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What is the most common method of detecting thyroid nodules?
What is the most common method of detecting thyroid nodules?
What represents the ultrasound pattern most indicative of thyroid malignancy?
What represents the ultrasound pattern most indicative of thyroid malignancy?
Which factor is associated with a higher risk of developing thyroid nodules?
Which factor is associated with a higher risk of developing thyroid nodules?
Which of the following is the preferred method for obtaining tissue from a thyroid nodule?
Which of the following is the preferred method for obtaining tissue from a thyroid nodule?
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What is the percentage of ultrasound-detected thyroid nodules that are malignant?
What is the percentage of ultrasound-detected thyroid nodules that are malignant?
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What is the primary output hormone of the thyroid gland?
What is the primary output hormone of the thyroid gland?
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Which metabolic process is stimulated by low levels of thyroid hormones?
Which metabolic process is stimulated by low levels of thyroid hormones?
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What role does T3 primarily serve in the body?
What role does T3 primarily serve in the body?
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How does excessive levels of thyroid hormones affect protein metabolism?
How does excessive levels of thyroid hormones affect protein metabolism?
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What is the effect of calcitonin produced by the thyroid gland?
What is the effect of calcitonin produced by the thyroid gland?
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What is the primary mechanism by which T3 is produced?
What is the primary mechanism by which T3 is produced?
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What is the main consequence of excess thyroid hormones on lipid metabolism?
What is the main consequence of excess thyroid hormones on lipid metabolism?
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What does TSH primarily stimulate?
What does TSH primarily stimulate?
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What is the primary autoimmune condition that causes hypothyroidism in North America?
What is the primary autoimmune condition that causes hypothyroidism in North America?
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Which of the following is a common clinical manifestation of severe hypothyroidism (myxedema)?
Which of the following is a common clinical manifestation of severe hypothyroidism (myxedema)?
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Which is NOT a common associated condition with Hashimoto’s thyroiditis?
Which is NOT a common associated condition with Hashimoto’s thyroiditis?
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Which laboratory findings would typically be seen in a patient with primary hypothyroidism?
Which laboratory findings would typically be seen in a patient with primary hypothyroidism?
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What medication is primarily used for the treatment of primary hypothyroidism?
What medication is primarily used for the treatment of primary hypothyroidism?
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In a patient with hypothyroidism, what is the recommended approach for dosing Levothyroxine in elderly patients?
In a patient with hypothyroidism, what is the recommended approach for dosing Levothyroxine in elderly patients?
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How often should TSH levels be checked after starting treatment for hypothyroidism?
How often should TSH levels be checked after starting treatment for hypothyroidism?
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What is a potential risk when a patient with hypothyroidism starts to experience hyperthyroidism during treatment?
What is a potential risk when a patient with hypothyroidism starts to experience hyperthyroidism during treatment?
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Which of the following antibodies is commonly tested for in the diagnosis of Hashimoto's thyroiditis?
Which of the following antibodies is commonly tested for in the diagnosis of Hashimoto's thyroiditis?
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Which lifestyle factor is known to increase the risk of developing Hashimoto’s thyroiditis?
Which lifestyle factor is known to increase the risk of developing Hashimoto’s thyroiditis?
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What is the most common clinical presentation of thyroid cancer in women aged 30-40?
What is the most common clinical presentation of thyroid cancer in women aged 30-40?
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Which thyroid cancer type is characterized by lymphatic invasion and a high 10-year survival rate?
Which thyroid cancer type is characterized by lymphatic invasion and a high 10-year survival rate?
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What typical diagnostic evaluation is used to determine the size and location of thyroid masses?
What typical diagnostic evaluation is used to determine the size and location of thyroid masses?
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Which treatment is usually involved in managing differentiated thyroid cancers?
Which treatment is usually involved in managing differentiated thyroid cancers?
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Which factor is NOT considered a poor prognostic feature for Follicular Thyroid Carcinoma?
Which factor is NOT considered a poor prognostic feature for Follicular Thyroid Carcinoma?
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What is the characteristic feature of Medullary Thyroid Carcinoma related to genetic testing?
What is the characteristic feature of Medullary Thyroid Carcinoma related to genetic testing?
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Which subtype of thyroiditis is primarily caused by autoimmune factors?
Which subtype of thyroiditis is primarily caused by autoimmune factors?
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What is a common clinical course associated with Painless Lymphocytic Thyroiditis?
What is a common clinical course associated with Painless Lymphocytic Thyroiditis?
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What is the primary cause of Subacute Granulomatous Thyroiditis?
What is the primary cause of Subacute Granulomatous Thyroiditis?
