Chapter 196 Thyroid Disorders (Initial Diagnosis and Management of Select Thyroid Disorders (no thyroid nodules or thyroid cancer)

Question 1

What is the indication for immediate referral to a thyroid surgeon?

Answer 1

Compressive symptoms

Hospitalization is indicated for respiratory compromise due to invasive tumors.

Question 2

Where is the thyroid gland located?

Answer 2

Anteriorly in the lower neck below the Adam’s apple

The thyroid is a butterfly-shaped gland.

Question 3

What are the dimensions of each thyroid lobe?

Answer 3

• Approximately 4 to 6 cm in height
• Isthmus measures 2 to 3 mm in height

The average thyroid weighs approximately 25 to 30 g.

Question 4

What are the structural units of the thyroid gland called?

Answer 4

Follicles

Each follicle is composed of epithelial cells and a follicular lumen.

Question 5

What is the primary function of follicular cells in the thyroid?

Answer 5

Thyroid hormone synthesis and secretion

Follicular cells are cuboidal in shape and derived from the endoderm.

Question 6

What substance is primarily stored in the follicular lumen?

Answer 6

Colloid

Colloid is mostly comprised of thyroglobulin.

Question 7

What regulates thyroid function?

Answer 7

Thyroid-stimulating hormone (TSH)

TSH is secreted by the anterior pituitary gland in response to TRH from the hypothalamus.

Question 8

What is the daily intake of dietary iodine sufficient for normal thyroid hormone production?

Answer 8

100 to 200 mcg

Iodine must be obtained from food, dietary supplements, and medications.

Question 9

What are the two main thyroid hormones released into circulation?

Answer 9

• Thyroxine (T4)
• Triiodothyronine (T3)

T4 comprises 90% and T3 comprises 10% of circulating thyroid hormone.

Question 10

What is the most sensitive indicator of overall thyroid function?

Answer 10

TSH

Small changes in serum T3 and T4 levels affect TSH secretion.

Question 11

What is the prevalence of hypothyroidism in women and men?

Answer 11

• 2% in women
• 0.2% in men

Prevalence increases with age.

Question 12

What condition may result from untreated hypothyroidism in adulthood?

Answer 12

Myxedema

It involves skin thickening and cardiovascular and renal manifestations.

Question 13

What is the most common cause of primary hypothyroidism?

Answer 13

Chronic autoimmune thyroiditis

This may present as atrophic or goitrous forms.

Question 14

What antibodies are associated with Hashimoto thyroiditis?

Answer 14

• Antithyroglobulin antibodies (anti-TgAbs)
• Antimicrosomal/anti-thyroid peroxidase antibodies (TPOAb)

TPOAb are found in 90% to 100% of patients with Hashimoto thyroiditis.

Question 15

What is the relationship between TPOAb and the progression of subclinical hypothyroidism?

Answer 15

Presence of TPOAb predicts progression to overt hypothyroidism

4.3% per year with TPO versus 2.6% without elevated TPO titers.

Question 16

What is the typical age range for the onset of autoimmune thyroid diseases?

Answer 16

More common in women than men

Occurs 5 to 10 times more often in women.

Question 17

What can cause transient primary hypothyroidism during the postpartum period?

Answer 17

Postpartum thyroiditis

This may follow a brief period of hyperthyroidism.

Question 18

What drugs are known to have antithyroid action?

Answer 18

• Lithium
• Amiodarone
• Iodine
• Interferon alfa (IFN-α)
• Tyrosine kinase inhibitors
• Radiographic contrast material

These drugs may cause transient or permanent thyroid failure.

Question 19

What is the effect of large amounts of iodine consumption on thyroid hormone production?

Answer 19

Blocks thyroid hormone production

Excess oral ingestion can occur through overconsumption of iodized salt and kelp.

Question 20

What are some drugs with antithyroid action that may cause hypothyroidism?

