40 Questions
What is a characteristic feature of painful thyroiditis on physical examination?
A firm and tender thyroid gland
Which of the following is NOT a precipitating factor for thyroid storm?
Pregnancy
What does an elevated 24-hour radioactive iodine uptake (RAIU) indicate?
True hyperthyroidism
In thyrotoxic Graves' disease, what is the characteristic pattern of hormone production?
Increased overall hormone production rate with a disproportionate increase in T3 relative to T4
What is the typical presentation of thyroid storm?
Fever, tachycardia, tachypnea, dehydration, delirium, coma, nausea, vomiting, and diarrhea
What is the significance of a low 24-hour radioactive iodine uptake (RAIU)?
Thyroiditis
What is the typical thyroid function test result in thyrotoxicosis?
Undetectable TSH, elevated free T4, and elevated free T3
What is the characteristic feature of painless thyroiditis?
A diffusely enlarged thyroid gland without tenderness
What is the significance of elevated T3 resin uptake?
Saturation of TBG due to elevated serum levels of T4 and T3
What is the typical presentation of thyrotoxicosis?
Fever, malaise, and weight loss
What is the primary mechanism of thyroid hormone production?
Coupling of iodinated tyrosine residues
What is the primary function of thyroid peroxidase in thyroid hormone production?
Oxidation of inorganic iodide
What is the primary cause of thyrotoxicosis in痛painful subacute thyroiditis?
Viral infection
What is the term for hyperthyroidism caused by ingestion of exogenous thyroid hormone?
Thyrotoxicosis factitia
What is the primary hormone secreted solely from the thyroid?
Thyroxine (T4)
What is the term for a condition characterized by follicles with autonomous function?
Multinodular goiter
What is the term for a severe and life-threatening form of thyrotoxicosis?
Thyroid storm
What is the term for a type of thyroiditis characterized by a painless and often self-limited course?
Painless thyroiditis
What is the primary role of thyroid-binding globulin (TBG)?
Transport of thyroid hormone
What is the primary mechanism of thyroid hormone regulation?
Feedback inhibition by thyroid hormone
What is the percentage of patients that may experience overt hypothyroidism due to amiodarone?
5% of patients
Which of the following symptoms is NOT typically associated with thyrotoxicosis?
Weight gain
What is the name of the condition characterized by hyperthyroidism, diffuse thyroid enlargement, and extrathyroidal findings of exophthalmos, pretibial myxedema, and thyroid acropachy?
Graves' Disease
What is the percentage of iodine by weight in amiodarone?
37% by weight
Which of the following physical signs is associated with thyrotoxicosis?
Warm, smooth, moist skin
What is the name of the condition characterized by severe pain in the thyroid region, which often extends to the ear?
Subacute Thyroiditis
What is the term for the leakage of thyroglobulin and thyroid hormones from the thyroid gland?
Destructive Thyroiditis
What is the term for the condition characterized by an excessive amount of thyroid hormone in the blood, but without any symptoms of hyperthyroidism?
Euthyroid Hyperthyroxinemia
What is the percentage of patients that may experience subclinical hypothyroidism due to amiodarone?
25% of patients
Which of the following is a symptom of Graves' Disease?
Gynecomastia in men
What is the significance of an increased 24 hour RAIU in a non-pregnant or non-lactating patient?
The thyroid gland is inappropriately using iodine to produce more thyroid hormone when the patient is thyrotoxic
What is the diagnosis of a patient with autonomous function, normal TSH levels, and normal T4 levels, but elevated T3 levels?
T3 toxicosis
What is the characteristic of thyroid scans in patients with multinodular goiters?
Patchy areas of autonomously functioning thyroid tissue
What is the diagnostic criterion for TSH induced hyperthyroidism?
Elevated TSH levels, diffuse thyroid gland enlargement, and elevated free thyroid hormone levels
What is the significance of a 'normal' or elevated TSH level in a thyrotoxic patient?
Inappropriate production of TSH
What is the diagnostic criterion for TSH secreting pituitary adenomas?
Lack of TSH response to TRH stimulation, inappropriate TSH levels, elevated TSH α subunit levels, and radiologic imaging
What is the characteristic of thyroid function tests in patients with subacute thyroiditis?
Triphasic course with initially elevated T4 levels, followed by a decrease, and then a return to normal
What is the significance of a normal TSH level in a patient with thyrotoxicosis?
Inappropriate production of TSH
What is the diagnostic criterion for toxic adenomas?
Isolated elevation of serum T3 with autonomously functioning nodules
What is the significance of a suppressed TSH level in a patient with thyrotoxicosis?
Appropriate production of TSH
Study Notes
Thyroid Disorders
- Thyroid disorders involve alterations in metabolic stability due to thyroid hormone production or secretion.
- Symptoms include fever, malaise, myalgia, and signs of thyrotoxicosis.
Thyrotoxicosis
- Characterized by decompensated thyrotoxicosis, high fever, tachycardia, tachypnea, dehydration, delirium, coma, nausea, vomiting, and diarrhea.
- Precipitating factors include infection, trauma, surgery, radioactive iodine treatment, and withdrawal from antithyroid drugs.
- Symptoms: nervousness, anxiety, palpitations, emotional lability, easy fatigability, heat intolerance, weight loss, and increased frequency of bowel movements.
- Physical signs: warm, smooth, moist skin, fine hair, onycholysis, lid lag, tachycardia, widened pulse pressure, and systolic ejection murmur.
Thyroid Hormone Physiology
- Thyroxine (T4) and triiodothyronine (T3) are formed within thyroglobulin, a large glycoprotein synthesized in the thyroid cell.
- Inorganic iodide enters the thyroid follicular cell, is oxidized by thyroid peroxidase, and covalently bound to tyrosine residues of thyroglobulin.
- Iodinated tyrosine residues combine to form iodothyronines, with T4 formed from two molecules of DIT and T3 formed from MIT and DIT.
- Proteolysis releases thyroid hormone into the bloodstream, where it is transported by thyroid binding globulin (TBG), transthyretin, and albumin.
- Only unbound (free) thyroid hormone can diffuse into cells, elicit biologic effects, and regulate TSH secretion from the pituitary.
Thyroiditis
- Painless thyroiditis has a triphasic course, mimicking painful subacute thyroiditis.
- Presents with mild thyrotoxic symptoms, lid retraction, and lid lag, but absent exophthalmos.
- Thyroid gland is diffusely enlarged without tenderness.
- Painful subacute thyroiditis often develops after a viral syndrome, but rarely has a specific virus identified in thyroid parenchyma.
Diagnosis
- Elevated 24-hour RAIU indicates true hyperthyroidism, with the patient's thyroid gland overproducing T4, T3, or both.
- Low RAIU indicates excess thyroid hormone is not caused by thyroid gland hyperfunction, but by thyroiditis, struma ovarii, follicular cancer, or exogenous thyroid hormone ingestion.
- In thyrotoxic Graves' disease, there is an increase in overall hormone production rate, with a disproportionate increase in T3 relative to T4.
- Measurement of serum free T4, total T4, total T3, and TSH confirms the diagnosis of thyrotoxicosis.
This quiz covers the symptoms and characteristics of thyroiditis and thyroid storm, including systemic symptoms, physical examination findings, and presentations of thyrotoxicosis.
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