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Which thyroid cancer type is associated with the poorest prognosis?
Which thyroid cancer type is associated with the poorest prognosis?
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What is the most common cause of hyperthyroidism?
What is the most common cause of hyperthyroidism?
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Which of the following is NOT a symptom uniquely associated with Graves disease?
Which of the following is NOT a symptom uniquely associated with Graves disease?
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What diagnostic evaluation finding is typically present in Graves disease?
What diagnostic evaluation finding is typically present in Graves disease?
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Which of the following is an advantage of using thionamides for treating hyperthyroidism?
Which of the following is an advantage of using thionamides for treating hyperthyroidism?
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What is a common examination finding associated with a nontoxic multinodular goiter?
What is a common examination finding associated with a nontoxic multinodular goiter?
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Which treatment option is considered definitive for toxic multinodular goiter?
Which treatment option is considered definitive for toxic multinodular goiter?
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What type of nodules might indicate the need for fine-needle aspiration (FNA) in assessment of thyroid nodules?
What type of nodules might indicate the need for fine-needle aspiration (FNA) in assessment of thyroid nodules?
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What is one of the major side effects of thionamides?
What is one of the major side effects of thionamides?
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In the context of thyroid nodules, what does an increase in urinary iodine levels suggest?
In the context of thyroid nodules, what does an increase in urinary iodine levels suggest?
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What is considered a common presenting symptom of toxic multinodular goiter?
What is considered a common presenting symptom of toxic multinodular goiter?
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What does the presence of TSH receptor antibodies indicate?
What does the presence of TSH receptor antibodies indicate?
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Which demographic is more likely to present with diffuse nontoxic goiter?
Which demographic is more likely to present with diffuse nontoxic goiter?
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Which form of thyroiditis is characterized by transient inflammation?
Which form of thyroiditis is characterized by transient inflammation?
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What does a thyroid scan showing heterogeneous uptake signify?
What does a thyroid scan showing heterogeneous uptake signify?
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Study Notes
Thyroid Disorders
- Thyroid disorders are characterized by either deficiency or excess production of thyroid hormones.
- Hypothyroidism is characterized by reduced thyroid hormone production.
- Hyperthyroidism is characterized by increased thyroid hormone production.
- Thyroid function tests (TFTs) are used to assess thyroid function.
Thyroid Gland Hormonal Pathway
- The hypothalamus releases thyrotropin-releasing hormone (TRH).
- TRH stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH).
- TSH stimulates the thyroid gland to produce and release triiodothyronine (T3) and thyroxine (T4).
- T3 and T4 are the primary thyroid hormones responsible for regulating metabolism, body temperature, and heart rate.
Metabolic Effects of Thyroid Hormones
- Thyroid hormones (T3 and T4) play a crucial role in regulating metabolism.
- They influence protein, carbohydrate, and lipid metabolism.
- Excess levels of T3 and T4 can lead to protein degradation, while low levels stimulate protein synthesis.
- Increased levels of T3 and T4 stimulate glycogenolysis and gluconeogenesis, while low levels promote glycogen synthesis and glucose utilization.
- Thyroid hormones increase lipolysis and fatty acid oxidation, leading to a net decrease in cholesterol.
Thyroid Functions
- Thyroid hormones increase basal metabolic rate.
- Thyroid hormones control body temperature.
- Thyroid hormones affect protein synthesis.
- Thyroid hormones play a role in long bone growth.
- Thyroid hormones regulate protein, fat, and carbohydrate metabolism.
- Thyroid gland produces calcitonin, which regulates calcium levels in the body.
T3 (Triiodothyronine)
- T3 represents about 20% of thyroid hormone output.
- It has a shorter serum half-life.
- Most T3 is produced from T4 through de-iodination.
- Cells have a higher affinity for T3 compared to T4.
T4 (Thyroxine)
- T4 is the primary thyroid hormone output, comprising about 80%.
- It has a longer serum half-life compared to T3.
- T4 is less physiologically active at the cellular level than T3.
Thyroid Function Tests (TFTs)
- TFTs include measurements of TSH, total T3, and T3 uptake.
- TSH is produced by the anterior pituitary gland.
- Total T3 includes both bound and free T3.
- T3 uptake measures unoccupied thyroid-binding globulin (TBG), inversely related to the amount of TBG bound to thyroid hormones.
- TFTs are used to diagnose and monitor thyroid disorders.
Primary Hypothyroidism - Clinical Presentation
- Primary hypothyroidism usually has an insidious onset.
- Patients may only become aware of symptoms when euthyroidism is restored.
