Thyroid Disorders Part 2 Flashcards
State of excessive levels of T3 and T4
Thyrotoxicosis
Increased state of thyroid function
Hyperthyroidism
What causes primary hyperthyroidism?
Excessive release of T3 and T4 by thyroid
What causes secondary hyperthyroidism?
Excessive release of TSH by pituitary
What causes tertiary hyperthyroidism?
Excessive release of TRH by hypothalamus
What is the epidemiology of thyrotoxicosis?
5% of women >60 y/o, women (5x more common), smokers, + family history of autoimmune thyroid disease
What is the most common cause of thyrotoxicosis?
Graves’ disease
Describe Graves’ disease
Autoantibodies bind TSH receptor in thyroid gland, causing excessive thyroid function
Thyroid stimulating Ig is most common (65%), but can also see anti-TPO (75%) and anti-Tg (55%)
What is the most common onset of Graves’ disease?
Women ages 20-40
What are s/s of Graves’ disease in addition to s/s of thyrotoxicosis?
Infiltration opthalmopathy and infiltration dermopathy
B/c Igs like extraocular muscles and skin
What is another name for thyroid-stimulating Ig lab test?
TSH receptor antibodies, TSHrAb
Why would you order a TSI (thyroid-stimulating Ig)?
Assist with diagnosis of Grave’s disease as a follow-up to abnormal thyroid function studies
What factors can interfere with readings of TSI
Recent administration of radioactive iodine (can suppress Ig)
Titers may not decline for up to 1 year after treatment so not used for treatment monitoring
If a TSI is ordered and comes back high, what is the interpretation?
Graves Disease or neonatal thyrotoxicosis
Could elevated TSI during pregnancy cause hyperthyroidism in a fetus/neonate?
Yes
What are etiologies of thyrotoxicosis?
Excessive iodine, thyroiditis, thyroid nodules, medications, hCG, thyrotoxicosis factitia, ectopic thyroid tissue, TSH hyper secretion
What are causes of excessive iodine leading to thyrotoxicosis?
Iodinated radiocontrast dye, high-iodine foods, medications: potassium iodine, amiodarone, iodinated topical antiseptics (povidone iodine)
Amiodarone is 37% iodine!
What are causes of thyroiditis leading to thyrotoxicosis?
Infectious/subacute thyroiditis, silent/postpartum thyroiditis
What are causes of thyroid nodules that can lead to thyrotoxicosis?
Toxic multinodular goiter, single toxic adenomas
What medications can cause thyrotoxicosis?
Chemotherapy and MS medications
What can cause elevated hCG leading to thyrotoxicosis?
Pregnancy, gestational trophoblastic disease, testicular cancer
What can cause thyrotoxicosis factitia leading to thyrotoxicosis?
Intentional or accidental ingestion of exogenous thyroid hormone
What can cause ectopic thyroid tissue leading to thyrotoxicosis?
Struma ovarii, metastatic thyroid cancer
What are symptoms of thyrotoxicosis?
General: fatigue and weakness, weight loss with increased appetite
Psych: nervousness/restlessness, hyperactivity/irritability
Cardio: palpitations/angina
MSK/neuro: muscle cramps
GI/GU: polyuria, diarrhea
Endo/reproductive: heat intolerance and sweating, oligomenorrhea
All of your metabolic processes are sped up including GI/GU muscles—>polyuria, diarrhea; heart: palpitations, brain: hyperactive
You are already so ramped up you can’t stand more heat!
Your body is working over time so it’s tired and it’s breaking things down so you lose weight and want to eat
What are signs of thyrotoxicosis?
General: thin body habitus (you are breaking stuff down and metabolism sped up!)
Psych: agitation, restlessness (so amped up!)
Cardio: tachycardia, atrial fibrillation
MSK/Neuro: muscle weakness (protein catabolism), hyperreflexia, osteoporosis, fine resting tremors
Endo/reproductive: goiter/thyromegaly
Skin: warm, moist skin
Eyes: lid lag or lid retraction
What are manifestations of Graves opthalmopathy?
Upper eyelid retraction
Lid lag with downward gaze
Staring appearance
May see conjunctival edema and inflammation
What are manifestations of thyroid acropachy?
Digital clubbing
Swelling of fingers and toes
Periosteal reaction of extremity bones
This is a rare skeletal complication of Grave’s disease
What are manifestations of Graves dermopathy?
Erythematous, rough plaques
Lymphoid infiltration and glycosaminoglycans accumulation in affected skin
Glycosaminoglycans are polysaccharides involved in cell growth/proliferation
What are cardiopulmonary manifestations of thyrotoxicosis?