Answer 20

• Lithium
• Amiodarone
• Iodine
• Interferon alfa (IFN-α)
• Tyrosine kinase inhibitors
• Radiographic contrast material

The drug effect may be transient or result in permanent thyroid failure.

Question 21

Excessive consumption of iodine can block what?

Answer 21

Thyroid hormone production

Overconsumption can occur through iodized salt, kelp, milk rich in iodine, iodine-containing drugs, and iodine supplementation.

Question 22

Who is more susceptible to hypothyroidism when taking iodine or iodine-containing drugs?

Answer 22

• Elderly patients
• Those with underlying chronic autoimmune thyroiditis

This is particularly true in iodine-sufficient geographic areas.

Question 23

What are pituitary causes of hypothyroidism usually associated with?

Answer 23

Other signs of pituitary hormone insufficiency

Patients with a history of pituitary disease or tumor may be at risk for thyroid hyposecretion.

Question 24

What are the cardiac and metabolic consequences of thyroid hormone deficiency?

Answer 24

• Impaired myocardial contractility
• Cardiomegaly
• Impaired lipid metabolism
• Accelerated atherosclerosis
• Hypertension
• Depressed ventilatory drive
• Fatigue
• Impaired energy use
• Weight gain

These effects relate primarily to a hypometabolic state and myxedematous involvement of body tissues.

Question 25

What are some **musculoskeletal effects** of hypothyroidism?

Answer 25

* Increased volume of muscle * Slowness of contraction * Myopathic disorders * Connective tissue thickening * Entrapment neuropathies (e.g., carpal tunnel syndrome) ## Footnote In children, delayed skeletal maturation may cause growth retardation.

Question 26

What is the most common **presenting symptom** of hypothyroidism?

Answer 26

Fatigue ## Footnote Other symptoms may include increased sensitivity to cold, weight gain, hoarseness, and dry skin.

Question 27

What should the **physical examination** of a hypothyroid patient focus on?

Answer 27

* General appearance * Degree of energy and animation * Texture, color, and appearance of skin * Facial expression * Texture and thickness of hair * Heart rate and respiratory rate ## Footnote The thyroid gland should also be evaluated for size and nodules.

Question 28

What is the **initial diagnostic test** for hypothyroidism?

Answer 28

TSH ## Footnote If TSH is elevated, free T4 should be checked.

Question 29

What are some **additional diagnostics** for hypothyroidism?

Answer 29

* Antimicrosomal antibodies * Serum free T4 * Free T4 index * Thyroid ultrasound * Fine-needle aspiration ## Footnote Imaging studies are unnecessary for chronic autoimmune thyroiditis.

Question 30

What is **subclinical hypothyroidism** defined as?

Answer 30

Elevated TSH level with normal thyroid hormone levels ## Footnote It is often caused by autoimmune thyroiditis or inadequate T4 replacement.

Question 31

What is the recommended treatment for **hypothyroidism**?

Answer 31

Levothyroxine orally ## Footnote The dosage is adjusted based on TSH levels, typically starting at 50 mcg/day.

Question 32

What should be monitored in patients with **hypothyroidism** during pregnancy?

Answer 32

TSH levels ## Footnote Thyroid hormone requirements often increase during pregnancy.

Question 33

True or false: **Smoking** has no effect on thyroid hormone secretion.

Answer 33

FALSE ## Footnote Smoking can impair thyroid hormone secretion and action, contributing to subclinical hypothyroidism.

Question 34

When should **SH** be measured during pregnancy?

Answer 34

During the pre-natal evaluation and in every trimester thereafter ## Footnote Monitoring is crucial as thyroid hormone requirements often increase during pregnancy.

Question 35

What can untreated **hypothyroidism** adversely affect?

Answer 35

* Intrauterine fetal development * Cardiac dysfunction * Cholesterol levels * Neuropsychiatric dysfunction * Progression to overt hypothyroidism ## Footnote Untreated hypothyroidism can lead to serious complications for both the mother and fetus.