- Patients with Hashimoto's thyroiditis may have goiter but lack significant symptoms.
Hypothyroidism - Differential Diagnosis
- Differential diagnosis for hypothyroidism includes Hashimoto's thyroiditis, subacute thyroiditis, iodine deficiency, post-ablative hypothyroidism, post-surgical hypothyroidism, and medication-induced hypothyroidism.
Thyroiditis: Hashimoto’s Disease
- Hashimoto's thyroiditis is an autoimmune disease that primarily affects the thyroid gland.
- It is characterized by immune system attacks on follicular cells.
- Autoantibodies are produced against thyroid components, leading to inflammation and eventual destruction of the thyroid gland.
Hashimoto’s Thyroiditis
- Hashimoto's thyroiditis is the most common cause of hypothyroidism in North America.
- It is more prevalent in areas with high dietary iodine intake.
- Smoking increases the risk of Hashimoto's thyroiditis.
- Common symptoms include goiter, depression, and chronic fatigue.
- Hashimoto's thyroiditis can co-occur with other diseases, such as IBS, celiac disease, Turner's syndrome, hepatitis C, and adrenal insufficiency.
- Diagnosis is confirmed by elevated TSH levels, low thyroid hormone levels, and presence of anti-thyroid peroxidase antibodies.
- In the initial stages, there may be a transient phase of hyperthyroidism due to the release of stored thyroid hormones.
Severe Hypothyroidism - Myxedema
- Myxedema is a severe form of hypothyroidism in adults.
- It is characterized by dry skin, swelling around the lips and nose, mental deterioration, and a subnormal basal metabolic rate.
Myxedema
- Myxedema is characterized by firm inelastic edema, dry skin and hair, and loss of mental and physical vigor.
- Myxedema coma is a life-threatening emergency associated with severe hypothyroidism.
Primary Hypothyroidism – Diagnostic Evaluation
- Primary hypothyroidism is diagnosed through elevated TSH levels and low free T4 levels.
- Anti-thyroid antibodies are elevated in autoimmune thyroiditis.
- Many hypothyroid patients have high serum cholesterol or triglyceride levels.
Primary Hypothyroidism – Treatment & Monitoring
- Treatment involves levothyroxine (Synthroid) replacement therapy.
- Dosing is individualized, starting low and gradually increasing until TSH levels are normalized.
- Treatment is typically lifelong.
- Alternative treatments may include combination therapy with T3 and T4.
HYPERTHYROIDISM
- Hyperthyroidism is characterized by overproduction of thyroid hormones, leading to increased T3 and T4 levels.
- Common causes include Graves' disease, painless lymphocytic thyroiditis, subacute thyroiditis, toxic thyroid adenoma, and toxic multinodular goiter (MNG).
Graves Disease
- Graves' disease is the most common cause of hyperthyroidism.
- It is an autoimmune disease characterized by TSH receptor antibodies that bind and activate the TSH receptor on the thyroid gland.
- Graves' disease has unique features:
- Orbitopathy (eye problems): Upper eyelid retraction, lid lag, swelling, erythema, conjunctivitis, and bulging eyes (exophthalmos).
- Acropachy (finger and toe swelling): Soft-tissue swelling of the hands and clubbing of the fingers.
- Dermopathy (pretibial myxedema): Skin lesions or areas of non-pitting edema on the anterior or lateral aspects of the legs or in sites of old or recent trauma.
Graves Disease
- Graves’ disease is characterized by:
- Ophthalmopathy: lid retraction, periorbital edema, conjunctival injection, & exophthalmos.
- Thyroid dermopathy over the lateral aspects of the shins.
- Thyroid acropachy.
Graves Disease: Diagnostic Evaluation
- Graves’ disease is diagnosed through low TSH levels, elevated free T3 and T4 levels, and presence of TSH receptor antibodies.
- Thyroid radionuclide scan (technetium 99) shows increased uptake of iodine.
Graves Disease – Treatment & Monitoring
- Treatment involves:
- Beta-blockers: Propranolol is used for symptomatic relief of tachycardia, tremor, diaphoresis, and anxiety.
- Antithyroid drugs: Methimazole and propylthiouracil inhibit thyroid hormone synthesis.
- Radioactive iodine (I-131): Ablates thyroid tissue.
- Thyroidectomy: Total or subtotal removal of the thyroid gland.
Graves Disease: Treatment and Monitoring
- Thionamides (anti-thyroid) drugs offer advantages:
- Possible permanent remission (30-50%).
- Avoiding permanent hypothyroidism.
- Thionamides have disadvantages:
- Minor side effects: rash, hives, GI symptoms, arthralgias.