Forceful heartbeat
Exertional dyspnea, pulmonary HTN (49%)
Abnormal conduction: premature atrial contractions, sinus tachycardia, atrial tachycardia, atrial fibrillation
—>more severe in men, elderly, pts with pre-existing heart disease
Can lead to cardiomyopathy
Atrial fibrillation may cause heart failure
Can cardiopulmonary manifestations of thyrotoxicosis be reversed?
Yes, often partially or fully reversible with thyrotoxicosis treatment
When do pregnant women often have remission of graves?
Late second trimester
What are pregnancy complications of untreated thyrotoxicosis?
Maternal: preeclampsia-eclampsia, maternal heart failure, thyroid storm
Fetal: miscarriage, preterm delivery, placental abruption, neonatal thyrotoxicosis
Why would a pregnant patient see an improvement in Grave’s disease during the course of her pregnancy?
Pregnancy causes inhibition of immune system so fetus is not rejected and grave’s disease is due to immunoglobulins
Divya is a 37-year-old female who was just diagnosed with primary hyperthyroidism. She has not received any clinical interventions to treat her hormone status. What would we expect her T4, T3, TSH, and TRH level to be?
T4: increased
T3: increased
TSH: decreased
TRH: decreased
How are patients with suspected thyrotoxicosis screened?
Serum TSH (+/- FT4)
What lab abnormalities other than T4, T3, TSH, TRH can be seen with thyrotoxicosis?
Hypercalcemia, increased alkaline phosphatase, anemia, decreased granulocytes
(Thyroid hormones cause bone resorption —> hypercalcemia, alkaline phosphatase is an enzyme involved in bone, anemia due to bone marrow depression and altered iron metabolism, same with granulocytes)
If a patient has Grave’s disease, which immune globulin is most likely to be responsible?
TSI followed by anti-TPO, anti-Tg
(TSI=thyroid-stimulating Ig)
If thyroiditis what abnormalities are often seen on labs?
Increased ESR, negative anti thyroid antibodies
If thyrotoxicosis factitia, what is often seen on labs?
Low serum thyroglobulin levels
(They took excess thyroid medication, so thyroid precursors will be low)
What is radioactive iodine uptake/scanning used for? Why is it helpful?
Thyrotoxicosis analysis; helps determine etiology by measuring thyroid metabolism by radioactive tracer iodine uptake
If there is elevated radioactive iodine uptake, what condition may be present?
Graves’ disease, toxic solitary nodule, toxic multinodular goiter, type I amiodarone thyrotoxicosis
If there is decreased radioactive iodine uptake, what conditions may be present?
Thyroiditis, iodine-induced thyrotoxicosis, type II amiodarone thyrotoxicosis
Who should not be given radioactive iodine uptake/scanning?
Pregnant women, or if you suspect cancer (does not differentiate)
Why would you order thyroid ultrasound?
Evaluation of thyromegaly, nodules
This diagnostic imaging test can identify areas of increased blood flow and supplement ultrasound
Color flow Doppler sonography
What are opthalmic complications of thyrotoxicosis?
Severe opthalmopathy can cause extraocular muscle entrapment, diplopia, optic nerve compression, and corneal drying with incomplete lid closure
Ocular myasthenia gravis is also associated
How are opthalmic complications of thyrotoxicosis treated?
Steroid therapy or, if severe, radiation or surgery
What are cardiac complications of thyrotoxicosis?
Arrhythmias, heart failure
May need treated with cardiac medications (BBs, digoxin, anticoagulation)
What are cardiac complications of thyrotoxicosis?
Dyspnea, pulmonary hypertension
How can thyrotoxicosis impact electrolytes?
Calcium: hypercalcemia, osteoporosis, nephron alcanos is
Hypokalemic periodic paralysis: symmetric flaccid paralysis after IV dextrose, oral carbs, or vigorous exercise- in Asian or American Indian men
Severe, life-threatening thyrotoxicosis
Thyroid storm
What can trigger thyroid storm?
Illness, RAI administration, thyroid surgery
How does thyroid storm manifest?
(Similar to thyrotoxicosis, but worse)
Marked delirium
Severe tachycardia
Vomiting and diarrhea
Dehydration
Very high fever (from high metabolic activity)
How is thyroid storm treated?