Question 36

What are the consequences of untreated **subclinical hypothyroidism**?

Answer 36

* Cardiac dysfunction * Elevated cholesterol levels * Systemic hypothyroid symptoms * Neuropsychiatric dysfunction * Progression to overt hypothyroidism ## Footnote These consequences highlight the importance of monitoring thyroid function.

Question 37

What is **myxedema coma**?

Answer 37

A hypothermic stuporous state resulting from untreated hypothyroidism ## Footnote It may be triggered by environmental or internal stressors and can lead to respiratory depression and death.

Question 38

What are the necessary treatments for **myxedema coma**?

Answer 38

* Intravenous levothyroxine * Glucocorticoid therapy * Warming for hypothermia * Ventilatory support * Treatment of renal and electrolyte imbalances ## Footnote These treatments are critical for managing the condition effectively.

Question 39

What are potential complications of **levothyroxine therapy**?

Answer 39

* Atrial fibrillation * Osteoporosis * Angina * Arrhythmias * Palpitations ## Footnote These complications may arise, especially with excessive dosing or interactions with other medications.

Question 40

What is the definition of **hyperthyroidism**?

Answer 40

A clinical syndrome caused by excess production or release of thyroid hormone ## Footnote It implies that the thyroid is the source of excess thyroid hormone.

Question 41

What is the most common cause of **hyperthyroidism**?

Answer 41

Graves disease ## Footnote This autoimmune condition has a female-to-male predominance of 7:1 and is most common in women aged 20 to 40 years.

Question 42

What are the types of **hyperthyroidism** based on TSH dependency?

Answer 42

* Primary hyperthyroidism * Secondary hyperthyroidism * Tertiary hyperthyroidism ## Footnote These classifications help in understanding the underlying causes of hyperthyroidism.

Question 43

What is **Graves disease** characterized by?

Answer 43

Autoimmune stimulation of the TSH receptor, increasing thyroid hormone production ## Footnote This condition leads to hyperthyroidism and various clinical manifestations.

Question 44

What is the **NO SPECS** mnemonic used for?

Answer 44

Describing eye changes in association with Graves disease ## Footnote It includes: No signs or symptoms, Only signs, Soft tissue swelling, Proptosis, Extraocular muscle paresis.

Question 45

What is the prevalence of **hyperthyroidism** in the United States?

Answer 45

Approximately 1.2% of the population ## Footnote Common causes include Graves disease, toxic multinodular goiter, and toxic adenoma.

Question 46

What should patients be educated about regarding **levothyroxine replacement**?

Answer 46

* It is a permanent treatment * Should be taken on an empty stomach * Do not double the next dose if missed * Annual or biannual TSH monitoring ## Footnote These guidelines help ensure effective management of thyroid hormone levels.

Question 47

What triggers **thyroid storm** and requires emergency department referral?

Answer 47

Thyrotoxic crisis and rapid atrial fibrillation ## Footnote Immediate referral is critical for managing these life-threatening conditions.

Question 48

What are the **symptoms** of **hyperthyroidism** related to the **eyes**?

Answer 48

* Dry eyes * Blurry vision ## Footnote Use the NO SPECS mnemonic for further details.

Question 49

What are the **signs** of **hyperthyroidism** related to the **neck**?

Answer 49

* Diffuse goiter in patients with Graves disease * Goiter with thyroid bruit in Graves disease ## Footnote These signs are indicative of thyroid enlargement and vascularity.

Question 50

What are the **respiratory system** symptoms of **hyperthyroidism**?

Answer 50

* Shortness of breath ## Footnote This may lead to labored respiration.

Question 51

What are the **cardiac system** symptoms of **hyperthyroidism**?

Answer 51

* Palpitation * Tachycardia * Angina ## Footnote These symptoms can lead to systolic hypertension and congestive heart failure.

