Thyroid Flashcards
what is hyperthyroidism
A condition caused by the effects of too much thyroid hormone.
Excess synthesis and secretion of thyroid hormone by the thyroid gland, also known as thyrotoxicosis.
Most common of thyrotoxicosis:
• diffuse toxic goiter (Graves disease, ~50-60%)
• toxic multinodular goiter (Plummer disease, 15-20%)
• toxic adenoma (3-5%).
Signs and symptoms
Constitutional
– Sweating, warm/moist skin, muscle weakness, wt loss, increased appetite
CV
- Increased heart rate, high-output CHF, cardiomegaly, pulm/periph edema, MVP, Afib, heart block, dysrhythmias
Pulmonary
- Increased RR, increased min vent
Neuro
- Anxiety, confusion, tremor, seizures
GI
- Secretory diarrhoea, increased alk phos
Heme
- Decreased white blood cells, decreased Hb, decreased Plts
Renal
- Decreased potassium excretion, increased sodium excretion
Osular
- Exophthalamus
Derm
- Vitiligo, hyper pigmentation
Psych
- Emotional instability, insomnia
Thyroid nodules
Malignant • Papillary carcinoma • Follicular carcinoma • Hurthle cell tumor • Medullary Thyroid Carcinoma • Anaplastic Carcinoma • Lymphoma of thyroid
Benign
• Benign thyroid cysts (degenerated nodules)
• Colloid nodules
• Multinodular goiter
Differential diagnosis of a solitary thyroid nodule
Colloid Nodule Adenoma Cyst Focal Thyroiditis Thyroid Carcinoma Hemithyroidectomy
The thyroid nodule
• Benign adenomas or cysts account for approximately 90% of detected thyroid nodules.
Causes of thyroid nodularity
Benign
• Follicular Adenomas
• Multinodular goiter (colloid adenoma) • Hashimoto’s thyroiditis
• Cysts (colloid, simple, hemorrhagic)
Malignant
• Papillary Carcinoma
• Follicular Carcinoma
• Medullary Carcinoma
• Anaplastic and poorly differentiated carcinoma
• Primary lymphoma of the thyroid
• Metastatic carcinoma (especially breast and renal cell carcinoma)
Risk of malignancy in thyroid nodules
Hot nodules 1 to 4 % risk malignancy
Low 123I uptake within single palpable cold nodule: 10 to 25% chance of malignancy
Low 123I uptake within single palpable cold nodule if multiple nodules demonstrated: 1 to 3% risk of malignancy
Cold lesions nodules up to 80% cold lesions benign
Risk cancer in nodules with increased 99mTc uptake approximately 29% (compared to 4% with increased uptake 123I)
Risk factors for thyroid carcinoma
- Age (<20 or >60)
- Male sex
- Prior radiation
- Family history
- Family history of medullary carcinoma, pheochromocytoma, hyperparathyroidism (MEN syndrome)
- Respiratory distress, voice changes, hoarseness, cough, dysphagia
- Rapid growth of lesion
- Ipsilateral lymph node enlargement
- Long-standing goitre
Cold nodules
- Thyroiditis
- Fibrosis
- Cyst
- Non-functioning Adenoma
- Multinodular Goiter
- Malignancy
Hot nodules
Functioning Adenoma Thyroiditis
Multinodular goiter
US thyroid imaging
Ultrasound examination of the nodule is helpful for determining the nature of the nodule, whether cystic, solid, or mixed.
In addition, knowing the exact location of the nodule and the size can be helpful when planning FNAB.
US can also be used to exclude the presence of other nodules, which indicates a multinodular disease process.
- Facilitate fine needle aspiration biopsy of a nodule
- Assess the comparative size of nodules, lymph nodes, or goiters in patients who are under observation or therapy
- Evaluate for recurrence of a thyroid mass after surgery
Fine needle aspiration biopsy
• Most important step in the diagnostic evaluation of thyroid nodules, exception would include hyperthyroidism where scintigraphy should be performed first or highly suspicious exams warranting immediate surgery.
• Mean sensitivity higher than 80% and specificity higher than 90%.
• Can categorize tissue into the following diagnostic categories: malignant, benign, thyroiditis, follicular neoplasm, suspicious, or nondiagnostic
• Cost Effective – some studies estimate that it reduces cost by 25 % and reduce the need for diagnostic
thyroidectomy by 20-50%.
Limitations:
• Hypocellular aspirates may be observed in cystic nodules, or they may be related to biopsy technique.
• The absence of malignant cells in an acellular or hypocellular specimen does not exclude malignancy.
• Inability to reliably distinguish a benign follicular neoplasm from a malignant neoplasm.
• Aspirates may be required from multiple sites of
the nodule to improve sampling.
CT thyroid imaging
CT is useful in evaluating
• lymphadenopathy
• local tumor extension
• extension into the mediastinum or retro- tracheal region
MRI thyroid imaging
MRI is not as sensitive as US in depicting intrathyroid lesions.
MRI is helpful in the evaluation of local extension of thyroid neoplasms or the spread of disease into the mediastinum or retro-tracheal region
Mostly incidental
NM thyroid imaging
To determine the size, shape and position of the thyroid gland
• Pertechnetate (99mTcO4) scan • Iodine-123 scan
To assess thyroid uptake function
Radionuclide scanning
• Used to identify whether a nodule is functioning.
• Functioning nodules are nearly always benign
• Approximately 90 percent of nodules are nonfunctioning
• 5 percent of nonfunctioning nodules are malignant
• Thus, in the patient with a suppressed level of serum thyrotropin, radionuclide confirmation of a functioning nodule may obviate the need for biopsy.