Thiourea drug
Iodinated contrast agent
Beta blocker
Hydrocortisone
Avoidance of aspirin therapy (NSAIDs bind to proteins in blood)
Definitive treatment: radioactive iodine or surgery
What thiourea drugs can be used for treatment of thyroid storm and what is their mechanism of action?
Methimazole or PTU: inhibit oxidation of iodine, prohibiting thyroid hormone formation
What iodinated contrast agents can be used for treatment of thyroid storm? What is their mechanism of action?
Ipodate sodium or iopanoic acid: inhibit peripheral conversion of t4 to T3
What beta blockers can be used for treatment of thyroid storm and what is their function?
Propranolol or atenolol: relives symptoms of tachycardia, tremor, anxiety
Normal serum FT4 and T3 with low TSH
Subclinical hyperthyroidism
What are manifestations of subclinical hyperthyroidism?
Asymptomatic or mild hyperthyroid s/s, higher risk of complications like osteopenia/osteoporosis and cardiac arrhythmias
How is subclinical hyperthyroidism treated?
Observation if no s/s
Evaluation and treatment of cause: if TSH <.1 mlU/L, if symptomatic, or if high risk for complications
What is the prognosis of subclinical hyperthyroidism?
1-2% per year progress to symptomatic thyrotoxicosis
If multinodular goiter: 5% per year progress
Excess ingestion of which food product can cause hyperthyroidism? (Red meat, chamomile tea, kelp supplements, omega-3 fatty acids)
Kelp supplements (high iodine content)
While useful to evaluate thyroid disease, thyroid ultrasonography is limited in that it cannot…
(Assess metabolic activity of a thyroid mass, distinguish a solid mass from a cystic mass, assess blood flow to the thyroid gland, evaluate smooth versus poorly defined mass margins)
Assess metabolic activity of a thyroid mass
Untreated hyperthyroidism could eventually lead to all of the following complications, except…
(Osteoporosis, peripheral edema, edema, atrial fibrillation)
Peripheral edema, edema
How is Grave’s disease treated?
Beta blockers
Iodinated contrast agents
Thiourea drugs
What beta blockers can be given for grave’s disease and why?
Propranolol, atenolol: improve tachycardia, palpitations, anxiety, tremor, etc
Often given initially for s/s until anti thyroid therapies have chance to work
What iodinated contrast agents are given for Grave’s disease and why?
Iopanoic acid, ipodate sodium: block conversion of T4 to T3
Given to severely symptomatic thyrotoxic patients but efficacy wanes over time
What thiourea drugs can be given for Grave’s disease and what is their mechanism of action?
Methimazole, propylthiouracil: inhibit production of thyroid hormone without permanent damage to thyroid
Which patients are thiourea drugs particularly useful in?
Mild cases, elderly, young adults, patients who cannot have more definitive treatments, to prepare for RAI or surgery
What side effects are associated with thiourea drugs?
Agranulocytosis and pancytopenia
Which thiourea drug is preferred for most patients? Which one is preferred if first trimester or breastfeeding?
Methimazole: preferred in most patients
Propylthiouracil (PTU): preferred if first trimester or breastfeeding
What is the mechanism of action of Methimazole?
Inhibits organification of iodine, blocking formation of thyroid hormone
What are indications for Methimazole?
General hyperthyroidism, hyperthyroidism due to Graves’ disease
Methimazole carries a greater risk of ______ and _____ than PTU
Teratogenicity, goes more into breast milk
What are side effects of Methimazole?
Derm: pruritis, rash urticaria
MSK: joint pain
GI: abnormal taste, N/V, hepatotoxicity (less than PTU)
Heme: agranulocytosis (greatest risk in first 2-3 months of tx)
What are contraindications of Methimazole?
Hypersensitivity to prescription
What should you monitor while a patient is on Methimazole?
Thyroid labs, CBC, liver functions tests
What is the mechanism of action of propylthiouracil?
Inhibits organification of iodine, blocking formation of thyroid hormone; also decreases peripheral tissue conversion of T4 to T3
What are indications of propylthiouracil?
Hyperthyroidism
Propylthiouracil has greater risk of _____ than Methimazole and has a _______
Hepatotoxicity, black box warning
What are side effects of propylthiouracil?
Derm: pruritis, rash, urticaria
MSK: joint pain
GI: abnormal taste, N/V, hepatotoxicity (higher risk than methimazole)
Heme: agranulocytosis (highest risk in first 2-3 months of treatment)
Reproductive: lower risk of teratogenicity and breast milk transmission
What are contraindications of propylthiouracil?
Hypersensitivity, in Canada breastfeeding is also CI (allowed in US)