Question 52

What are the **gastrointestinal system** symptoms of **hyperthyroidism**?

Answer 52

* Hyperphagia * Hyperdefecation * Weight loss * Weight gain (rare) * Anorexia in older adults ## Footnote Weight changes are common in hyperthyroid patients.

Question 53

What are the **reproductive system** symptoms of **hyperthyroidism**?

Answer 53

* Amenorrhea * Menstrual irregularities * Infertility ## Footnote These symptoms can affect fertility and menstrual cycles.

Question 54

What are the **neuromuscular system** symptoms of **hyperthyroidism**?

Answer 54

* Proximal muscle weakness * Heat intolerance * Tremor ## Footnote These symptoms can significantly impact daily activities.

Question 55

What are the **skin** symptoms of **hyperthyroidism**?

Answer 55

* Pruritus * Hyperhidrosis * Warm, moist palms * Onycholysis (brittle nails, Plummer nails) ## Footnote Skin changes can indicate hyperthyroid conditions.

Question 56

What are the **skeletal system** signs of **hyperthyroidism**?

Answer 56

* Osteoporosis * Thyroid acropachy (Graves disease) ## Footnote Osteoporosis can increase fracture risk.

Question 57

What are the **psychiatric problems** associated with **hyperthyroidism**?

Answer 57

* Anxiety * Irritability * Nervousness * Sleeplessness ## Footnote These symptoms can affect mental health and quality of life.

Question 58

What are the **diagnostics** for **hyperthyroidism**?

Answer 58

* TSH (best screening test) * T3 uptake test * Free T4 level * TRAb level ## Footnote TSH levels will be low or undetectable in primary hyperthyroidism.

Question 59

What are the **laboratory tests** for **initial diagnostics** of **hyperthyroidism**?

Answer 59

* Thyroid-stimulating hormone * Free T4 index * Total T3 * Thyrotropin receptor antibody * Baseline complete blood count * Liver function tests ## Footnote These tests help confirm hyperthyroidism before treatment.

Question 60

What are the **treatment options** for **Graves disease**?

Answer 60

* β-Blockers * Thioamides (methimazole, propylthiouracil) * Radioiodine therapy ## Footnote Treatment depends on the patient's age and severity of the disease.

Question 61

What are the **side effects** of **thioamides**?

Answer 61

* Pruritic rash * Jaundice * Arthralgias * Low risk of agranulocytosis ## Footnote Patients should be monitored for these side effects.

Question 62

What is the **initial dose** of **methimazole** for mild hyperthyroidism?

Answer 62

5 to 10 mg daily ## Footnote Higher doses are used for severe hyperthyroidism.

Question 63

What is the **initial dose** of **propylthiouracil (PTU)**?

Answer 63

50 to 100 mg three times daily ## Footnote PTU is limited to the first trimester of pregnancy due to liver failure risks.

Question 64

What are the **indications for therapy** in **subclinical hyperthyroidism**?

Answer 64

* Patients older than 60 years * Increased risk for heart disease * Osteoporosis ## Footnote Monitoring is appropriate for lower-risk patients.

Question 65

What are the **treatment options** for **subacute thyroiditis**?

Answer 65

* Symptomatic treatment with β-blockers * Anti-inflammatory agents (NSAIDs, aspirin) * Prednisone for severe pain ## Footnote Monitoring thyroid function is essential after treatment.

Question 66

What is the **treatment of choice** for patients older than 20 years with **hyperthyroidism**?

Answer 66

Radioiodine therapy ## Footnote This is indicated if thioamide therapy has failed.

Question 67

What are the **complications** of **thyroidectomy**?

Answer 67

* Hypothyroidism * Hypoparathyroidism * Hoarseness ## Footnote These complications can arise from surgical intervention.

Question 68

What is the **treatment of choice** for hyperthyroidism after β-blocker therapy?

