at least 3 hours after a meal
Take with water

What is thyrotoxicosis?

Hyperthyroidism

TSH and T4 values in hyperthyroidism

TSH: low | free T4: high

S/sx of hyperthyroidism

``` Heat intolerance or increased sweating Weight loss Agitation, nervousness Palpitations or tachycardia Frequent bowel movements Insomnia Thinning hair Exophthalmos (protrusion of eyeballs) Light or absent menstrual period ```

Most common cause of hyperthyroidism

Grave's disease

What is Grave's disease

Autoimmune disease where antibodies stimulate thyroid to produce too much T4

What drugs can cause hyperthyroidism?

Iodine Amiodarone Interferons

How is hyperthyroidism treated?

Destroying part of the thyroid via radioactive iodine (RAI-131) or surgery Patient is managed with Propylthiouracil (PTU) or methimazole while waiting for surgery Need to treat at high dose for 1-3 months before symptoms control is complete

What medications are thionamides

Propylthiouracil (PTU) | Methimazole

Thionamide MOA

Inhibit synthesis of thyroid hormones by blocking the oxidation of iodine in the thyroid gland PTU also inhibits peripheral conversion of T4 to T3

Thionamide BBW, warnings, SE, and notes

BBW: (PTU) severe liver injury and acute liver failure, pregnancy (PTU preferred in 1st trimester) Warnings: hepatotoxicity, agranulocytosis, DILE SE: GI upset Notes: methimazole is usually DOC; PTU is preferred in thyroid storm and in 1st trimester of pregnancy

Iodides MOA

temporarily inhibit secretion of thyroid hormones

Levothyroxine (T4) brand names

Synthroid Levoxyl Unithroid

Thyroid, Desiccated (T3 and T4) brand names

Armour Thyroid

Liothyronine (T3) brand names

Cytomel

Why is potassium iodide used after radiation exposure?

It blocks the accumulation of radioactive iodine in the thyroid gland, preventing thyroid cancer

What is thyroid storm?

Life-threatening medical emergency Decompensated hyperthyroidism that can be precipitated by infection, trauma, surgery, radioactive iodine treatment, or non-adherence to anti-thyroid medication

S/sx of thyroid storm

``` Fever >103 F Tachycardia Tachypnea Dehydration Profuse sweating Agitation Delirium Psychosis Coma ```

How to treat thyroid storm?

``` Anti-thyroid drug therapy (PTU) Inorganic iodide therapy (SSKI) or Lugols' solution Beta blockers (propranolol) Systemic steroid (dexamethasone) Aggressive cooling ```

How to treat hypothyroidism in pregnancy - what adverse outcomes can occur if left untreated?

Levothyroxine is DOC - will require 30-50% dose increase | Untreated can lead to loss of pregnancy, low birth weight, premature birth, lower IQ

How to treat hyperthyroidism in pregnancy - what adverse outcomes can occur if left untreated?

If treatment is necessary: antipthyroid drugs (PTU first trimester, methimazole in 2nd and 3rd) Untreated can lead to loss of pregnancy, low birth weight, thyroid storm, maternal HTN and CHF, seizure disorder in baby