- Major side effect: Agranulocytosis (rare but serious).
Thyromegaly & Goiter: Management
- Management of thyromegaly and goiter depends on the underlying cause.
- Thyroid enlargement during physical examination should prompt further evaluation to identify the cause.
Diffuse Nontoxic (Simple) Goiter
- Common in women due to higher prevalence of autoimmune diseases and increased iodine demands during pregnancy.
- Most patients are asymptomatic if thyroid function is preserved.
- Physical examination reveals a symmetrically enlarged, non-tender, and soft thyroid gland without palpable nodules.
- Marked enlargement can lead to compression of adjacent structures.
Diffuse Nontoxic (Simple) Goiter
- Diagnostic evaluation includes:
- TFTs: Normal or slightly elevated TSH, low total T4, with normal T3.
- TPO antibodies: To identify patients at increased risk of autoimmune thyroid disease.
- Low urinary iodine levels: Indicates iodine deficiency.
Nontoxic Multinodular Goiter
- Characterized by multiple nodules of varying sizes.
- May have symptoms from compression of adjacent tissues.
- Pemberton’s sign suggests pressure in the thoracic inlet.
- Tracheal deviation can lead to inspiratory stridor.
Nontoxic Multinodular Goiter
- Diagnostic evaluation:
- TSH level: Usually normal, but should be measured to exclude hyper- or hypothyroidism.
- PFTs: Assess the functional effects of tracheal compression.
- CT or MRI: Evaluate goiter anatomy and substernal extension.
- Barium swallow: Reveal esophageal compression.
- Ultrasonography: To identify nodules for biopsy.
Nontoxic Multinodular Goiter
- Treatment:
- Most cases can be managed conservatively.
- Avoid iodine-containing substances to avoid excess thyroid hormone production.
- Glucocorticoids or surgery may be needed for acute compression.
- Radioiodine may be used when surgery is contraindicated.
Toxic Multinodular Goiter
- Similar pathogenesis to nontoxic MNG but with functional autonomy.
- Clinical presentation includes subclinical or overt hyperthyroidism, often in older patients, with symptoms of atrial fibrillation, palpitations, tachycardia, nervousness, tremor, and weight loss.
- May have recent exposure to iodine triggering or exacerbating thyrotoxicosis.
Toxic Multinodular Goiter
- Diagnostic evaluation includes:
- Low TSH levels.
- Normal or slightly increased T4 levels.
- Elevated T3 levels.
- Heterogeneous uptake on thyroid scan.
- US to assess for cold nodules.
- FNA if cold nodule is present and cytology is indeterminate or suspicious.
Toxic Multinodular Goiter
- Treatment options:
- Antithyroid drugs: Normalize thyroid function, particularly useful in elderly or patients with limited lifespan.
- Radioiodine: Treats areas of autonomy and decreases goiter mass.
- Surgery: Definitive treatment for underlying thyrotoxicosis and goiter.
THYROID NODULE
Thyroid Neoplasia
- Neoplasm: A new and abnormal growth of tissue.
- Tumor: A neoplastic mass.
- Benign: Not malignant, not cancer.
- Malignant: Cancer → Invasive, uncontrolled, metastatic.
- Thyroid adenoma: A benign tumor of the thyroid gland.
- Thyroid nodule: A thyroid mass, cystic or solid.
- Could be benign or malignant.
Thyroid Nodules
- Incidence: Female: Male ratio is 3:1.
- Detection: 40% by self, 30% through physician examination, 30% incidentally found on imaging.
- Malignancy: ~10% of ultrasound-detected nodules are malignant.
Thyroid Nodules
- Enlargement (goiter) can be diffuse or irregular (nodular).
- Nodular goiter is common in areas with iodine deficiency.
- Past head/neck irradiation increases thyroid nodule risk, including thyroid cancer.
- Palpable solitary nodules are often benign adenomas or colloid nodules.
- Functioning adenomas can lead to thyrotoxicosis (toxic adenoma).
- Other thyroid pathology includes primary or metastatic neoplasms, thyroiditis, infections, and cysts.
Evaluation of Thyroid Mass or Enlargement
-
Imaging:
- Ultrasound of Thyroid: First-line choice, determining nodule number and size.
- Thyroid Scan (radionuclide study): Helpful if TSH is low, to identify "hot nodules" and differentiate between Graves' disease and thyroiditis.
- CT, MRI: Seldom used due to expense and US accuracy.
-
Obtaining Tissue:
- FNA (fine needle aspiration): Preferred method for biopsy.
- Open biopsy: If FNA is inconclusive.