Answer 68

Radioiodine ablation ## Footnote This treatment is preferred for conditions like Graves disease and toxic multinodular goiter.

Question 69

Define **subclinical hyperthyroidism**.

Answer 69

Suppressed TSH with normal serum T4 and T3 levels ## Footnote It may require repeated doses of 131I for treatment.

Question 70

What are the **symptoms** of untreated Graves disease?

Answer 70

* Atrial fibrillation * Osteoporosis * Weight loss despite increased appetite ## Footnote Older patients may present with apathetic hyperthyroidism.

Question 71

True or false: **Thyroid storm** is a common complication of hyperthyroidism.

Answer 71

FALSE ## Footnote Thyroid storm is rare but life-threatening, leading to systemic decompensation.

Question 72

What are the **goals of therapy** for thyroid storm?

Answer 72

* Inhibit thyroid hormone formation and release * Provide α-adrenergic blockage * Provide supportive therapy * Identify and treat precipitating illness * Initiate long-term therapy for prevention ## Footnote The incidence of thyroid storm has decreased due to advances in medical management.

Question 73

What should patients receiving **β-blockers** monitor?

Answer 73

Pulse ## Footnote Contact the healthcare provider if the pulse is less than 50 or more than 120 beats/min.

Question 74

What imaging technique is preferred for assessing the **functional status** of a thyroid nodule?

Answer 74

Thyroid scans ## Footnote Iodine isotope scans are preferred over technetium scans for distinguishing hot and cold nodules.

Question 75

What is the **normal radioactive iodine uptake (RAIU)** percentage?

Answer 75

Approximately 30% ## Footnote RAIU can be affected by recent iodine-containing compounds or high iodine/salt diets.

Question 76

What are the **characteristics** of nodules suggestive of malignancy on ultrasound?

Answer 76

* Irregular margins * Microcalcifications * Taller than wide shape * Central vascularization ## Footnote These features increase the likelihood of malignancy in thyroid nodules.

Question 77

What is the **procedure of choice** for evaluating thyroid nodules?

Answer 77

FNA biopsy ## Footnote It is safe, technically simple, and has a low rate of false-negative and false-positive results with experienced operators.

Question 78

What is the **lifetime risk** for the development of a thyroid nodule?

Answer 78

5% to 10% ## Footnote The prevalence of palpable thyroid nodules is found in 4% to 7% of the general adult population.

Question 79

What are the **malignant thyroid tumors**?

Answer 79

* Papillary carcinoma * Follicular carcinoma * Medullary carcinoma * Anaplastic carcinoma ## Footnote These tumors are characterized by capsular or vascular invasion and metastases.

Question 80

What clinical features increase the **likelihood of cancer** in thyroid nodules?

Answer 80

* History of childhood head and neck radiation * Family history of thyroid cancer * Age younger than 20 or older than 60 * Male sex ## Footnote Other factors include multiple endocrine neoplasia II and medullary thyroid cancer.

Question 81

What is the **definition** of a thyroid nodule?

Answer 81

A distinct lesion within the thyroid that is radiologically different from the rest of the thyroid ## Footnote Thyroid nodules can be solid or cystic.

Question 82

What are the **common causes** of thyroid nodules?

Answer 82

* Adenomas * Cysts * Carcinomas * Multinodular goiters * Hashimoto thyroiditis ## Footnote Less common causes include parathyroid cysts, thyroglossal cysts, and lymphomas.

Question 83

What is the **Pemberton maneuver** used for?

Answer 83

Examination of substernal extension of nodule/goiter ## Footnote Flushing of the face and respiratory distress may occur during this maneuver.

Question 84

What are the **ultrasound characteristics** predictive of benign nodules?

Answer 84

* Spongiform nodules * Simple cysts ## Footnote These characteristics suggest a lower likelihood of malignancy.

Question 85

What is the **procedure of choice** in the evaluation of thyroid nodules?

Answer 85

FNA biopsy ## Footnote FNA biopsy is safe and technically simple but requires an experienced operator and cytopathologist.

Question 86

What are the **false-negative and false-positive rates** for FNA biopsy with experienced users?

Answer 86

Less than 5% ## Footnote Cytologic results are sufficient in 85% of biopsies for diagnosis.

Question 87

What type of FNA has a lower rate of nondiagnostic and false-negative findings?

Answer 87

Ultrasound-guided FNAs ## Footnote These are preferred for better diagnostic accuracy.

Question 88

Nodule size alone is not a sufficient diagnostic predictor of malignancy and should be evaluated in conjunction with __________.

Answer 88

ultrasound characteristics of the nodule ## Footnote This evaluation is crucial for accurate diagnosis.

Question 89

According to the revised ATA thyroid cancer guidelines (2015), FNA is recommended for **high-suspicion nodules** larger than __________.

Answer 89

1 cm ## Footnote High-suspicion nodules include those with high-risk history, solid, hypoechoic, and irregular margins.

Question 90

For **intermediate-suspicion nodules**, FNA is recommended for nodules larger than __________.

Answer 90

1.5 cm ## Footnote Intermediate-suspicion nodules may have complex solid and cystic components or any suspicious ultrasound features.

Question 91

Very-low-suspicion nodules larger than __________ should also undergo FNA.

Answer 91

2 cm ## Footnote These nodules are spongiform or partially cystic without suspicious features.

Question 92

What type of nodules are likely benign and do not warrant biopsy?

Answer 92

Purely cystic nodules ## Footnote These nodules generally do not require further evaluation.

Question 93

FNA can be used to obtain material for biochemical analysis of aspirated fluid or needle washings, such as evidence of __________ in lymph node aspirate.

Answer 93

thyroglobulin ## Footnote This can confirm metastatic thyroid cancer.

Question 94

If lymphoma is suspected, what can be done during FNA?

Answer 94

Sampling for flow cytometry ## Footnote This helps in the diagnosis of lymphoma.

Question 95

Results from FNA cytologic studies are categorized based on the __________.

Answer 95

Bethesda System for Reporting Thyroid Cytopathology ## Footnote This system includes categories such as Nondiagnostic, Benign, Atypia of Undetermined Significance, and Malignant.

Question 96

What are the estimated risks of malignancy for the Bethesda category **Nondiagnostic**?

Answer 96

5% to 10% ## Footnote This is the risk associated with the Bethesda I category.

Question 97

What is the estimated risk of malignancy for the Bethesda category **Malignant**?

Answer 97

97% to 99% ## Footnote This is the highest risk category in the Bethesda System.

Question 98

What additional diagnostics may be performed if a hyper-functioning nodule is suspected?

Answer 98

Radionuclide scanning ## Footnote This is used for further evaluation in patients with multinodular goiter.

Question 99

The use of gene expression classifiers may help to avoid __________ in patients with indeterminate thyroid cytology results.

Answer 99

diagnostic surgery ## Footnote These classifiers have a high negative predictive value.

Question 100

What is the **primary laboratory test** for thyroid diagnostics?

Answer 100

Thyroid-stimulating hormone ## Footnote This test is crucial for assessing thyroid function.

Question 101

Name two **imaging techniques** used in thyroid diagnostics.

Answer 101

* Thyroid ultrasound * Radionuclide scan ## Footnote These imaging techniques help visualize thyroid nodules and assess their characteristics.

Question 102

What is the purpose of **fine-needle aspiration** in thyroid diagnostics?

Answer 102

To obtain tissue samples for cytological examination ## Footnote This procedure helps differentiate between benign and malignant thyroid nodules.

Question 103

True or false: **Molecular markers** are used in thyroid diagnostics.

Answer 103

TRUE ## Footnote Molecular markers can provide additional information about the nature of thyroid nodules.

Question 104

What is the **differential diagnosis** primarily concerned with?