Thyroid Nodule US
- Sonographic patterns of thyroid nodules can help with diagnosis:
- High suspicion for malignancy: Hypoechoic solid nodule with irregular borders and microcalcifications.
- Very low suspicion for malignancy: Spongiform nodule with microcystic areas comprising over 50% of nodule volume.### Thyroid Cancer
- Most commonly, thyroid cancer is an asymptomatic thyroid nodule found on palpation or ultrasound in females between 30-40 years of age.
- May present with painless swelling.
- Thyroid function tests (TFTs) are usually normal, but a fine needle aspiration (FNA) biopsy is needed for a positive diagnosis.
- Imaging studies like ultrasound, radioisotope scans, and chest x-rays (CXR), are used to determine the size and location of the masses.
- Most thyroid cancers are differentiated and secrete thyroglobulin which can be used as a marker following thyroidectomy.
- The most common treatment is a total thyroidectomy followed by radioactive iodine ablation and TSH suppression with high dose levothyroxine.
- Treatment for less common subtypes like medullary, lymphoma, and anaplastic, is tailored to the specific type.
Thyroid Cancer Histological Types
- Papillary thyroid cancer is the most common type, accounting for 80-85% of cases. It is usually well differentiated and multifocal, often invading lymph nodes. More than 90% of patients survive 10 years with a low risk of recurrence or metastasis.
- Follicular thyroid cancer represents 10% of cases. It spreads hematogenously with occasional systemic metastasis, leading to a slightly worse prognosis than papillary.
- Medullary thyroid cancer accounts for 4% of cases. It often spreads to lymph nodes early, but has an 80% 5-year survival rate.
- Anaplastic thyroid cancer is rare and aggressive with a survival of only a few months.
- Lymphoma is rare, but has a good prognosis in stage I and II, and is particularly aggressive in Stage IV, with a 1% chance of survival with distant metastases.
Follicular Carcinoma (FTC)
- Accounts for 5-10% of all thyroid cancer diagnosed in the US.
- Considered more aggressive than papillary thyroid cancer, and can secrete thyroxine leading to hyperthyroidism.
- Metastasis is common to neck lymph nodes, bone, lung, and central nervous system (CNS).
- Mortality rates are less favorable than papillary thyroid cancer.
- Poor prognostic features include distant metastases, age greater than 50, tumor size greater than 4 cm, Hürthle cell histology, and marked vascular invasion.
Medullary Thyroid Carcinoma (MTC)
- Accounts for 3-5% of thyroid cancers.
- 1/3 of cases are sporadic, presenting around 50 years of age.
- The remainder are familial, associated with multiple endocrine neoplasia (MEN) types IIA and IIB, or familial MTC without other features of MEN.
- All patients with MTC should be tested for RET mutations, as genetic counseling and testing are crucial for relatives.
- Prior to surgery for MTC, pheochromocytoma should be excluded in patients with RET mutations.
- Elevated serum calcitonin is a marker of residual or recurrent disease.
Thyroiditis
- Thyroiditis is a general term for inflammation of the thyroid gland.
Subtypes of Thyroiditis
- Chronic Lymphocytic Thyroiditis: (Hashimoto's thyroiditis, chronic autoimmune thyroiditis, lymphadenoid goiter) is autoimmune-mediated.
- Subacute Lymphocytic Thyroiditis: (postpartum thyroiditis, sporadic painless thyroiditis, silent sporadic thyroiditis) is autoimmune-mediated.
- Acute Infectious Thyroiditis: (Microbial inflammatory thyroiditis, suppurative thyroiditis, pyrogenic thyroiditis, bacterial thyroiditis) is caused by bacteria, parasites, or fungi.
- De Quervain's Thyroiditis: (subacute granulomatous thyroiditis, Giant-cell thyroiditis, painful subacute thyroiditis) is caused by a virus.
- Riedel's Thyroiditis: (Riedel's struma, Invasive fibrous thyroiditis) is of unknown cause.
Painless Lymphocytic Thyroiditis
- Autoimmune-mediated inflammation of the thyroid gland.
- Clinical course is characterized by a transient hyperthyroid phase, followed by hypothyroidism, and ultimately a euthyroid state with variable progression.
- It is more common in women, and may be associated with postpartum, lithium treatment, biologic treatments, or cytokine therapies.
- Diagnosis is based on clinical presentation and thyroid biopsy.
- Most patients remain euthyroid over time.
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Test your knowledge on thyroid nodules with this quiz. Explore methods of detection, ultrasound patterns, risk factors, and malignancy statistics related to thyroid nodules. This quiz is essential for medical students and healthcare professionals alike.