Answer 104

Differentiating benign from malignant nodules ## Footnote Conditions like autoimmune thyroid diseases and parathyroid cysts must be ruled out.

Question 105

If TSH is suppressed, what is the next step in management?

Answer 105

* Check free T4 and TT3 * Order a radionuclide scan ## Footnote This helps identify autonomously functioning nodules.

Question 106

What indicates that a nodule is **rarely cancerous** on a radionuclide scan?

Answer 106

Hot nodules ## Footnote These nodules are functioning and typically do not require FNA.

Question 107

What should be done if TSH is elevated?

Answer 107

* Check free T4 * Start levothyroxine therapy ## Footnote This helps manage hypothyroidism and evaluate thyroid nodules.

Question 108

What is the recommended follow-up for **benign** cytology results?

Answer 108

* No immediate evaluation * Repeat FNA for enlarging nodules * Follow-up ultrasound in 6 to 12 months ## Footnote Enlarging nodules are defined by specific volume or diameter changes.

Question 109

What is indicated for **suspicious** or **malignant** cytology results?

Answer 109

Referral to an experienced surgeon ## Footnote Surgical options depend on the size and characteristics of the lesion.

Question 110

What is the **net mortality rate** of papillary thyroid cancer over 20 to 30 years?

Answer 110

10% to 20% ## Footnote Several factors can increase the risk of death from this cancer.

Question 111

What factors significantly increase the risk of death from thyroid cancer?

Answer 111

* Extrathyroidal invasion * Metastasis * Age older than 45 years * Tumor larger than 3 cm ## Footnote These factors are critical in assessing prognosis.

Question 112

What is the **AJCC/UICC** classification used for?

Answer 112

To stage differentiated thyroid cancer ## Footnote This classification helps predict mortality and is required for cancer registries.

Question 113

What is the goal of **thyroid hormone therapy** in thyroid cancer management?

Answer 113

Prevent hypothyroidism and TSH stimulation of thyroid cancer cells ## Footnote Suppression therapy is indicated for intermediate and high-risk disease.

Question 114

What are common **complications** of thyroid surgery?

Answer 114

* Hypoparathyroidism * Hoarseness from recurrent laryngeal nerve damage ## Footnote These complications can significantly affect patient quality of life.

Question 115

What are potential side effects of **radioiodine therapy**?

Answer 115

* Thyroid tenderness * Dry mouth * Altered taste * Dry eyes * Nausea ## Footnote Cumulative doses over 300 mCi may increase the risk of leukemia.

Question 116

What precautions should patients take after **radioiodine treatment**?

Answer 116

* No kissing or sharing utensils for 5 days * Avoid close contact with young children and pregnant women * Flush toilets twice after urinating ## Footnote These precautions help minimize radiation exposure to others.

Question 117

What is the impact of **COVID-19** on thyroid function?

Answer 117

Can lead to short-term and reversible thyroid dysfunction ## Footnote Patients with baseline thyroid disorders do not have a higher risk of contracting the virus.

Question 118

What is **nonthyroidal illness syndrome** characterized by?

Answer 118

* Hypothalamic suppression of TSH * Acute inhibition of T4 to T3 conversion * Increased rT3 levels ## Footnote This syndrome occurs during severe illness and resolves with recovery.

Question 119

What is the effect of **amiodarone** on thyroid function?

Answer 119

* Can cause hypothyroidism * Effects can be seen up to 2 to 3 years after discontinuation ## Footnote Amiodarone is an iodine-rich drug that can concentrate in the thyroid gland.

Question 120

What is the treatment for **amiodarone-associated hypothyroidism**?

Answer 120

Levothyroxine replacement therapy ## Footnote Discontinuation of amiodarone is not necessary unless it fails to correct arrhythmia.

Question 121

What is the **effective treatment** for amiodarone-associated hypothyroidism?

Answer 121

levothyroxine replacement therapy ## Footnote This treatment does not necessitate the discontinuation of amiodarone unless it fails to correct the underlying arrhythmia.

Question 122

What are the **goals of therapy** for amiodarone-associated hypothyroidism?

Answer 122

* High-normal TSH level * Mid- to low-normal free T4 level ## Footnote A larger-than-normal dose may be required due to the effect of amiodarone on T4 and T3 production.

Question 123

Approximately what percentage of patients treated with amiodarone in the U.S. become **hyperthyroid**?

Answer 123

3% ## Footnote This usually occurs between 4 months and 3 years after the start of therapy.

Question 124

What are common symptoms of **amiodarone-induced hyperthyroidism**?

Answer 124

* Redevelopment of atrial arrhythmias * Exacerbation of ischemic heart disease or congestive heart failure * Restlessness * Low-grade fever ## Footnote Symptoms may be masked due to amiodarone's β-blocking activity.

Question 125

What are the two types of mechanisms that can cause **thyrotoxicosis** in the setting of amiodarone?

Answer 125

* Overactivity of the thyroid gland (type 1) * Destructive thyroiditis (type 2) ## Footnote Most patients do not clearly fall into one or the other type.

Question 126

What should be obtained before recommending **amiodarone therapy**?

Answer 126

Baseline TFT results and thyroid antibodies ## Footnote This helps identify patients at increased risk of thyroid dysfunction.

Question 127

What is the effect of **IFN-α** on thyroid function?

Answer 127

* Induces production of thyroid antibodies * Can result in hypothyroidism, thyrotoxicosis, or biphasic thyroiditis ## Footnote Antibodies often disappear with discontinuation of IFN-α.

Question 128

What is a common thyroid dysfunction caused by **lithium**?

Answer 128

Hypothyroidism ## Footnote Lithium blocks iodine uptake and release of thyroid hormone, potentially inducing chronic autoimmune thyroiditis.

Question 129

What is the **nonthyroidal illness syndrome** characterized by?

Answer 129

* Decreased T3 * Normal or decreased T4 * Normal or decreased free T4 * Increased rT3 * Low TSH ## Footnote This syndrome reflects changes in thyroid hormone metabolism during illness.

Question 130

What percentage of patients treated with **tyrosine kinase inhibitors** develop hypothyroidism?

Answer 130

50% to 70% ## Footnote This is most commonly seen with sunitinib and is thought to be a class effect.

Question 131

What can **biotin** intake greater than 0.5 to 1.0 g daily interfere with?

Answer 131

Diagnostic assays using biotin-streptavidin technology ## Footnote High biotin intake can cause falsely low TSH and falsely elevated T4 and T3 levels.

Question 132

What is the **TSH goal** during pregnancy for women with hypothyroidism?

Answer 132

0.5 to 2.5 μIU/L ## Footnote This goal is important for normal fetal growth and development.

Question 133

What is the recommended increase in **thyroid hormone dose** for pregnant women with preexisting hypothyroidism?

Answer 133

30% ## Footnote This increase is due to estrogen-induced elevations in TBG and increased thyroid hormone requirements.

Question 134

What are the **common causes of hyperthyroidism** during pregnancy?

Answer 134

* Graves disease * hCG-mediated hyperthyroidism ## Footnote Other causes include thyroiditis, toxic adenomas, and toxic multinodular goiters.

Question 135

What is the treatment for **overt hyperthyroidism** in pregnant women?

Answer 135

Thioamides ## Footnote PTU is used in the first trimester, while methimazole is used thereafter due to its increased hepatotoxicity.

Question 136

What are the **diagnostic tests** for hyperthyroidism in pregnancy?

Answer 136

* Physical examination * TSH, free T4, TT3 * Consider TRAb levels * Consider thyroid ultrasound ## Footnote Clinical features like goiter and ophthalmopathy support a diagnosis of Graves disease.